Contact - (IFHT), RWTH Aachen

Transcrição

2010
Annual Report
A NNUAL R EPORT 2010
1
Institute for High Voltage Technology
Schinkelstraße 2
DE-52056 Aachen
Phone:
Fax:
e-mail:
Internet:
+49 241 80-94931
+49 241 80-92135
[email protected]
www.ifht.rwth-aachen.de
Editor:
Univ.-Prof. Dr.-Ing. Armin Schnettler
RWTH Aachen University
Editorial:
Editorial deadline:
Dipl.-Ing. A. Strauchs, Dipl.-Gwl. M. Keller
31.12.2010
2
Preface
Research at IFHT
Fields of Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Scientific Reports of Research Group Circuit Breakers . . . . . . . . . . . . . . . . . . . . . . . . 12
Scientific Reports of Research Group Insulation Systems and Diagnosis . . . . . . . . 19
Scientific Reports of Research Group Sustainable Energy Systems . . . . . . . . . . . . . 32
Scientific Reports of Research Group Systems Engin. and Asset Management . . 45
Scientific Reports of Research Group Fault Arcs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
PhD Theses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
HumTec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Contents
Teaching at IFHT
Lectures and Laboratories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
Diploma- , Master-, Bachelor- and Project Theses . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Seminars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
The Institute
Chronicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Publications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Technical excursions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Service Portfolio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
EEIM Award 2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Staff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
112
116
121
129
130
134
138
3
4
Dear friends and partners of the Institute,
dear Ladies and Gentlemen,
recently electrical power engineering received an amount of attention from the media we dreamed about 20 years ago. However, this public attention leads to rushed
political actions and a complicated discourse about reasons, aims and solutions
towards alternative energy sources. Of
course we have to transform the existing
system according to the future needs. However, due to the high importance of reliable
and secured energy for the economy and
security for a country, this task must be
prepared thoroughly and rash experiments
and interference by political interests have
to be avoided.
In addition to the well-known aspects of
energy supply, such as security, reliability, sustainability and price, the aspect of
public acceptance gains more and more
importance. This is especially true for nonrenewable energies and for the necessary
measures for the reinforcement of the grid
which require a lot of persuasion of authorities and citizens before they can be
commissioned - if at all.
These developments prove that our holistic approach toward supplying electricity from concepts and scenario analyses over
technologies and systems to an economical,
ecological and ethical assessment of options - is a good one. We are convinced that
through our research topics and expertise
we are in a good position to contribute to
the future design and development of power
supply.
This annual report 2010, for the first time
in a separate German and English edition
is supposed to give you a short but concise
overview about our topics, research and results. To be able to maintain the format and
also accommodate the increased scope of
our topics and thus the increased number of
papers it became necessary to split the an-
nual report into a German and an English
edition.
My 10th year as head of the institute was
dominated by a growth of both personnel
and research topics:
• The money from third party funds
(i.e. non basic funds) spent in 2010
amounted to more than 3 million Euros with rising tendency.
• There were more than 250 oral exams in our core lectures and another
200 written exams in the Bachelor
study program.
• More than 60 theses (Bachelor, Master and Diploma) were submitted at
the IFHT.
• 17 Research associates were integrated to our staff (some temporarily).
• 8 members of our staff received
renowned awards.
• 5 dissertations were successfully
completed in 2010.
• A large number of new and interesting projects started or are in development.
We have to admit that these developments
in 2010, however positive they are, have
shown the limits of what is possible within
the environment of a university. The fact
that members of our staff received awards
despite their high workload makes us proud
and proves that growth does not necessarily compromises the quality of work - a very
important aspect for universities which are
usually not acquainted with strong growth.
The PhD degrees awarded to Dr. Kittipong Anantanavich, Dr. Ming Chark
Tang, Dr. Stefan Federlein, Dr. Michael
Keßler and Dr. Torsten Wirz made 2010
Preface
the implementation of the Testing center for
storage systems and Smart Grid technologiesänd social life at the Institute can be
found in this annual report. I want to thank
all friends and partners of the institute for
their support and suggestions and our staff
for their commitment and creativity.
We consider the success of the years past as
an acknowledgement of our work and as an
incentive for further improvement. Together
with you we want to find the solutions for
the future of our energy systems.
Best regards from Aachen Yours
also a successful year concerning our research. For the years to come we also
expect an annual average of five to six
PhDs. The works of Mrs. Anja Strauchs
and Mr. Andrey Mashkin in the field of
syntactic foam were acknowledged by the
IEEE DEIS Graduate Award and the EEIM
Award, respectively. For their theses Mr.
Daniel Eichhoff received the ABB-Diploma
Award, Philipp Masmeier the Otto-JunkerAward and Stanislav Votruba was granted
the SAG Award, 2nd grade. Especially
pleasant is the victory of our student project
„Plug into Future“ within the competition
„Energy for Ideas“ of the Federal ministry
for education and research (BMBF) which
was done by Bartholomäus Wasowicz and
Fabian Potratz in close cooperation with
Thomas Dederichs.
Information regarding teaching, research,
Aachen, January 2010
5
6
Research at IFHT
7
8
Fields of Research
Research Group “Circuit Breakers”
Manager: Dipl.-Ing. Andreas Kurz
Short description of the research topics:
Circuit breakers are one of the most important protective devices in electrical power
systems. Therefore, it is of huge importance to understand the physical process of a
switching operation. Thus, the research group follows two different approaches.
On the one hand so called CFD-(Computational-Fluid-Dynamics)-Simulations are used to
model the physical phenomena. Due to this information parameters can be figured out,
which are in general difficult to observe e. g. the temperature. On the other hand the
required equipment and know-how to investigate the phenomena experimentally is available
in the research group. While developing new switching technologies measurements of the
temperature, the pressure, the gas flow as well as a determination of the interruption limit
are part of the basic investigation methods.
Due to an intensive interaction of both approches some results could be transferred into
new inventions.
Members of the group:
Dipl.-Ing. Mathias Behle (until Mai) ∗ Dipl.-Ing. Daniel Eichhoff ∗ Dipl.-Ing. Matthias
Hoffacker ∗ Dipl.-Ing. Andreas Kurz ∗ Dipl.-Ing. Gregor Nikolic ∗ Dipl.-Ing. Ming-Chark
Tang (until April)
Student assistants:
Stefan Buß ∗ Polson Keeratibumrungpong ∗ Tim Kubiczek ∗ Andreas Meyer ∗ Thien-duc
Nguyen ∗ Gregor Nikolic ∗ Karl Oberdieck ∗ Michael Weuffel ∗ Tobias Wild
Research Group “Insulation Systems and Diagnosis”
Manager: Dr.-Ing. Michael Keßler
The research group covers a wide variety of technical challenges: ranging from the development of new insulating materials, up to a condition assessment of insulating systems by
means of different diagnostic methods. In the field of hybrid insulation systems, syntactic
foam as a new insulating material with low specific density is in the main focus. Especially
a possible correlation of the dielectric strength and the adhesion between microspheres as
filler and the matrix is investigated. In the field of diagnosis, the assessment of polymeric
insulation systems by using ultra sound is another focus. Besides the detection of small impurities in different materials like elastomers (e.g. in cable joints), boundary layers between
two different materials and inhomogeneous cross-linking are detectable. A new application
of ultra sound diagnosis is the temperature measurement at inner interfaces.
An efficiency advancement of ignition systems in combustion engines via „Multisparc Ignition“ is a new research field of this group. Instead of one single sparc, many short discharges
are ignited in series to assure a steady ignition of the fuel-air mixture.
Fields of Research
Research Group “Sustainable Energy Systems”
Manager: Dipl.-Ing. Dipl.-Wirt.Ing. Thomas Dederichs
The research group is focused on modelling and assessing integrated energy systems. These
systems are characterized by merging the markets for different forms of energy due to technological developments (e.g. Combined Heat & Power, heat pumps or electric vehicles).
The expertise of the group lies especially in generation, transmission and distribution technologies. The methods implemented in the process of modelling include classic scenario
analysis, load flow and stability assessments as well as economical analyses (for example
potential or risk assessment). This is complemented by extensive knowledge in the field of
Life Cycle Assessment according to ISO 14040/44.
Sustainability is perceived as a multi-crtiteria optimization problem, which must include
technical, economical, and ecological assessment criteria. Much effort is directed into supporting the further development of a methodology for technical eco-efficieny analysis. Due
to the close cooperation with the interdicipinary project house “Humtec“ in the field of
„Ethics for Energy Technologies“ the research is rounded off by taking ethical problems
into consideration.
Dipl.-Ing. Dipl.-Wirt.-Ing. Thomas Dederichs ∗ Dipl.-Ing. Dipl.-Wirt.-Ing. Markus Gödde
∗ Dipl.-Ing. Thomas Helmschrott ∗ Dipl.-Ing. Stefan Krengel ∗ Dipl.-Ing. Claas Matrose
∗ Dipl.-Ing. Hendrik Natemeyer ∗ Dipl.-Wirt.-Ing. Baris Özalay ∗ M. Sc. Thomas Pollok
∗ Dipl.-Ing. Martin Scheufen ∗ Dipl.-Wirt.-Ing. Eva Szczechowicz ∗ Dipl.-Wirt.-Ing.
Bartholomäus Wasowicz ∗ Dipl.-Ing. Sebastian Winter
Student assistants:
Mitra Ariatabar ∗ Reinhold Bertram ∗ Christian Bredtmann ∗ Philipp Erlinghagen ∗ Pascal Golor ∗ Philipp Grüneberg ∗ Andreas Haidl ∗ Mirco Hinnenkamp ∗ Julie Kramer ∗
Sören Kreimeier ∗ Shanta Kumar ∗ Julian Langstädtler ∗ Moritz Mittelstaedt ∗ Mark Müller
Giebeler ∗ Thomas Nemeth ∗ Florian Nießen ∗ Tim Noffz ∗ Jens Noschinski ∗ Cora Sophie
Petino ∗ Fabian Potratz ∗ Stephan Raths ∗ Erik Reimann ∗ Annika Reitz ∗ Andreas Roehder
∗ Yvonne Surmann ∗ Julia Tecklenburg ∗ Philipp Tünnerhoff ∗ Johannes Turinsky ∗ Markus
vor dem Berge
Dipl.-Ing. Gregor Brammer ∗ Dr.-Ing. Michael Keßler ∗ Dipl.-Ing. Jens Knauel ∗ M. Sc.
Andrey Mashkin ∗ Dipl.-Ing. Benjamin Preidecker (Daimler AG) ∗ Dipl.-Ing. Christoph
Roggendorf ∗ Dipl.-Ing. Anja Strauchs ∗ Dipl.-Ing. Daniel Winkel
Student assistants:
Denys Demenko ∗ Paul Duisberg ∗ Henning Frechen ∗ Pierre Honoré ∗ Sebastian Kamps
∗ Patrick Poss ∗ Alexa Rombach ∗ Christoph Schneider ∗ Stefan Seibel ∗ Daniel Vobis ∗
André Wagner ∗ Matthias Wiesmann ∗ Serdar Yildiz
9
10
Research Group “Systems Engineering and Asset Management”
Manager: Dipl.-Ing. Christian Hille
A safe, reliable and efficient operation of electrical grids is the main focus of the research
group Systems Engineering and Asset Management. This task requires a fundamental and
detailed knowledge of the behaviour of each relevant grid component, in order to be able
to model the complex system’s behaviour. Additionally, the system point of view enables
identification and description of emergent properties.
Current and future performance, reliability and lifetime of installed equipment are assessed
in close cooperation with grid operators and manufacturers. The main focus is the
development of asset-simulation software and expert-systems to support grid operators in
their decisions towards an efficient network operation.
Protection systems of actual and future distribution networks are presently another focus.
A massive penetration with decentralized energy resources and accumulators falsifies
classical assumptions concerning the distribution systems’ operating conditions. Protection
systems are analyzed and designed from an integral point of view, looking at the single
components’ and the system’s properties and behaviour at once. Thereby a secure operation
of today’s distribution networks and those of the future shall be guaranteed, also taking into
consideration the prospective long term coexistence of future’s active and classic passive
distribution systems. A technological and economic comparison of different options shall
enable macroeconomic optimal recommendations.
M. Sc. Tirinya Cheumchit ∗ Dipl.-Ing. Stylianos Filippidis ∗ Dipl.-Ing. Christian Hille ∗
Dipl.-Ing. Tilman Wippenbeck
Student assistants:
Tim Gaßmann ∗ Karina Klusmann ∗ Pascal Koehn ∗ Simon Sandor
Field of Instruction and Research
“Gas Discharge Engineering”
Univ.-Prof. Dr. rer. nat. Gerhard Pietsch
Fault arcs in electrical installations cause temperature and pressure rise in switchgears and
switchgear buildings. In principle, fault arc safety can be proved experimentally by fault arc
tests and theoretically by pressure rise calculations. The advantage of pressure rise calculation is that it can be performed with applications, for which no experimental possibilities
are available, e.g. when the influence of pressure rise on buildings is investigated during the
design of a substation. The existing pressure calculation methods will be extended particularly for SF6 -insulated installations. In this case, changing SF6 -air mixtures in the relief
room have to be taken into account. The extended calculation method can be evaluated by
comparing calculated with experimental results. A further problem is related to the replacement of SF6 by air for tests of SF6 -insulated switchgear due to environmental concern. This
Fields of Research
M. Sc. Kittipong Anantavanich
task is to find out, whether there exist possibilities to replace tests with SF6 by those with
air.
11
Development of a measuring system investigating the spatial resistance distribution
of switching arcs
For many years the development of gas circuit breakers is surrounded by computational
fluid dynamics simulations. They can help to unterstand and thus to improve the switching
process of the breaker. The used physical models of these simulations are often crosschecked
by experimental investigations. The spatial arc resistance distribution of the arc is one of the
fundamental aspects which are related to the interruption capability of the circuit breaker.
However it could not yet be determined by experiments as all known methods have either a
influence on the arc and the gas flow or can only applied at special conditions. The aim of
the ongoing research project is the development of a new method to determine the spatial
arc resistance distribution of a quenched switching arc. This can lead to a better physical
understanding of the cooling process and thus to improved simuilation models.
Introduction
12
Circuit breakers are important for the electric energy supply. They are responsible for
disconnecting the current at nominal conditions and in case of a fault. The current is interrupted during its natural current zero crossing by cooling the electric
arc. This cooling is established by blowing
the arc with the filling gas of the breaker.
For a SF6 circuit breaker the arc resistance
at a time instant 200 ns before current zero (R200) can be used as an indication to
predict the success of the interruption capability [1]. Different cooling mechanisms
along the axis of the arc cause a non-linear
resistance distribution in the arc. The measurement of this distribution would render
possible a conclusion on these mechanisms
and their influence on the interruption capability [2]. Thus a non-invasive method to
determine this spatial resistance distribution of a blown switching arc is the objective
of this project.
Approach
For the measurement of the spatial arc resistance distribution the potential drop along
the axis of the arc is determined. The arc
resistance distribution is then calculated by
knowing the current. The potential distribution will be determined by measuring the
electric field surrounding the arc. Therefore a reference potential is required which
is created by mounting a conductive cylinder around the insulation nozzle. The cylinder is then connected to ground. Measuring
electrodes are placed between this cylinder
and the nozzle (Fig. 1) to measure the arc
potential.
measuring electrode
PP
PP
PP
q
P
C1
Ce
cladding electrode
Ci
Cn
Ri
Fig. 1: Measuring principle (schematic)
The material of the nozzle acts as a dielectric and separates the electrode from the arc.
This construction is a capacitive field probe.
Between electrode and grounded cladding
tube a capacity Ce is generated. Furthermore this yields to different stray capacitances
Ci between arc and measuring electrode.
The sum of all these capacitances C1 ...Cn
Field of Research: Circuit Breakers
ϕ1
C1
I1
..
ϕi
Ci
Influence of radius and position of the
arc
Using a capacitive coupling, correct dimensions of the field probe and a well chosen
load of the sensor the electric field strength
at the wall of the conductive cladding tube can be determined [3]. Assuming a short
part of the arc with the length ∆x is an ideal cylindric conducter with the radius rarc
the measured field strength can be calulated
analogue to a cylindrical capacitance:
Ii
..
ϕn
Cn
In
Ce
ln
Rm
Cm
Um
Fig. 2: Model of capacitive coupling
In Fig. 2 the mathematical model of the signal coupling of a sensor loaded with Rm
and Cm is given. With given arc potentials
ϕi the measured voltage at the sensor electrode is calculated by:
Um =
Cm +
Pn
Pi=1
n
Ci ϕi
i=1 Ci
−
ϕ
E0 ∝
Im
j
Rm ω
By knowing the signal of multiple sensors
the arc resistance distribution can be calculated. Therefore the potential of the arc in
front of the sensor should have the highest
influence on the measured voltage. Thus
the coupling capacitance Ci which is lineal
from sensor to arc should have a high value
while the capacitances beside should have
low values. This can be established by design features. To achieve a linear frequency
response of the transfer function of the system the load resistance Rm has to be as
high as possible with respect to the band
width of the signal to be measured.
r0
rarc
is the coupling capacitance between sensor
and arc. The setup corresponds to a capacitive divider with Ci as the upper capacitance of the divider and Ce as lower capacitance of the divider. For measuring the potential distribution several sensors are located along the axis of the arc. Each sensor is
measuring a partial voltage of the arc.
∗ r0
Here ϕ is the potential of the part of the arc
and r0 is the radius of the cladding tube.
Obviously neither ϕ nor rarc can be determined by knowing r0 and E0 . The assumption of a constant value for rarc is not valid
as the arc radius will vary due to its dependence on the quenching and on the current.
By means of a second field probe - which
is assembled at the same part of the arc with a radius r1 unlike r0 the electric field
strength E1 can be calculated analogue.
Thus both unknown variables (ϕ und rarc )
can be determined. However the assumed
symmetry along the rotational axis will not
occur in the experiment. The arc will move
inside the insulation nozzle. Hence r0 and
r1 as well are unknown. To be able to determine position, thickness and potential of
the arc anyway the amount of field probes is
increased. By placing four sensors surrounding the same short part of the arc the system of equations can be solved.
Results
In a first approach four capacitive coupled
sensors are placed around an arc burning
inside a insulation nozzle. The design is
shown in fig. 3. Three sensors are identical
and separated by an angle of 120◦ from each
13
other (S1-S3). The forth sensor (S4) is shifted outwards.
S1
S2
S3
Acknowledgement
S4
This Project is funded by Deutsche Forschungsgemeinschaft (DFG).
Fig. 3: Sensor arrangement
The feasibility of the above explained measurement method can be shown by experiments. The measured voltages at sensors S3
and S4 for a non-quenched arc - which is
powered by a 950 Hz resonance circuit - are
shown in fig. 4.
0.06
S3
S4 +8,6dB
0.04
0.02
sensorvoltage [V]
0
14
ple groups - each consisting of four sensors
- along the axis of the arc. For analysing
the experimentally measured data a software is developed to calculate the spatial resistance distribution. Therefore the mathematic theory of inverse problems is used.
-0.02
-0.04
-0.06
-0.08
-0.1
-0.12
-0.14
19
19.5
20
20.5
21
21.5
Zeit [ms]
22
22.5
23
Fig. 4: Measured sensorsignal
Here the signal amplitude of sensor S4 is
amplified by 8.6 dB. This allows a qualitative comparison between both voltages.
Differences between both voltage characteristics can be explained by a varying arcradius respectively by a changing arc position.
Outlook
As the principle feasibility of the method
can be shown the next step is placing multi-
References
[1] Knobloch, H., Habedank, U.: Behaviour of SF6 high-voltage circuit breakers with different arcextinguishing systems at shortline
fault switching; In: Science, Measurement and Technology; IEE Proceedings; Bd. 148 273−279; 2001
[2] Tang, M.C.: Widerstandsverteilung
in Schaltlichtbögen von Selbstblasleistungsschaltern während der
Stromnulldurchgangsphase; Dissertation, Institut für Hochspannungstechnik; RWTH Aachen; 2010
[3] Andreas Küchler: Erfassung transienter elektromagnetischer Feldverteilungen mit konzentrierten und
räumlich ausgedehnten Sensoren;
Fortschritt-Berichte VDI; Reihe 21:
7; Düsseldorf; 1986
Contact
Dipl.-Ing. Matthias Hoffacker
[email protected]
+49 241 80-94944
In future electrical power systems based on DC-technology (direct current) appropriate
switchgears are essential for switching operations during normal conditions as well as in
case of fault conditions. AC-circuit breakers, widely used in present grids, are unable to
perform these operations due to their basic physical process of ’current zero switching’.
Hence, the development of special DC-circuit breakers is necessary. For this purpose, firstly,
the technical requirements must be determined by means of simulations. It is observed, that
fault currents in a DC-grid rises with a higher steepness compared to AC-systems with
similar short circuit power. Concerning the interrupting capability, this means that DCcircuit breakers generally have to fulfill enhanced requirements.
Introduction
In the future, the DC-technology will be increasingly used in electric power systems.
At present, the HVDC-technology is already used for the energy transmission over
long distances and for the connection between offshore windfarms and the onshoregrid. In many cases of application, HVDC
is the only reasonable alternative [1].
In electric distribution grids, the share of
converter-connected, decentralized power
generation units, especially photovoltaic
units and wind energy converters, will
further increase as well as the ratio of
converter-fed loads in the grid will rise.
Hence, the DC-technology can be advantageous for medium-voltage distribution grids regarding technical and economical issues [2]. The realization of
the internal medium-voltage grid in an
offshore-windfarm is assessed as a possible application for a medium-voltage DCgrid (MVDC), which interconnects the dcbusses of the wind energy converter (WEC)
units with the central HVDC-platform [3].
In this way, the convertion to the 50 Hz
AC-voltage at the WEC units, the transformation of the 50 Hz current and the rectification for the HVDC-connection can be
avoided.
These MVDC-grids require appropriate
switchgears in form of DC-circuit breakers
for a reliable and save operation. These
circuit breakers must be able to perform
the switching of nominal currents under
normal operation and they have to assure
the save interruption of short circuit currents in case of a fault. At present, appropriate circuit breakers are not available
for MVDC-applications. Furthermore, ACcircuit breakers are not suited for the interruption of direct currents, as they essentially require a zero-crossing of the current, which does not occur in the DC-case.
For a targeted development of the needed
DC-circuit breakers, firstly, the technical
requirements for these switchgear, which
arise in future DC-grids, have to be identified. Technical standards, providing applicable figures and values, have not yet been
defined.
Model of a MVDC-Grid
The technical requirements for DC-circuit
breakers can be derived from theoretical investigations in a model DC-grid.
The bipolar MVDC-grid in an offshorewindfarm, which is used for the simulations, is given in Fig. 1. The nominal
voltage of the exemplary system is set to
+/- 7,5 kV. For reasons of clarity, only one
single pole of the system and one branch
Technical requirements for
circuit breakers in future DC grids
15
16
of the grid are depicted. The grid links
the wind energy concerter units (WEC),
having a nominal power of 5 MVA each,
with the central DC/DC-converter platform,
from where the electric power is transmitted to the onshore grid by a HVDC-link.
In normal operation the mechanical switch
carries the current due to its comparatively
low losses. To interrupt the current, the
mechanical switching contacts are opened
and simultaneously, the anti-parallel thyristors are fired. Hence the current commutates into the parallel path and charges the
capacitor. If the charging voltage of the
capacitor exceeds the grid voltage, a negative di/dt is applied over the grid inductances (maily the inductances of the cables in the grid). This leads to a decrease
and finally to an interruption of the current. The varistor limits the maximum
charging voltage to its residual voltage.
Fig. 1: Model of the DC-Grid for a OffshoreWindpark
One possible fault, considered in the model
of the DC-grid, is given by an earth fault of
the cable L3. In this case, the circuit breakers CB1 and CB2 as the responsible protective devices have to interrupt the fault current.
Technically, different concepts exist, how
a DC-circuit breaker can be realized.
Whereas special requirements in addition
to general ones can arise for every breaker
topology. In the scope of the presented
simulations a Snubbered Mechanical Circuit Breaker (SMCB) is investigated. The
SMCB is a so-called hybird circuit breaker,
that combines a mechanical switch with
powerelectronic devices and passive components, as shown in Fig. 2. The main features of the SMCB are its simple control
and the utilization of cost-effective thyristors instead of active-turn-off devices like
IGBTs [4].
Fig. 2: Setup of a Snubbered Mechanical Circuit Breakers (SMCB)
Exemplary results
The presented exemplary results are based
on the application of a SMCB-model, used
to interrupt an ideal earth fault in the model
DC-grid. Before the fault occurs at t = 0 s,
the system operates with a nominal current of 1 kA. The simulated development of
the current through the breaker, the voltage
over the breaker, and the grid voltage during the switching process are given in Fig.
3˙Immediately after the occurance of the
fault, the current increases with a rate of rise
up to 75.4 A/µs and crosses the detection
level of 2 kA after 18.5 µs. The internal delay of the breaker after the detection of the
fault is assumed to be an additional 100 µs.
Current mech. switch
8
Current I [kA]
Current parallel path
6
Current Varistor
4
2
0
0
100
200
300
Time t [µs]
400
500
12
Voltage U [kV]
10
Voltage over circuit breaker
8
Wmag =
6
4
Grid voltage
2
0
0
100
200
300
Time t [µs]
400
500
Fig. 3: Current and voltage during the clearing
of the earth fault
After the separation of the mechanical contacts, the current commutates into the parallel path and reaches a maximum value of
8.8 kA after t = 140 µs, when the charging
voltage of the capacitor in the breaker UC
exceeds the voltage of the grid. The voltage
UC further increases and is limited by the
varistor after 170 µs to a maximum value
of 11 kV. In this phase the current commutates into the varistor path. With the preset
parameters for the grid and the SMCB the
entire interruption process is completed after 270 µs. The system voltage, which dips
down to 2.0 kV during the fault, recovers to
its nominal value of 7.5 kV after the successful disconnection of the fault affected
section of the grid.
The increasing voltage over the capacitor
due to the charging by the commutated current leads to a dielectric stress of the contact gap in the mechanical switch immediately after the contact separation. In order
10
to avoid a dielectric breakdown and hence a
failure of the entire breaker, the stress of the
contact gap must be controlled by a sufficient dielectric strength of the gap. Because
the mechanical contact are still in the opening process and have not reached the maximum contact travel, a voltage rise of less
than 1 kV/µs can already cause a dielectric
stress, which may lead to a breakdown [5].
Hence. the rate of rise of the voltage over
the breaker has to be considered in the dimensioning process of the capacity.
The energy stored in the grid in form of
magnetic energy
1
2
· Lgrid · Imax
2
is compensated by the breaker during the
switching process, This is done, firstly, by
charging the capacitor and secondly, by the
dissipation of ohmic losses, especially in
the varistor. The maximum amout of energy, which has to be compensated, must
be taken under consideration during the development of a DC circuit breaker as an
additional parameter.
Conclusion
and Outlook
The behaviour of a DC-grid under fault conditions and the subsequent electric stresses
for circuit breakers during the interruption
of fault currents deviates inherently from
the situation in present AC-grids. The DCcircuit breakers have to fulfill increased
technical requirements concerning their interruption capability, which arise from the
lack of natural current zero crossings and
the high steepness of the DC-fault current.
The dielectric stress of the breaker by a
transient recovery voltage (TRV) after the
current interruption, as in high voltage ACsystems, does not occur in the DC-case. In
fact, the DC-circuit breaker is dielectrically
stressed by the voltage that is internally
17
18
build up during the switching process to
achieve a negative di/dt over the grid inductance. Additionally, the DC circuit breaker
must be able to compensate the magnetically stored energy from the grid.
The investigations show that DC-grids require high performing protection technologies and secondary installations, especially
concerning the required speed of the fault
detection, the signal processing and the signal transmission. The value of 100 µs,
which is assumed for the entire time delay
in the scope of the current investigations, is
less than the operational time present technology can provide.
The technical requirements derived from
the current investigations will be used for
the development of a DC-circuit breaker
for MVDC applications. For this purpose,
the SMCB will be compared with several
concepts for DC-circuit breakers, that use
vacuum switching technology in order to
identify the most qualified topology, which
will be used as a basis for the design of a
MVDC cricuit breaker prototype. With regard to the vacuum circuit breaker, the effect of current chopping on the dielectric
stress of the DC-grid and the DC-circuit
breaker will be analyzed. Additionally, the
required equipment for development and
performance tests of DC circuit breakers
will be setup according to the simulative results from these investigations.
References
[1] Kirby, N. et al: HVDC transmission
for large offshore wind farms, IEE
Power Engineering Journal, Vol 16,
pp.153-141,2002
[2] Larruskain, D. et al: Transmission and Distribution Networks: AC
versus DC, 9th Spanish-Portugese
Congress on Electrical engineering,
Marbella, Spain, 2005
[3] Martander, O.: Wind Farm Configuration and Energy Efficiency Studies - Series DC versus AC Layouts, Chalmers University Göteborg,
Ph.D. Thesis, 2006
[4] Meyer, C.:
Key Components
for Future Offshore DC Grids,
RWTH Aachen University, Aachener Beiträge des ISEA Band 46,
Ph.D. Thesis, 2007
[5] Holaus, W.: Ultra fast switchesBasic elements for future medium
voltage switchgear, Swiss Federal Institute of Technology Zurich
(ETH), Ph.D. Thesis, 2001
Contact
Dipl.-Ing. Daniel Eichhoff
[email protected]
+49 241 80-97348
Dipl.-Ing. Andreas Kurz
[email protected]
+49 241 80-90270
Field of Research: Insulation Systems & Diagnosis
Many parameters of the cable production process are based on long experiences and are
optimized for every special cable type. During the combined extrusion process of the cable
sheath, there is a risk that gas inclusions can occur between the polyethylene sheath and
aluminium screen caused by missing glue. Due to those inclusions water can permeate
into this delaminated areas and can cause corrosion of the aluminium screen, which leads
to reduced life time of the cable. With ultrasound diagnosis it is possible to identify and
localize these gas inclusions at interfaces.
Delaminations in power cables
Theory of detection
In the last production step of power cables for high voltage (HV) and extra high
voltage (EHV) an aluminium screen is bent
around the cable core and both ends are
welded together.
A sound impulse propagating from the
transducer (TD) through the sample is reflected at innner interfaces and at the backwall and propagates back to the transducer which receives the impulse (Fig. 1).
The screen shall carry the short circuit
current in a fault situation and prevent water
intrusion into the cable, which could lead to
chemical degradation of the insulation material.
After welding, the screen is led into
the extruder head. Inside the head the hot
screen is covered with a thin glue layer and
a polyethylene (PE) sheath is extruded on
top. There is a risk for delaminations during
the sheathing process of the cable. Water
can permeate into these delaminations and
cause corrosion of the screen. Due to the by
corrosion reduced cross sectional area the
ampacity might be influenced negatively. It
is possible to perform a non-destructive online test of the interface between the aluminium screen and the polyethylene sheath
directly after the extrusion process for detection and localization of potential defects.
The positive aspect about this monitoring
is the knowledge of the defect’s position.
Moreover it gives the chance to optimize
the production parameters during the running extrusion process of the sheathing line.
Hence rejections can be minimized.
Prototype for detection of delamination
in power cables using ultrasonic diagnosis
19
Fig. 1: Top: Sound propagation and reflection
at inner interfaces
Bottom: Time signal of the reflected impulses
A reflection of waves occurs generally at interfaces between two materials with a different specific sound impedance Z which is
defined as product of density ρ and sound
velocity c of the material:
Z =ρ·c
The sound waves behave at material boundaries corresponding to the mathematical
model of electrical waves. The reflection
and transmission coefficients are given by
[1]:
Z2 − Z1
R=
Z2 + Z1
2 Z2
T =
Z2 + Z1
where Z1,2 are the specific sound
impedances of the materials. In order
to detect delaminated areas of the cable sheath the time signal of the ultrasound reflection is analysed. In figure 2
the intact reflection signal (black) is compared to the signal of an air inclusion
(gray). The difference between these signals can be found by correlating the measured time signal with a reference signal.
1000
amplitude / a.u.
500
0
−500
20
−1000
100
200
300
400
time / a.u.
500
600
Experimental Setup
In a first step an applicative test bench
with a single transducer for testing of the
interface between aluminium screen and
polyethylene sheath is build up. This setup
is used for verification of the theory of detection of gas inclusions at the interface
for this special kind of cable sheath. Figure 3 shows the test bench with a sheath
sample mounted. The setup uses a single transducer for scanning. The ultrasonic
transducer is mounted on a special construction which provides a water reservoir
for coupling the ultrasound into the sample. For the movement of the sample and
the transducer a micro positioning system
is used. While moving the transducer continuously along the sample the ultrasonic
signal is recorded. At the end of every
line the sample is rotated. A combination
of the ultrasonic measurement data and the
measurement position gives the possibility
for location of defects at the interface between aluminium screen and the polyethylene sheath within the scanned sample.
Fig. 2: Time signal of synthetic testsample,
black: intact, gray: delamination
Using signal correlation the differences in
ultrasonic signals can be evaluated automatically after or even during measurement.
The similarity of two signals s(t) and g(t)
is described by the normalized cross correlation function [2]:
psg =
R +∞
−∞
s∗ (t) g(t − τ )dt
p
Es Eg
To make the result independent from the
particular energy of the signals s(t) and
g(t) it is normalized, where Es and Eg are
the energies of the signals. As a result psg
returns values in the range of -1 to +1 where
+1 is the largest similarity.
Fig. 3: Experimental setup for automated scanning
The measurement data collected during
the scanning process are stored for investigations on the acoustic properties of the
sheath material, post processing and analysis as well as the development of a detection algorithm. Figure 4 shows a K-scan
[3], a 2d-plot of the correlation coefficients
depending on the position. Black areas rep-
180
0.8
160
0.6
φ direction / a.u.
140
0.4
120
0.2
100
0
80
−0.2
60
−0.4
40
−0.6
20
−0.8
20
40
60
80
x direction / a.u.
100
120
It is possible to correlate the measured data
to a certain position of the cable which
enables the possibility for finding the delaminated areas. The online evaluation and
data analysis allows a direct user interaction
e. g. display of a warning if delaminations
are detected. Using this information given
by the ultrasound measurement system it
is possible to mark the delaminated areas
and to correct production parameters, in order to guarantee a constant quality of the
power cable sheath and a minimization of
rejections.
−1
Fig. 4: Scan of synthetic testsample,
black: intact, white: delamination
Industrial Prototype
The developed ultrasound measurement prototype is an adaptive system, which can be used in the production line without changing the existing production process (Fig. 5).
Acknowledgement
The authors thank NEXANS Charleroi/Calais
for the good cooperation and the preparation of special sheath samples.
References
[1] Werkstoffprüfung mit Ultraschall,
J. Krautkrämer, H. Krautkrämer,
Springer 1986
[2] Signalübertragung, J. R. Ohm, H. D.
Lüke, Springer 2004
[3] Detektion und Evaluation von Inhomogenitäten im Volumen und an
inneren Grenzflächen in polymeren
Isoliersystemen mittels Ultraschall,
P. Walter, Dissertation IFHT, Aachen
2006
Fig. 5: Multisensoral transducer arrangement
Moreover the measurement technique is
contactless so that there is no need for a
physical contact between the system itself
and the extruded cable sheath. This ensures a non-destructive examination of the
extruded PE sheath. In order to cover the
surface of the cable several ultrasound sensors are placed around the cable sheath.
resent an intact interface between the aluminum screen and the PE sheath. Delaminations show less similarity to the reference
signal and are therefore coloured in white.
Contact
Dipl.-Ing. Gregor Brammer
[email protected]
+49 241 80-94910
Dipl.-Ing. Jens Knauel
[email protected]
+49 241 80-97346
21
Design and Construction of a Test Bench
to Characterize the Behavior of Batteries in
High Voltage Storage Systems
Battery energy storage systems could be able to compensate volatile energy sources, such
as wind and solar energy. One system topology for medium voltage grids uses high voltage
batteries. This concept should provide an improvement of the overall system efficiency.
High voltage batteries may be advantageous for future DC-grids as well. However, as there
is little expertise about series-connected batteries up to several kilovolt, the charging and
discharging behavior of such systems will be investigated. For this purpose, a test bench
for high voltage storage systems is built to analyze these processes for different battery
technologies.
Introduction
22
Strongly increasing power generation based
on volatile energy sources, such as wind
and solar energy, sets new requirements on
design, planning and operation of power
systems. In addition, the demand for regulating reserve power and ancillary services
is drastically increasing, forcing power system operators to intensify the use of system
flexibility measures and non conventional
operating concepts. Here, battery energy
storage systems or electrochemical energy
storage systems in general may offer unique
and scalable solutions for high power and
long term energy demands in the range of
up to 100 MW and several 100 MWh.
To reach these power levels one option is
to use high voltage storage systems. Large
battery energy storage systems show high
reliability and robustness. Thus, the usage
in high voltage applications is feasible in
general [1]. However, the series connection
of batteries up to several kilovolt leads to
nontrivial charging and discharging characteristics of such a storage system. To investigate the cell balancing behavior for different battery technologies, a high voltage battery test bench is under construction. The
concept of the test bench is shown in Fig. 1.
Fig. 1: Principle drawing of the test bench
The test bench consists of an insulation
transformer with connection to the low voltage grid, an inverter, a DC/DC converter as
charge/discharge unit and the high voltage
storage system. The power capacity of the
power electronics and the grid connection is
in the range of 100 kVA. In the basic configuration the storage system consists of 360
lead-acid batteries (12 V / block) connected
in series.
Power electronics
The classical two-level hard-switched converter is state-of-the-art for low voltage applications, being the most commonly used
topology in industry. For grid connection
of such converter it is necessary to have a
higher dc-link voltage than it is usually used
for drives, in order to be able to inject power
into the grid. The converter is connected to
the 50 Hz low voltage grid. The converter’s
switching frequency is 3 kHz. In order to
comply with the grid codes, an LCL output
High voltage storage system
The battery storage system consists of a
large number of cells in series, thus the optimum topology and reliability are major
issues. Lead-acid batteries are robust and
competitively priced in comparison to other
battery technologies. The test bench’s battery is constructed of 360 12 V lead-acid
blocks, with a capacity of 27 Ah each. The
test bench’s battery system can store approximately 120 kWh of electrical energy.
The topology of the test bench mainly consists of six battery building blocks with
720 V each. Thus, the nominal string voltage is ± 2160 V. In the case of fully charged
batteries including the voltage drops over
the cables, fuses and disconnectors the
storage system voltage is about ± 3 kV.
Figure 2 shows the battery storage system. Each battery building block consists of ten substrings of 72 V. The batteries in the test bench are stored in
two separate battery racks, each contain-
ing three of the 720 V building blocks.
This design was chosen to reduce connection length in order to decrease the
internal resistance of the storage system.
filter is used together with a current control
which is able to compensate low order harmonics.
The DC/DC converter, a dual-active bridge
topology, acts as a charging/discharging
unit for the high voltage battery. In the
test bench, there is a wide range of operation conditions. Depending on the charging status of the batteries, the voltage varies
between 3.3 kV and 6 kV. The charging/discharging power varies between 4 kW and
100 kW. Low power operation is needed to
investigate the voltage distribution of the
series connected battery cells. The converter is optimized for the whole operation
range. The output voltage is controlled by
the grid coupling inverter to be constantly
750 V. Hence, a high voltage transformation ratio from output to input is necessary.
Therefore, a galvanically isolated topology
was chosen to benefit from the winding ratio of the included transformer.
Fig. 2: Battery storage system
The battery monitoring system for the test
bench consists of 360 LEM Sentinel sensors. Herewith the voltage, temperature and
impedance of each battery block are measured independently.
Safety infrastructure
Due to the high voltage and the high energy, elaborate safety requirements for a
high voltage battery test bench are necessary. Therefore a special safety infrastructure is developed and integrated into the
system. In the laboratory operation regular maintenance and adaptation of the system is indispensable. In the special case
of the high voltage storage system it is not
possible to switch off or to ground the high
voltage. The maximum DC touch voltage
is 120 V [2]. Therefore, within the safety
infrastructure the high voltage storage system can be separated into battery stacks
of 72 V. To avoid long wiring distances a
special disconnector system, which is di-
23
rectly constructed into the battery shelves,
was developed. Figure 3 shows the principle of these disconnectors for the first
two levels of the battery rack. All in all,
60 disconnectors are realized in this way.
and the wide operation range of the power
electronics in the test bench allow a variation of different parameters to find the optimal topology. For example it will be possible to adapt the voltage level of the storage
system and to investigate the charging and
discharging behavior for other battery technologies by replacing some of the lead-acid
battery strings. The usage of battery storage
systems in medium voltage grids requires
a high reliability of the system. Therefore,
with the monitoring systems for each 12 V
block a detailed examination of possible
failures within high voltage storage systems
can be performed. In addition, a connection
of some battery strings in parallel allows a
reliability analysis of redundant topologies.
Acknowledgment
Fig. 3: Disconnector system in the battery
shelve
24
The control of power electronics, the battery monitoring, as well as the door of the
safety cage, emergency switches and smoke
detectors are integrated into the safety circuit. Hence, monitoring all critical conditions is possible. In case of emergency the
test bench can be switched into a secured
status.
Intended investigations
In the presented test bench it is possible
to investigate the charging/discharging behavior of different battery technologies in a
high voltage series connection. Efficiency
and reliability of such a system are of special interest and can be investigated with
the described set-up. The main focus is on
the necessary measures for cell balancing
in series connected batteries. The modular construction of the high voltage battery
The project this report is based on was
funded by E.ON AG as part of the E.ON
Research Initiative.
References
[1] P. A. Taylor, Update on the Puerto
Rico electric power authority’s spinning reserve battery system, Battery
Conference on Applications and Advances, 11th Annual , pp. 249-252,
1996
[2] IEC 60364-4-41, Protection for
safety - Protection against electric
shock, International standard, 2007
Contact
Dipl.-Ing. Christoph Roggendorf
[email protected]
+49 241 80-93032
The current activities deal with the experimental and theoretical investigation of syntactic
foam. The investigation focuses on the impact of temperature and electrical dc field stress
on the conductivity and breakdown strength of this kind of material. As a main result an
exponential dependency of the material’s conductivity on temperature and electrical field
stress can be determined. Furthermore, in a limited temperature range, an increase of
the electrical breakdown field strength with increasing temperature is observed. Above a
certain threshold temperature, the breakdown field strength decreases.
Introduction
Syntactic foam is a new composite material
consisting of hollow microspheres (HMS)
and a polymeric matrix. Due to its specific foam structure the material features a
very low density. In the present investigation syntactic foam of hollow glass micropsheres and an epoxy resin matrix is used.
Possible filling degrees of the hollow microspheres go up to 55 Vol.-% and reduce
the material’s weight by 40 % compared to
pure epoxy resin. Syntactic foam is already
successfully used as insulation material in
high voltage components, where a compact
and lightweight design is required. Fig. 1
shows a Scanning Electron Microscopy picture of the material. The name Syntactic foam origins from the specific material
structure, which differs from the structure
of conventional foamed polymers.
If an insulation system is stressed by an
electrical dc field, the field inside distributes
according to the conductivities of all materials used. Therefore, a detailed knowledge
of the conductivity and breakdown field
strength of each material or component is
required. For solid dielectrics, e.g. epoxy
resin, a correlation between the electrical
conductivity and the temperature as well as
electrical field stress exists [1,2,3]. Furthermore, a dependency of the material’s breakdown field strength on the temperature is
known [4]. Ongoing investigations focus
on the dependencies between conductivity,
breakdown field strength, temperature and
material’s field stress.
The Behavior of Syntactic Foam under Electrical DC Field Stress
25
Fig. 1: Syntactic foam of epoxy resin and HMS
of glass
Theoretical Basics
Whereas an ideal insulation material features theoretically zero conductivty, inside
the real insulation material charge carrier
transport occurs if the material is stressed
with an electrical field [1]. Hence, the real
insulation material features a very low conductivity, which can be described by [2]:
X
κ=
(qi ni bi )
n = Charge carrier density
q = Charge
b = Charge carrier mobility
26
Assuming that the charge q is constant,
the conductivity depends on the charge carrier density n as well as the charge carrier mobility b. The following dependency
is known for certain temperature and field
stress ranges, according to the Van’t Hoff
law [2]:
ature as well as the field stress is known [5,
1]:
κ(T, E) = κ0 · eαT · eβE
Typical coefficients for polymers are [6]: α
in the range of 0,074 - 0,114 K−1 and β in
the range of 0,018 - 0,128 mm / kV.
n · b ∼ exp(−F/kT )
k = Boltzmann constant
F = Thermic activation energy
T = Temperature
Thus, the correlation between the term n · b
and the temperature can directly be measured. Beside the temperature, the field
stress inside the material also influences the
mobility as well as the density of the free
charge carrier. This can be ascribed to the
so-called Schottky effect, that describes the
reduction of the thermic activation energy
F to Fef f by the increase of the electrical
field E [2]:
s
e3 E
Fef f = F −
4πǫ0 ǫr
e = Elementary charge
ǫ0 = Dielectric permittivity of vacuum
ǫr = Dielectric permittivity of the insulation
material
At a constant ambient temperature T the
number of free, for the charge carrier transport available electrons increases. Furthermore, the electrical field stress of the material results in a higher charge carrier mobility. Hence, the density n as well as the
mobility b of the free electrons increases.
According to the equation for the conductivity κ, a higher field stress E results in
a higher conductivity. Thus, for a certain
temperature and field stress range, the following dependency between the electrical
conductivity of a polymer and the temper-
The electrical breakdown field strength of
polymers is a function of temperature as
well [4]. Here, is has to be distinguished
between temperatures below and above the
glass transition temperature TG of the polymers. Whereas below TG the electrical
breakdown field strength decreases slowly
with the temperature, the breakdown field
strength decreases rapidly above TG .
Material Production and Object Geometry
In the present investigations a hot curing
epoxy resin system with a glass transition
temperature of 130-140 °C is used as matrix
material. The epoxy resin is filled with hollow microspheres of glass by 55 Vol.%. The
mean diameter of the microspheres ranges
below 100 µm. For the conductivity measurements, plate specimens with a thickness
of 3 mm are used. For the breakdown tests
specimens with embedded spherical electrodes of 12 mm diamter and 3 mm distance
are produced. To determine the breakdown
field strength of the material at glass transition temperature, a different epoxy resin
system with a lower glass transition temperature of 100-110 °C is used.
Test Setup and Procedure
The test setup of the conductivity measurements is built up according to DIN VDE
0303-30 (Fig. 2).
A protective ring electrode configuration is
used to seperate the volume and the surface current. A high voltage dc generator
with a maximum output voltage of 100 kV
provides the required dc voltage. To investigate the conductivity as a function of
temperature, the whole test setup is placed
in a climate chamber. To determine the dependency on the electrical field stress, the
specimens are stressed with high voltages
up to 50 kV. The temperature during the
measurements is 20 °C. To investigate the
dependency on the temperature stress, the
temperature inside the climate chamber is
varied between 20 °C and 100 °C. For this
test the voltage level is 1 kV.
The test setup for the breakdown investigations of syntactic foam under dc field
stress is built up according to DIN VDE
0303-21 und 0303-22. The specimens are
placed in transformer oil to avoid surface
discharges. The transformer oil along with
a heater pump are also used to heat the specimens to the required test temperatue. The
specimens are stressed in a voltage step test.
The test starts at 30 kV and the voltage is increased stepwise for 5 kV every 2 min until
breakdown occurs.
Experimental Results
Fig. 3 shows the dependency of the electrical conductivity on the electrical field stress
in the material.
Fig. 3: Dependency between conductivity and
field stress
Fig. 2: Test setup according to DIN VDE 030330
The meausured curve features an exponential increase of the conductivity with higher
field stresses. This effect correlates with
the theoretical basics of polymers. Hence,
it can be ascertained that also for syntactic foam a correlation between the electrical
field stress and the conductivity exists.
27
Fig. 4: Dependency of conductivity on temperature
Fig. 4 shows the dependency of the electrical conductivity on the temperature. In
analogy to the conductivity measurements
for different electrical field stresses, an exponential increase of the electrical conductivity can be observed.
28
References
[1] Bärsch, Kindersberger: Nichtlineare dielektrische Funktionseigenschaften von Dielektrika, ETGFachbericht 110. VDE Verlag.
[2] Beyer, Boeck, Möller, Zaengl:
Hochspannungstechnik,
Springer
Verlag, 1986.
Fig. 5: Dependency of breakdown field strength
on temperature
The results of the breakdown tests are given
in Fig. 5. The values are given as mean
values with 95 % confidence intervals. Up
to a temperature of 85 °C the breakdown
voltage increases with higher temperatures.
The effect can be ascribed to the internal
field distribution in syntactic foam. For
higher temperatures the conductivity of the
epoxy resin matrix between two adjacent
microspheres increases and leads to a more
homogeneous field distribution [6]. For
temperatures above 85 °C a decrease of
the breakdown voltage can be observed.
This complies with the theorie of decreasing breakdown field strength of polymers at
temperatures above TG .
Conclusion and Outlook
In the present investigations a correlation
between electrical conductivity and temperature as well as electrical field stress can
be observed for syntactic foam. The conductivity of syntactic foam increases exponentially with ambient temperature and
field stress. Furthermore, the results show
that the breakdown voltage under dc stress
depends on the temperature. For the use
of syntactic foam as insulation material in
high voltage equipment the correlations observed in the present investigations have to
be considered.
[3] Huber, Weddingen: Epoxy casting
resins with improved electrical conductivity, Colloid & Polymer Sci.
259, pp.852-858, 1981.
[4] Artbauer: Elektrische Festigkeit von
Polymeren, Kolloid-Zeitschrift und
Zeitschrift für Polymere, Band 202,
Heft 1, pp.15-25, 1964.
[5] Hampton, Chang, Hobdell: What
happens to materials under HVDC?,
CIGRÉ Session 2000, P2-001.
[6] Strauchs, Mashkin:
Impact of
Temperature and Electrical Field
Strength on the Conductivity and
Breakdown Field Strength of Syntactic, ETG-Fachbericht 125. VDE
Verlag.
Contact
Dipl.-Ing. Anja Strauchs
[email protected]
+49 241 80-94920
M.Sc. Andrey Mashkin
[email protected]
+49 241 80-94939
After the discovery of superconductivity in 1911 the transmission of electrical power seamed
to be possible. Since 1986 ceramics are investigated, which become superconductive at
comparatively higher temperatures. Using liquid nitrogen (LN2 ) whith a boiling point at
T = 77 K for cooling instead of liquid helium the operating costs of superonducting utilities
can be reduced. Thus an economical operation is possible. For insulating the nominal
voltage against ground potential, a syntactic foam consiting of a polymer, which is filled
with microspheres, is to be applied. Exemplarily a superconducting power cable will be
illustrated.
Introduction
Prototypes of superconducting power
cables mainly have two different designs,
firstly the warm dielectric
(WD) and secondly the other is
the cold dielectric (CD) design [1].
cable is interchanged (Fig. 2). Inthere the
inner conductor is electrically insulated at
first befor a vacuum insulates thermally. In
this case the electrical insulation is cold and
consists of polypropylene laminated paper
(PPLP), which is impregnated with LN2 .
For this reason it it even possible to modify
the CD cable design by making the inner
conductor massively and cooling the superconductor through the electrical insulation.
Syntactic Foam in Superconducting Cables
29
Fig. 1: Schematical layout of a WD cable
Both designs are based on a hollow copper conductor taped with superconductor
material. The hollow conductor is passed
through by LN2 . Thereby the conductor is
cooled down to temperatures of about 70 K
[2]. The difference between the WD cable
and the CD cable lies in their construction
of thermal and electrical insulation. The
WD cabel insulates the cooled down inner conductor thermally at first by vacuum.
Thus the following electrical insulation has
ambient temperature and conventional insulation materials as crosslinked polyethylene can be used (Fig. 1). The order of
thermal and electrical insulation in a CD
Fig. 2: Schematical layout of a CD cable
Due to the fact that the delivery of the cable is only performed in warm status, the
LN2 of before routine tested cables has to
be removed. Hence the routine test results
loose their significance. After installing the
cable it will be filled with LN2 again, but
thereby a new untested insulation will be
created. To prevent this effect a solid insulation system should be applied. That
would mean, that in spite of LN2 dumping
for the purpose of delivery, rotine test results keep their significance. The task of a
solid insulation system schould be fulfiled
by a syntactic foam, which is presented in
the following.
Syntactic Foam
Syntactic foam is a composite of polymer with enbedded hollow microsphers.
The microspheres have diameters of several 10 µm.
The expression syntactic
foam is derived from the foamy microscopic structure of the material. Fig. 3
shows a micrograph of syntactic foam
took by a scanning electron microscope.
This foam consists of glass hollow microsphers (1) enbedded in epoxy resin (2).
spheres, matrix material or filling degree.
3. The lower permittivity of syntactic
foam leads to an decrease of the cable capacity and thus results in a less
reactive power demand.
4. Based on the cheaper microsphers
compared to the matrix material the
material costs of the insulation system decrease.
5. The density of the insulation system
is reduced by the considerable lower
sphere density. Hence the cable is
much lighter and e.g. transport costs
can be saved.
Requirements for the syntactic foam
30
Fig. 3: Micrograph of syntactic foam
By variation of different production and
material parameters like type of spheres,
wall sickness of the spheres, matrix material or filling degree various material properties can be specifically changed. For example the material density depends on the
filling degree or the mechanical strength on
the size of the microspheres. There are
some advantages in using syntactic foam in
superconducting power cables as solid insulation over pure polymers:
1. The shrinkage of the foam by cooling down is lower compared to pure
material.
2. A specific change of material properties can be done by variation of production and material parameters like
type of spheres, wall sickness of the
The main issure of the syntactic foam is to
insulate the high voltage potential of the inner conductor of the cable agianst ground
potential. Therefore it must have a sufficent
breakdown strength. Furthermore the relative permittivity εr as well as the loss factor tan δ should be as low as possible. This
would entail less charge energy in case of
DC voltage and less losses in case od AC
voltage. The losses within the cable occur
in form of heat and leads to a raise up of
cooling complexity. Because of low efficient refrigerators the total losses increase.
Hence a low electrical conductivity of the
insulation system is recommended.
Is the syntactic foam applied in a power
cable it is exposed, in addition to electrical stresses during operation, to mechanical stresses as well. The cable is fureld on
a reel so the dielectricum has to be flexible
enough to stay proper after fureling. Nevertheless, it has to be rugged enough to hold
the inner conductor in the cable center. For
commissioning it is nesserary to cool the
cable down to liquid nitrogen temperature.
Thus, with a shrinking of the syntactic foam
is to reckoned.
First results
Measurements of the breakdown field
strength of syntactic foams in quasi
homogenious
field
(sphere-spherearrangement, sparking distance 2 mm) are
performed at room temperature and 77 K.
For these tests epoxy is used as matrix material and hollow microsphers made of glass
with a mean diameters of 40 µm are used
as fillers with filling degrees of 30 vol.-%
and 50 vol.-%. The results, presented in
fig. 4, show no significant influence of temperature on the breakdown field strength.
More measurements of the breakdown field
strength of further syntactic foam compositions will be performed to get the impact of
temperature on the breakdown behaviour of
syntactic foam.
References
[1] A. Bulinski, J. Densley, High Voltage Insulation for Power Cables Utilizing High Temperature Superconducticitiy, IEEE International Conference on Conduction and Breakdown in Solid Dielectrics, 1998.
Finaly, due to the cables low operation temperature, the syntactic foam needs certain
thermal properties. In the modified CD
cable design the superconductor is cooled
through the electrical insulation system.
Hence, to cool down the superconductor
by commissioning and to hold the superconductor temperatur under his transition
temperature during operation the syntactic
foam must have a sufficent thermal conductivitiy. As well as in AC application the heat
losses during DC caused by harmonics are
in the range of 1 W/m [3], which has to be
dissipate through the syntactic foam.
[2] C. Matheus,
Technische und
wirtschaftliche Einsatzmöglichkeiten
supraleitender Energiekabel, Dissertation RWTH Aachen, 2005.
[3] R. Bach, W. Prusseit, Supraleitung
in EVU-Netzen - Konzept für eine effiziente Energieversorgung von Ballungsräumen, EW Medien und Kongresse GmbH, 2009.
31
Contact
Dipl.-Ing. Daniel Winkel
[email protected]
+49 241 80-93033
Fig. 4: Breakdowm field strength and confidence intervalls of two syntactic foams
at different temperatures
Generation of Synthetic Low and Medium
Voltage Grid Models
As a consequence of a rising number of decentralized generation as well as electric vehicles,
there are new challenges to planning and operation of electric distribution grids. In order
to make generally accepted predictions about the necessity of grid reinforcement and the
amount of money that needs to be invested, representative grid data is required as a basis
for calculations. In the following, different approaches will be presented that enable for
a generation of grid models that are equal to the entirety of German distribution grids in
terms of their electrical and topographical characteristics.
Introduction and Objective
32
Several studies at the Institute for High
Voltage Technology analyse the integration
of electric mobility and renewables into the
distribution grids at medium and low voltage levels. Different data sets for both voltage levels are publicly available - statistical data about grid assets and topologies
for LV level and coordinates of substations
for MV level - and can be used in two
different approaches to create grid models,
which will be described in the following
sections. However, a combination of the
grid models created with either one of both
approaches is possible and allows for an integrated study of operation principles looking at both voltage levels at the same time.
Additionally, a combination of synthetic LV
grid models with real MV grid data is possible and allows for an assessment where
electrical grid data is only available for MV
level. Synthetic grid models in this context
are defined as data sets, that can be used for
load flow study like data from real grids, but
that are artificially generated.
Composition of Low Voltage
Grid Models
An assessment of the integration of new
technologies into distribution grids cannot
be done only by taking rated power and
a coincidence factor into account. Moreover, predictions about average and maximum load on transformers and cables as
well as voltages along lines can only be
achieved by load flow calculations, because
of the rising complexity and the increasing
number of possible operating conditions.
As a sufficient amount of grid data that
is required for this kind of studies is not
available, synthetic grid models have to be
developed. The required statistical information is available from [1], [2] and [3].
Data sets that are required for the synthesis of grid models and that are used in the
approach developed at IFHT are shown in
the following list. A classification of different grids and a connection with medium
voltage grids can be done according to
different types of settlements. The data
considered within this approach includes
amongst others length of lines, branching
of lines, types and their cross sections, the
number of households and their respective
transormer rating. Besides, the distance
between houses, number of housholds per
house and the building type have been taken
into consideration. The information about
buildings is also used in order to identify
the possible size of decentralized generation plants, taking the size of roofs (for PV
installation) and the heat demand of differ-
Field of Research: Sustainable Energy Systems
In order to provide region specific conclusions their inherent and mainly historically
driven topology and electrical grid characteristics must be taken into account. For this
purpose a distinction between rural, urban
and suburban area has been made, which
is incorporated into a two stage model
for generation of synthetic medium voltage
grids. This model considers a scatter plot of
distribution grid stations and a transformer
station respectively in order to approximate
a realistic medium voltage grid based on
the data given. The scatter plot is based on
freely available geo referenced local transformer stations. The first step only approximates possible groups of transformer
stations, which identify possible topological structures such as ring or mesh solutions. Based on the statistical results related to topological and electrical properties
of real medium voltage grids (see above) a
travelling salesman approach is utilized to
connect different local transformer stations
according to the possibly shortest path.
An exemplary result is shown in figure 1
comparing the generated grid (highlighted
in black) with the original (highlighted in
grey).
Topological generation of synthetic medium voltage distribution grid structures
The approach illustrated within this chapter
generates synthetic medium voltage grids,
which enables very general conclusions compared to the approach mentioned above
- related to integration potential of decentralized resources. Based on an analysis
of electrical and topological properties of
available real medium voltage grids first
general conclusions related to topological
and the respective electrical properties have
been drawn. The main data, which was
analysed include population density, number of local networks stations, length of ring
topology, cable length and the category of
regions mentioned below.
ent types of houses into account.
A synthesis of grid models is carried out
based on the probability distribution functions of this data and offers the advantage
that an infinite number of different grids
can be created. Therefore, also grid models with rather extreme values of parameters can be used for evaluation. Acquiring
an equal amount of data about real grids
and converting it for load flow calculations
would require much more effort. Moreover,
data sets of the low voltage level that can be
used for load flow calculations are quite often not even available from grid operators.
The algorithm to create synthetic grid models works based on statistical data of today’s
distribution grids. This means that it is not
be mistaken for an algorithm for grid planning based on information about the load to
be supplied. Therefore, grid structures that
have evolved over long periods of time are
implicitly represented. Hence, challenges
to distribution grids and required measures
for reinforcement can accurately be calculated.
33
References
[1] Jörg Scheffler, Bestimmung der
maximal zulässigen Netzanschlussleistung
photovoltaischer
Energiewandlungsanlagen in Wohnsiedlungsgebieten Dissertation an
der TU Chemnitz, Chemnitz, 2002
[2] Georg Kerber, Statistische Analyse von NS-Verteilungsnetzen und
Modellierung von Referenznetzen
http://www.hsa.ei.tum.de/
Publikationen/2008/_Kerber
Witzmann_Energiewirtschaft_32008.pdf
Seitenabruf: 15.05.2009
Abb. 1: comparison of real grid (black) and
generated grid (grey)
34
The second step converts the heuristically
generated solution into a cost pattern indicating the minimal expenses necessary related to installation and material cost. Besides, regional aspects such as course of
the roads or forests etc. are taken into account, which impact possible routes for cabling significantly. Depending on the regional details taken into account this solution might already present a pretty good
approximation, which is then benchmarked
with a real grid topology. The two stage approach enables generation of a large number of medium voltage grids, which follow
real grid data. If generating a large number of medium voltage grids general conclusions related to integration possibilities
of decentralized generation becomes possible.
[3] Georg
Kerber,
Belastungsfähigkeit
von
Niederspannungsnetzen bei PV-Einspeisung
http://www.energieagentur.nrw.de/
files/Belastungsfähigkeit
von
Niederspannungsnetzen.pdf
Seitenabruf: 11.09.2009
Contact
Dipl.-Ing. Claas Matrose
[email protected]
+49 241 80-94912
Philipp Erlinghagen, B. Sc.
[email protected]
Thomas Pollok, M. Sc.
[email protected]
+49 241 80-94958
In many countries a strong transformation regarding the generation pattern of electrical
energy is taking place leading to distributed and volatile energy conversion systems. In
Germany for example, it is planned to build 25GW offshore wind turbines until 2030. This
transformation of generation structures and the continued expansion of cross-border electricity trade are placing new demands on the transmission networks, making measures to
increase the transmission capacity necessary. At the Institute for High Voltage Technology,
long-term strategies such as expansion measures for the electrical infrastructure and the
necessary boundary conditions are analyzed and discussed.
Due to the current changes in the electrical
energy supply, transmission networks are
facing new challenges. Today’s transmission systems were built and designed for a
centralised generation close to load hotspots. In many countries however, a transformation of generation structures, particularly towards renewable energy sources, is
taking place. The renewable energy sources
are usually decentralized, volatile and located far from load hotspots. Also, there are
additional factors such as the expansion of
international trade in electricity. These developments will set up new demands on the
electrical transmission networks. Network
congestion will thus constitute a major barrier for a further integration of electrical
energy supply on a renewable basis. In particular, Germany with its strong promotion
of renewable energy sources is facing these
problems.
EU network model
To enable the integration of electrical energy from renewable sources into the transmission system, an expansion of the network will be inevitable. An analysis of
the necessary expansions requires an exact
knowledge about the structure of the network, load and production patterns as well
as their change.
For such considerations a model of the European electrical transmission network was
developed at the Institute for High Voltage Technology which also contains load
and generation patterns in a high geographical resolution. The model contains several
thousand nodes, lines and transformers and
more than 2500 generation units (see Figure 1). All network nodes and generation
units are geographically referenced so that
the effects of local changes in generation
can be mapped to the transmission network.
The power generation structure is modeled by means of various pan-European databases, again including detailed information
about the locations of the power plants.
For the mapping of the temporal change in
generation patterns different scenarios for
the country-based evolution of these patterns are introduced. The scenarios specify
the development of the installed capacity
for each country and each type of power
plant. With the knowledge about planned
power plant projects and the age structure
of the existing power plants, it is possible to
obtain a spatial information about the development of the European generation structure. Thus, an estimation about the location
of new power plants and their properties can
be made, including an estimation where old
generation infrastructure will be shut down.
Model of the european transmission grid for
the assessment of expansion measures
35
Fig. 1: Model of the transmission grid, utilisations according to OPF in case of high load and strong
wind
36
Fig. 2: Installed generation capacity of wind
power plants in 2030
The elements of the adapted power plant
databases are then assigned as generators to
the nodes of the network model, which is
made possible due to the geographical informations contained in the models.
The load and the installed capacity of wind
power plants and photovoltaics can be resolved in node-based data using various
methods. As an example, the projected installed generation capacity of wind power
plants allocated to the network nodes in
2030 is shown in Figure 2. The striking
peaks at the German North Sea coast result from offshore projects. By combining
the models a simplified model of the entire European electricity supply is created.
To simulate this model, various methods
are used, including Power Flow Calculation
(PF), Optimal Power Flow (OPF) or Security Constrained OPF (SCOPF). Depending
on the application, the objective function
and the constraints of the formalisms can be
formulated in a problem-specific way. For
example, a cost or emission minimum can
be found, in compliance with network restrictions. Despite the large number of parameters and variables, a full OPF including
the consideration of reactive power and losses (AC-OPF) for the respective model can
be computed for a single point in time sufficiently fast to enable the use in scenario
analysis methodologies, Monte Carlo simulations etc.
Network extension measures
Using geographical references makes it
possible to simulate proposed network expansion measures and their infrastructural
impact. For an economic assessment of these measures the generation cost are considered which are determined via an OPF.
If the expansion measure removes weak
network points it is directly reflected in a
noticeable cost reduction. A technical assessment can be conducted for instance by
simulating the reduction effect of a specific
expansion measure on the network stress in
case of an asset outage, the so called (n−1)situation. For an ecological assessment the
CO2 -emissions resulting from a cost driven
OPF are considered. This approach can be
sophisticated by using a simplified Ecological Optimal Power Flow which is able to
reveal expansion measures that are economically, but not ecologically effective and
vice versa.
At the Institute for High Voltage Technology the European network model and the
methodology for the assessment of future
expansion measures are constantly refined.
For the purpose of highly detailed analyses,
the assessment of the European transmission network is expanded by also considering
the underlying network levels. Furthermore, the networks of the Scandinavian countries, the United Kingdom and Ireland have been added to the model of continental
Europe. This enables the simulation of future large scale projects such as the “North
Sea Grid“ which has been proposed by the
European Commission and is intended to
connect the offshore wind farms with the
respective European neighboring countries.
Furthermore, also the modeling and the associated assessment of the competing technologies for these kinds of projects, such as
hybrid networks, flexible AC transmission
systems (FACTS) and meshed high voltage
DC networks (meshed HVDC), are subject
to the current and future research at the Institute for High Voltage Technology.
Summary
In order to facilitate the integration of
power generation based on renewable energy sources into the European network the
Institute for High Voltage Technology uses
its existing models which are constantly refined to assess different network capacity
enhancement strategies. As long-term solutions, network expansion measures, in particular of the European transmission network, are investigated and assessed using
high detail models developed at the Institute for High Voltage Technology.
Acknowledgement
The network model was developed for
the EU-FP7 project IRENE-40 (www.irene40.eu).
Contact
Dipl.-Ing. Hendrik Natemeyer
[email protected]
+49 241 80-94913
Dipl.-Ing. Sebastian Winter
[email protected]
+49 241 80-94914
Dipl.-Ing. Martin Scheufen
[email protected]
+49 241 80-94941
In order to model different states of the
power transmission network, different scenarios are defined which are suited to illustrate the varying conditions of the network.
They are designed to simulate different load
patterns as well as the fluctuating availability of renewable energy sources by considering also local power peaks for instance due
to strong wind conditions in the North Sea.
37
38
Optimisation of the operation of integrated
supply systems for electricity and heat
Based on a simulation model for the analysis of heat pumps and dispersed units for combined heat and power generation a tool has been designed which calculates the optimal
operation strategies for these units by applying generation and load management. At the
same time the influence of the addition of electrical and thermal storage systems on distribution networks is analysed using different objective functions.
Introduction
A strong decentralization of energy supply is expected to occur in Germany in the
course of the coming years. As a result of a
growing share of renewable energy sources
with their inherent volatility and uncontrollability of generation, action is needed in
order to balance the influence of fluctuating renewable energy sources and to ensure
an uninterrupted power supply. The integration of energy storage systems into the
existing electricity networks is an important
component in order to realize the projected
expansion of renewable energy sources and
at the same time ensuring security of supply. The use of thermal energy storages offers the possibility to adjust the operation
of heat pumps and cogeneration units to the
electricity demand in the network without
endangering the securing of the heat supply.
Modeling of Plants
The decentralized conversion technologies
are mainly connected close to the loads in
the respective distribution networks at a low
voltage level and are usually operated independently (from each other). Systems
of combined heat and power (CHP) work
mostly in heat driven mode, which means
that their operation depends on the local
heat demand. To investigate the influence
of increasing decentralized energy production in the existing networks and in order to
perform an economic and ecological analysis, a bottom-up modeling approach of the
various decentralized conversion technologies to account for the stochastic operating
behavior has been implemented in MATLAB [1]. Furthermore, the use of thermal
and electrical storage technologies in intelligent distribution networks is examined
under different operating strategies. The
technologies considered are combined heat
and power plants, heat pumps and, additionally for each facility, a thermal tank to
avoid the undesirable clock-operation of the
systems. In addition, stochastic generation
profiles for photovoltaic and small wind turbine generators based on historic time series data are used.
Exemplarily the approach for CHP units is
described. The rated power of the cogeneration facility is set in the model to a reasonable level with respect to the heat demand in the building assuming dual-mode
operation. In addition, a peak load boiler is
included for each plant to support CHP on
the coldest days of the year. As input parameters the model uses a heat load profile.
Depending on building type, year of construction and rehabilitation a practical supplement is added [2]. Each CHP plant is either turned on or turned off at each time interval of the day according to the local heat
demand and the condition of the existing
thermal storage. Since the state of the thermal storage and heating demands of the individual objects differ from each other, the
output of the model comprises a stochastic
production profile for each day of the year.
In Fig. 1, for example, the production pro-
20
15
15
10
10
5
5
0
0
2
4
6
8
10
12
14
16
18
20
22
0
24
Fig. 1: Synthetic production profile for CHP
(example)
Storage systems
Optimisation of the operation
The modelled generation profiles represent
the heat driven operation of CHP units.
Consequently the operation hours depend
on the demand of thermal energy by the
object to be supplied.
In this operation mode, the generated electricity is fed
into the distribution network without taking the current demand for electricity into
account. Combined with additional local
electricity generation (e.g. from photovoltaic) a situation might occur in which
the surplus of energy endangers the stable operation of the electric power grid.
30
Balance of electrical power
generation of heat
thermal power [kW]
electrical power [kW]
generation of electricity
20
of their placement from exogenous influences.
file (electricity and heat) of a cogeneration
plant for a house on a winter day is presented. It shall be noted that the profiles
for each household are generated individually so that the entirety of units is modelled
accurately.
20
A range of technologies is able to store thermal energy. However using today’s knowledge only systems based on sensible heat
storage1 are economically feasible. At temperatures which are typical for domestic
heating the typical technical solution would
be an insulated water reservoir. Compared
to other materials such as concrete or sand
the high thermal capacity of water (1.17
Wh/(kg*K)) leads to a sufficiently compact
design. Latent heat storage systems using
phase change materials or systems based
on reversible chemical processes are not included in the model because of their high
costs and limited availability on the market.
However, they can be easily added to the
model by using new parameters for costs
and losses. For storing electrical energy the
assessment was limited to different types
of battery storages differing in investment
costs, efficiency and standby losses. With
the focus on distribution networks they can
be seen as the preferred technology because
of their flexible size and the independence
10
0
-10
0
2
4
6
8
10
12
14
16
18
20
22
-20
-30
time
Heat driven CHP operation
Generation management
Fig. 2: Intelligent operation control of CHP
units
By the introduction of thermal energy storages it is possible to shift the operating
hours of the CHP units to time intervals
with insufficient generation (see Fig. 2)
because the heat storage guarantees that
the demand of thermal energy is met at
any time. This optimisation can be carried out by using the objective of a distribution system with a high degree of autarky. This means in this case that the
distribution network is almost independent
of the transmission network and is mainly
supplied by local generation from renewable energy sources and CHP. A second ap-
1
Sensible heat storage systems directly store thermal energy by heating a storage medium like
water, stone oder salt.
39
Controllable CHP
unit in operation
Balance ofel. power
Target
Controllable CHP
unit out of operation
and demand of roughly 20%. In order to
also compare production costs of the specific technologies, life spans and costs have
been assumed according to [3]. The analysis shows that a combined operation of CHP
units and thermal storage systems within
an intelligent distribution network can provide similar levels of autarky at much lower
costs compared to the installation of battery storage. Firstly, the advantage of heat
storages rises faster with lower additional
costs. However, there is point of saturation
when additional heat storage yields no further benefits.
90%
Grade of energetic autarky
proach for the examination is the harmonisation of power flows. The objective function aims to reduce the maximum load of
the assets in order to reduce transmission
losses. Apart from the different objective
functions both approaches are based on the
implementation of a generation management for CHP units and a load management
for heat pumps, respectively. In the following the approach for CHP units is described.
Based on the temperature of the heat storage and a number of technical parameters
it is checked whether the current condition
of the CHP unit necessitates changes to the
current state of operation. Using a projection for the following 24 hours the state of
operation is analysed with a time resolution of 15 minutes. If deemed beneficial
a change in the state of operation will be
done. The constraints are shown in the simplified Fig. 3.
85%
80%
75%
70%
0
5.000
Li-Ion
40
CHP
management
Set out of operation
Minimal duration
of operation reached
Water
15.000
Annuity [€/a]
Li-Ion+Water
20.000
25.000
Lead+Water
Fig. 4: Autarky of the system using different
storage technologies
Set into operation
Thermal load
covered
Pel < required
load
Pel < required
load
10.000
Lead
New temperature
of storage
Boiler
Generation management
Fig. 3: Generation management for CHP units
The approach for heat pumps follows the
same principles while different technical
parameters have to be taken into account
and the objective of the controlling is inverted as a heat pump is an electrical load.
Exemplary results
The developed model has been used for
an exemplary supply area with 102 private
households. In the network area examined
the local electricity generation from CHP
(56%), photovoltaic (36%) and wind energy
(8%) matches approximately the annual energy demand of 300 MWh. However, there
are seasonal differences between generation
An example for the relationship between
costs and autarky is shown in Fig. 4. It
displays the results for the supply area described above using today’s costs and life
spans for battery storage systems. A scenario analysis has been carried out which
showed that for any generation mix there is
always a region in which heat storages are
superior to batteries when considering the
ratio of cost- to autarky increase. The combined operation of electrical and thermal
storage (dashed lines) allows higher grades
of autarky at lower costs compared to the
sole operation of battery storages.
Whereas the objective of autarky aims to
bring the load balance down to zero, the target value becomes variable with the objective of power flow harmonisation. For the
supply area described above a foresight on
generation and load has been done with a
resolution of 15 minutes. The mean value
energy sources and CHP a supply area can
be self-sustaining for some periods of time.
For this purpose the objective function for
load and generation management could be
changed in a way that the energy exchange
with the transmission grid becomes dependent on the electricity prices on the wholesale markets in order to generate additional
income towards the distribution grid.
References
80
60
[1] T. Smolka: Ökologisch-technische
Auswirkungen dezentraler Energieversorgungsszenarien mit Blockheizkraftwerken in elektrischen
Verteilungsnetzen;
Disseratition,
RWTH Aachen, Aachen 2008
Balance of electical power [kW]
40
20
0
-20
-40
of the load balance then is the target value
for load and generation management. This
relationship is shown in Fig. 5 for a selected week. The target value is time dependent and rose slowly during the week
from a starting point of -18 kW. As a result the analysis of the assets shows that
the loads on lines and secondary substation
transformers are significantly lower than in
the unaffected operation.
-60
-80
0
12
24
36
48
Status quo
60
72
84
96
108
120
132
144
Time [h]
Autarky (energ.)
Homogenization
156
Fig. 5: Load balance of the system in a selected
week depending on the objective function
Conclusion and outlook
In a first step the introduced method allows simulating the operating behaviour of
dispersed energy conversion units and the
influence of a significant number of these
units on the distribution networks. Second, a generation and load management has
been implemented in order to control the
load balance of the supply area according
to the chosen objective function. Therefore
the operation of thermal and electrical energy storage has been included. In the future the model shall be linked to an optimisation tool for designing the setup of the
heat and electricity supply in a specific area.
Using local generation based on renewable
[2] W. Lutsch, F. Witterhold: Perspektiven der Fernwärme und
der Kraft-Wärme-Kopplung; Arbeitsgemeinschaft für Wärme und
Heizkraftwirtschaft - AGFW e. V. ,
Frankfurt 2005
[3] U. Bünger et al.: Energiespeicher
in Stromversorgungssystemen mit
hohem Anteil erneuerbarer Energieträger; ETG Task Force Energiespeicher,
Energietechnische
Gesellschaft im VDE (ETG), Frankfurt 2009
Contact
Dipl.-Ing. Sepideh Doroudian
[email protected]
Dipl.-Ing. Stefan Krengel
[email protected]
+49 241 80-93034
41
42
Agent-based traffic models
for local emissions analysis
By using an agent-based traffic model and a separate examination of every single vehicle,
the streets capacity utilization can be determined in a very high time resolution. The previously made analyses of time-differentiated charging processes can be extended by another
spatial component. With an examination of movement patterns it is possible to get an estimation for the locally generated emissions and to analyze the spatial linkage of loading
processes of the vehicles.
Introduction
The expected strong increase of electric
mobility outlines a new challenge for grid
operators regarding reliable and safe operation of energy supply networks. An integrated model of electricity networks and
transportation networks gives the opportunity to analyze the impacts on power supply caused by a comprehensive integration
of electric vehicles considering both energy
and transportation flows. Therefore, synthetical driving patterns are generated in the
beginning and are substituted by real driving patterns later on.
This was extracted in seperate layers.
(Fig. 1) shows the levels
„street network“ and „residential areas“.
Fig. 1: Street network and housing areas
Traffic model
The traffic and the road network have a
special significance in the traffic modeling.
With the knowledge of the exact position of
each vehicle, it is possible to state the availability and the potential of each vehicle and
its storage capacity in a certain region. In a
further step, the knowledge about the driving behavior is used to control charging
processes.
In order to generate schedules for the vehicles, it is necessary to know where the
drivers live, what job-related drives they do
or where they drive to for private reasons.
In addition to the street information, the
geological data that is used also contains
information about the land use.
Integrated modeling
Through a combination of both models, the
traffic network and the electricity network,
an integrated traffic and energy flow model
is realized as it is shown in (Fig. 2). Another component is a central control which
effects and controls the charging process.
The more information it receives from the
vehicles, the more effective it is.
The data about the standing times and
future driving destinations generate the
biggest benefits. The vehicle must be informed by the driver with these data, e.g.
through a modified gps-system, so that the
charging processes during the parking time
can be controlled optimally in time and
space.
Fig. 2: Integrated simulation model
Results of the integrated modeling
The impacts of an uncontrolled charging
behavior of the vehicle population on the
electricity network was analyzed. Therefore three scenarios for the availability of
charging infrastructure, „everywhere“, „at
home“ or „at home and at work“ were
considered. The increase of the overall
load caused by electric vehicles in a certain region is illustrated in (Fig. 3). The
considered rural region has a size of approximately 2000 km2 with 290.000 inhabitants and 150.000 automobiles of which
30% are assumed to drive electrically. The
peak load is 360 MW. It has to be noticed, that in consideration of a single day
only 65% of the electric vehicles actually drive. The rest is parked and connected to the grid in a best case scenario.
Fig. 3: Load increase by electric vehicles
In a further step, the ecological impacts of
electronical vehicles on their environment
can be captured and a comparison to conventional automobiles can be made. In order to be able to make an appropriate comparison between electric vehicles and conventional vehicles, it is necessary to create definite, ecological critical areas, the socalled impact categories, in which the comparison should occur. Therefore categories
are considered in which a significant difference between the two types of cars is
noticeable in respect of the ecological impacts. The investigations of the fine dust is
one of the categories, because an electric
vehicle does not emit fine dust. Furthermore, an electric motor does not produce
noise or any local CO2 emissions. The addressed impact categories are therefore fine
dust, noise and CO2 emission. In order to
outline the influence of an integration of
electric vehicles in these categories, there
has to be a description of the current load
state in the considered region. Based on this
description, the influence on the regions is
shown by increasing the number of electric
vehicles.
An electric vehicle saves, compared to a
conventional vehicle, up to 70% of the
emission in the fine dust category. The remaining 30% are emitted by tire and street
abrasion and cannot be avoided by electric
vehicles. With the help of data about the
emission per automobile, statements about
the streets fine dust pollution can be made
in g/km. A conversion methode was established with real measured data. The resulting factor serves as an expected value
for statistic analyses for the probability of
a limit violation. As a result of the simulation in the fine dust category it has to be
recorded, that a low penetration rate, which
is realistic in the future, would only have a
small impact on fine dust in the annual average. A percentage of 10 % of electric vehicles would lead to a decrease of fine dust
Ecological impacts
43
pollution by 1.7 % in a strongly used street.
However, this decrease would have a substantial influence on the probability of the
limit violation. It would fall from over 60%
to under 40% in a strongly used street as it is
shown in (Fig. 4). A noticable improvement
of the quality of living is only realistic with
30% of electric vehicles on a medium term.
Fig. 4: Fine dust concentration for different
scenarios and the probability of limit violations
44
The calculation of the CO2 emission follows the same pattern. In order to calculate the load, the data about the CO2 emissions of all vehicles on the road is used.
This is based on the noise averaging level
LDEN. The calculation of each factor depends on the traffic volume and the average percentage of trucks on the road. In the
range of the local CO2 emission a tremendous relief through electric vehicles can be
expected. The road traffic noise reduces
enormously through an integration of electric vehicles mainly in housing areas. With
a percentage of 10% of electric vehicles the
load decreases about 6% in streets where
the speed limit is 30 km/h and in streets
where the speed limit is 50 km/h it only
decreases about 2%. Overall, a strong integration of electric vehicles leads to a relief regarding the considered impact categories especially in the city centers. However, with a low penetration rate the effect
is small. Therefore, electric mobility is going to improve our quality of living only on
a medium term.
Contact
Dipl.-Ing. Thomas Helmschrott
[email protected]
+49 241 80-97340
Dipl.-Wirt.-Ing. Eva Szczechowicz
[email protected]
+49 241 80-94916
Field of Research: Systems Engineering and Asset Management
The reliable estimation of quantity structures of the equipment within electrical transmission systems represents a challenge all over the world due to insufficient and inconsistent
public data. The results of such assessments, particularly of expensive equipment such as
power transformers, are part of the decision-making in the context of business activities
in the energy sector. The presented method of synthetic mesh generation enables calculatign a network for a country on the from scratch, which fulfills the supply task, whereas
the procedure itself is based on publicly available information and technical, economic and
geographical conditions. The resulting synthetic network enables the approximation of the
quantity structures of expensive equipment in the actual electrical transmission system of a
country.
Introduction
There is no global data base available to
determine the installed quantity structures
of equipment in electrical transmission systems of individual countries or regions. In
European countries, there is only information on the number and cumulated capacity
of power transformers available as well as
of route lengths available. These are subject
to the inconsistent and sometimes incomplete inquiry. The exact knowledge of the
actual equipment quantity is an important
basis for economic and strategic decisions
such as the buying of power systems, infrastructure investment, opening new markets
for products and services as well as the assessment of the own market position.
Especially in countries with poor public data like emerging markets, an option to estimate the quantity structures is quite important.
A preliminary approach for the derivation of a transferable regression model for
the number and capacity of power transformers on the one hand confirmed the presumed correlation with selected input data,
on the other hand showed high divergences
when transferred to countries - especially
non-European ones - outside the dataset for
parametrization. A significant influence of
parameters not regarded due to a lack of
availability and of operator-specific philosophies is likely to be responsible.
For the synthetic mesh generation, the historical developments are considered to be
not reconstructable. Therefore, geographical boundary conditions and the spatial distribution of loads and generation are of relevance. Based on current input data, a minimal reference network is developed which
can fulfill the supply task of the transmission network. Precondition for the application is a centralized production structure by
large-scale power plants in the investigated
countries. Results of the process are the network topology and the quantity structure of
costly equipment in a synthetic network.
Analysis of available input data
Cumulative data with a national focus is
collected worldwide but the range of variables, criteria for the collection and spatial
resolution differ greatly between the gathering competent authorities. Thus, collection and standardization of data on quantity
structures of equipment out of individual,
scattered sources is impossible for a global
data base with data such as
• installed generation capacity
Synthetic generation of network topologies
using publicly available data
45
46
• anually generated, imported and exported electric energy
• annual energy consumption and losses
• total population
• degree of electrification
In contrast, geo-referenced data assign geographic points or areas to properties. Properties of surfaces are then present in the
form of raster data. Geo-referenced data about generation sites is also available
worldwide or can be obtained by a proven
systematic approach with calculable effort.
The initial degree of the coverage of centralized generation compared to the cumulative variables is usually over 70%. Geographical information such as the discrimination between land and water areas, elevation
profiles etc. are available for all countries
worldwide.
Globally available geo-referenced data
related to load balancing, which are used as
the basis for the estimation:
• population density
Fig. 1: Flowchart of the process
To determine the load, a correlation between the distribution of electrical load and
the population on the national territory is
adopted. Basis of this assumption is the mutually dependent position of focal points of
population and economic sectors. In figure
2, the determined load map for the Netherlands is shown.
• land use
• electric night lights
• degree of electrification (restricted)
The further, combined processing of these
different types of input data is shown in the
next section.
Procedures and results of a typical
application
The process of synthetic mesh generation creates a technically acceptable, reliable and economic electric transmission network. The process follows the steps shown
in figure 1. There are several variants of
a technically acceptable system generated,
whereas the most economical result is finally selected. The steps are outlined below.
Fig. 2: Identified load distribution
The algorithm to generate the supply areas
of the distribution network level (including
the high voltage level) uses the determined
Discussion and outlook
The method shown by the example of the
Netherlands identifies a circuit length for
the transmission network of approximately 90% and a number of transformer of approximately 92% of the real values. Crossborder interconnections and different high
voltage levels are currently not taken into
account.
In contrast to purely statistical methods, the
synthetic mesh generation is able to consider both the geography of a country as well
as structural information such as the distribution of the population. The generated
electrical power is also based on technical
and economic conditions to ensure the best
possible representation of reality, with the
aim to approximate the quantity structure of
expensive equipment for as many countries
as possible.
Due to the „green field“ approach of the
economic optimization of an electrical network by planning from scratch, without taking historical data into account, the synthetic mesh generation additionally shows
potential concerning the generation of optimal reference- or target networks for the
current supply task.
Kontakt
Dipl.-Ing. Christian Hille
[email protected]
+49 241 80-94915
[email protected]
+49 241 80-90015
Fig. 3: Synthetically generated network with
supply areas including substations and
power plants
load map. Each of these supply areas includes, as a black box without detailed structural mapping, the load of a calculated portion
of the geographic land area up to a certain
limit. In all cases, a substation is used as a
central anchor point between the transmission and distribution network level.
All of the substations, along with the production sites, form the nodes that need to
be connected by the transmission system.
Both the rating of power transformers and
the interpretation of the electric circuits of
the transmission system are designed for a
reliable supply. An overloading in the maximum load case and the failure of equipment
or a circuit is avoided by an appropriate design and redundancies.
From all generated power variants, the costoptimal synthetic network is identified as a
result of the procedure by comparing the
profitability. The economic evaluation includes annual pay ranges out of operating
costs and the annual investment costs of the
equipment. Fig. 3 shows such a synthetic
system for the Netherlands. Displayed are
the supply areas, the transmission grid and
the production sites. Their level of performance is expressed by the diameter of the
corresponding circular areas.
47
48
Challenges for protection systems in distribution grids with significant dispersed generation
High future penetration levels of decentralized generators and storage devices will potentially endanger the functionality and selectivity of traditional protection systems in electrical
distribution systems. The broad range of deciding factors prevents up to now an efficient
assessment of the threat potential and an objective decision on necessary remedies. This
article gives an overview on the influencing factors, shows some example protection threats
and sharpens the questions to be answered.
Protection in distribution systems
Selective protection of low voltage (LV)
and medium voltage (MV) distribution systems is mainly achieved by non-directional
overcurrent protection devices. Examples
of such are:
• fuses (LV+MV)
• LV line switches for homeinstallation
• overcurrent-relais + circuit breakers
Successful usage and rating of those protective devices depend on several assumptions.
Firstly, one assumes a mono-directional
power-flow to the periphery of the distribution system in normal and in faulted operation. Secondly, a significantly differing current level between those states are assumed.
In the absence of decentralized generators
and storage devices the mentioned protective devices are a robust, economic and fieldtested solution for ensuring an adequately
protected operation of distribution systems.
Scenarios of distribution system developments
The growing integration of decentralized
generators (e.g. photovoltaics, combined
heat and power plants, small wind turbines
and run-of-river power stations) and of bidirectional storage devices (e.g. electric vehicles) - in the following summed up as “decentralized infeed” - will constantly or from
time to time violate the validity of the named assumptions.
Besides this fundamental change of the current flows in distribution systems experts
discuss and predict a change of the grid
itself. Migration from radial feeder operation to closed rings or even meshed structures may improve voltage maintenance and
minimize influences of decentralized infeed
on power quality.
Experts consider an increase of controllable components and sensors necessary. Sectioning points, loads, generators and storage devices shall be (remotely) controllable. For this purpose one needs an extensive
amount of automation and communication
technologies. Smart meters may become a
way to extend the existing minimal amount
of sensors drastically.
The sum of these developments aims towards an active control in distribution systems’ operation. The latter shall enable an
optimal utilisation ratio of the equipment
and an efficient use of electrical energy. To
ensure a high reliability of supply temporary islanded operation is suggested to avoid
supply interruptions in case of blackouts of
the upstream grid.
The changes depicted by these scenarios
need huge investments by distribution system operators in order to build up the necessary infrastructure. Huge circuit lengths
and huge component numbers lead to the
assumption, that a gradual change will rather take place in existing distribution systems than a sudden change over all systems. Thus, classical and new active distribution systems will prospectively coexist
for a long time.
Scenarios of decentralized infeed behaviour
Due to the change of the distribution systems’ structure and components a development of the requirements towards decentralized infeed is expected and needed.
Sources connected to the low voltage grid
shall nowadays disconnect from the grid rapidly in case of a power system fault or in
case of unintentional islanding. This passivation of the grid is among other things intended to reestablish the conditions that were assumed when designing and dimensioning the traditional protection system. Today, distributed generators connected to the
medium voltage network are already required to be able to supply ancillary services.
Due to the increasing penetration of lowvoltage distribution systems with decentralized generators and storage devices (e.g.
electric vehicles) we expect an extension
of this requirement to low-voltage infeed.
In this case, the now favored passivation
is no longer applicable to preserve traditional protection system functionality. In dis-
tribution systems with local high penetrations of decentralized infeed might apply
the Microgrid-concept in the future, part of
which is a connection to the overlying network with lower rating than necessary to
supply the installed load at once. Without
load-shedding a simultaneous disconnection of all decentralized infeeds would result
in critical overload conditions.
As long as the described infrastructure for
controlling the distribution systems is not
available comprehensively, an uncontrolled
behavior of the distributed infeed needs to
be assumed.
Threats to traditional protection systems
In case of uncontrolled decentralized infeed
we expect an influence on the functionality
of traditional protection systems. An example is an unacceptable delay of operation of
protective devices. This for instance may be
caused by blinding of feeder protection in a
situation as depicted in fig. 1. This effect
may lead to a loss of service live or destruction of the protected components and may
furthermore endanger persons or animals.
Another example is an unselective sympathetic tripping of healthy feeders in case of
a fault in neighbour-feeders as depicted in
fig. 2. Under certain conditions the protec-
Abb. 1: Blinding of feeder protection FA by Generator G. Relevant parameters for modelling according to IEC 60909
49
Abb. 2: Sympathetic tripping of feeder protection FB by fault in feeder A. Relevant parameters for
modelling according to IEC 60909
tion of feeder B will trip although the fault
itself is located in feeder A.
50
Other cases similarly lead to unnecessary
costs and service interruptions. One main
challenge of the integration of decentralized infeed is, that protection investigations
need to simultaneously consider so far independent parts of the distribution system.
One needs to consider the grid in total with
all connected components.
Even in case of a controlled operation of the
distribution system proper protection needs
to be ensured, for instance when automation or communication systems fail.
Furthermore, new system states previously
unknown will exist, which will violate completely the assumptions that originally lead
to today’s protection concepts. These system states may not be observable and will
lead to a lack of operation of the protection concept. An example is an inner overload situation in which traditional protection concepts will no longer trigger as the
overload currents do not pass the sensing
points of the installed protection system.
Resulting Questions
The underlying basic problem is that the limit of the proper operation of the installed
protection systems is not yet as well quantifiable as necessary. Single case investigations as done by protection divisions and
by researchers offer appropriate solutions
for specific distribution system cases. Yet,
it does not seem possible to transfer those
specific results efficiently to the broad range of diverse distribution systems today and
in the future.
The mentioned single case investigations
will not become superfluous as knowledge
of the functional limits of traditional protections system rises. Development of methods to gain this knowledge in a more general way will be a key to efficiently answer
the following questions for a huge number
of distribution systems:
• In which distribution systems exist a
need for an adaption of the protection system?
• Is it possible to develop rules, which
allow for a quick and efficient esti-
• Of what amount is the actual and foreseeable necessity of adaptions in
the distribution systems?
• Will functional limits of the protection concepts be reached without prior
violation of other restrictions (voltage maintenance, steady state current
carrying capability)?
• Which measures will be applicable
to preserve the traditional protection
system functionality?
• Which requirements apply to newly
designed protection concepts?
• Which measures are economically
and technically appropriate?
The still unreached identification of functional limits of the traditional protection systems is due to the new complexity of protection investigations.
At the moment a project to answer the above questions is actively developed by the Institute for High Voltage Technology in close cooperation with industrial partners. As a
first step a simulative analysis will be conduct therein. Secondly, the necessary modeling and the results will be validated on real
distributions systems in the test and verification center of IFHT.
mation without detailed modelling of
the single case?
Kontakt
[email protected]
+49 241 80-90015
51
52
Life Management of Power Transformers
based on Online Monitoring Data
Life management of power transformers aims to operate them close to the end of their
lifetime. This report emphasizes on the prediction of their remnant lifetime regarding aging
of solid insulation by different operation scenarios. The work covers enhancing the aging
model by considering more vital aging causes, investigating the correlation of operation to
aging, and developing the remnant lifetime forecasting approaches. Time-series data from
an online monitoring system are employed.
Introduction
The condition of the solid insulation is irreversible. Thus, the transformer’s lifetime
is generally constrained by its solid insulation lifetime. A well-known end-point
criterion is the degree of polymerization
(DP) of 200. However, the transformer has
to be out of service in order to cut some
parts of the paper for this test and therefore
the condition cannot be assessed continuously. Hence, an approach to derive aging
according to its causes which are related to
the operation is the means to acquire aging
characteristics and is the main goal of this
work. This information can assist decision
making in order to choose the optimal action on the transformers, e.g. limiting the
overloading, controlling the cooling units,
doing the drying process or planning for the
relocation or replacement of the aged units.
The research overview is shown in Fig.1.
Fig. 1: Overview of this research
Aging model by fuzzy logic approach
The solid insulation is made mainly of cellulose and therefore deteriorates over time
due to three main causes; heat, water and
oxygen. In order to ease and enhance the
verification of the aging model with actual data from a large population of transformers, the model is firstly developed by
a fuzzy logic approach (FL) based on experiment results from [1]. Hotspot temperature (HST) and water in paper (WIP)
are used as inputs. Oxygen, which is another main cause for aging, is not taken
into account in these models because it is
mostly kept in low level by the oil preservation system [2]. The rate of aging is
the outcome of the fuzzy model. The age
can be finally derived by the summation
of all results from the multiplication of
rate of aging and time interval. The developed procedures can be seen in Fig.2.
Fig. 2: Age derivation by FL
The zero-order Sugeno model, a precise
fuzzy logic model, is employed here due to
its computational efficiency.
Influence of operation on aging
The top oil temperature (TOT) is for calculating the HST. The neural network (NN)
may become a useful tool for determining the TOT. Time-series data from historical databases belonging to a monitoring system of a 5-years-in-service transformer for about 2 years are used to train
the network. This sample transformer is
Fig. 3: Layouts of developed neural networks
Here, the measured TOT is employed as
test input for the case RNN1, and the TOT
resulting from the previous time of the
same model, is used for the case RNN2.
The mean absolute error (MAE) between
measured and computed TOT defines the
breaking condition and is the main factor
to evaluate the performance of the model.
Moreover, the absolute error distribution
of all data of each method is also investigated. In some cases, the maximum absolute error (Max AE) is really high due
to abnormal operation. The performance
of all developed methods and conventional
calculation method are shown in the table below. Test data1 refers to timeseries data acquired for 150 days while
test data2 is the data measured for 3 years.
Methods
Train
data
SNN1
SNN2
TPNN
RNN1
RNN2
3.22
2.58
2.51
0.17
0.17
MAE( ◦ C)
Test
Test
data1 data2
3.80
3.14
3.24
0.22
3.20
3.47
3.12
2.94
0.34
5.87
Max AE( ◦ C)
90%
95%
of test
of test
data2
data2
7.78
10.32
5.73
7.16
5.73
7.02
0.82
1.28
16.43
25.95
The obtained results from both SNN models together with the measured TOT are illustrated in Fig.4. By taking the status of
cooling units into account as SNN2, the
computed results are closer to the measured
ones, especially during strong variation periods of current or ambient temperature.
800
TOT by measurement
TOT by SNN1
TOT by SNN2
Load current
75
700
Current (A)
Top oil temperature (°C)
85
65
600
55
500
45
400
75
76
77
78
79
80
Time (days)
81
82
83
84
Fig. 4: Measured and computed top oil temperature by SNN1 and SNN2
SNN2 and TPNN provide almost the same
performance because here the applied input
data are the measured data. The amount of
test data gives nearly no effect to their performance. Therefore, these methods can be
used for long term forecasting purposes.
characterized by 350 MVA, 400kV, and an
OFAF cooling type. The feed-forward architecture consisting of one hidden layer is
used here. The networks are trained by the
Levenberg-Marquardt algorithm. The activation function of the hidden layer is the
sigmoid and a linear function is assigned to
the output layer. Static NN (SNN), temporal processing NN (TPNN) and recurrent NN (RNN) [3], are applied in this
work and their layouts are shown in Fig.3.
Approach to forecast aging characteristics
In order to forecast aging characteristics,
extrapolation of existing data is not possible
due to its dependencies on several factors.
The profiles of aging relevant factors are
derived by a pattern learning approach and
used for forecasting purposes. Statistical
and clustering methods are used for achieving the daily and yearly patterns of ambient temperature and load current from timeseries data. Both are deployed together by
the modulation principle.
Implementation and results
The developed aging models are fed with
data from the sample transformers being in
service for 5 years. Its prognostic aging
behavior is forecasted with three operation
scenarios:
• Scenario 1: values of ambient temperature, load current and water in
oil are annually constant as from
their profiles
53
• Scenario 3: load current is limited at
only 50%.
The simulated aging characteristics are presented in Fig.5.
15
9
References
6
Age of 5−year−in−service
Prognostic age with scenario1
3
0
0
5
10
15
20
25
30
35
Time (years)
40
45
50
55
60
Fig. 5: Predicted aging characteristics
Based on the nominal lifetime of 15 years
and the prediction with scenario 1, the remnant lifetime of this transformer is around
16 years. By considering load growth, the
remnant lifetime is reduced, while it is increased by limiting load.
54
acteristics of power transformers including aging from the commissioning until the
present and also the prognostic one can be
derived by the developed approaches. The
remnant lifetimes can be achieved by different operation scenarios. This information is
helpful to support decision making for network operators, maintenance personal and
network planners.
12
Age (years)
• Scenario 2: load growth is assumed
as 3% per year and
Conclusion
The aging models based on the experiment
results from [1] are developed. The rate of
aging for each period of time can be derived
according to HST and WIP. The fuzzy logic
approach is applied in order to make the
models suitable for verification and adjustment by a numerical method with the actual
data. The neural network approach is applied for computing TOT. The aging char-
[1] A. M. Emsley and G. C. Stevens,
Review of chemical indicators of
degradation of cellulosic electrical
paper insulation in oil-filled transformers, IEEE Proceedings Science,
Measurement and Technology, 1994.
[2] IEEE guide for loading mineral-oilimmersed transformers. IEEE Std.
C57-91-1995.
[3] Q. He, J. Si and D. J. Tylavsky,
Prediction of top-oil temperature for
transformers using neural networks,
IEEE Transactions on Power Delivery, 2000.
Contact
Tirinya Cheumchit, M.Sc.
[email protected]
+49 241 80-94937
Since January 2009, the financial resources which are available to a german network operator are reduced by the efficiency requirements of the legally valid incentive regulation.
At the same time, share of power system components with increased age - due to the electricity grid expansion in the 60s and 70s - necessitates replacement investments, whereas
the cost pressure is additionaly increased. To mitigate these constraints, short term operational costs can be saved depending on the chosen maintenance strategy. The capital costs,
however, can only be adjusted in the long term, so the cost development determined by the
chosen maintenance strategy of a system operator is of fundamental importance for the development of an optimal asset management strategy. This article discusses techniques for
optimizing maintenance and to determine the influence of these measures on the revenue
cap development.
Introduction
In order to reduce costs, maintenance offers
a considerable potential for optimizations.
Annually about 1-1.5 percent of the replacement value of the network is invested
in maintenance [1]. The saving of costs in
the field of operational asset management is
often associated with a decreased reliability of the equipment. Therefore to maintain
a high level of network performance quality, the influence of maintenance on the frequency of interruptions in the asset strategy
has to be observed. In the incentive regulation, the reliability is taken into account
by a so called „element of grid-quality“ (Qelement), so that there is an additional link
between the maintenance and the revenue
cap. For the network operator, this means
that by changing the maintenance strategy,
the limit of allowed revenues and therefore profit margins can be affected by the
costs and resulting quality. Analysis to depict and explain the relationship between altered maintenance strategy and the resulting cost savings are currently conducted at
the Institute of High Voltage Technology of
RWTH Aachen (IFHT). Inter alia variations
in the cycles of maintenance of the strategy and approaches for the textual adapta-
tion of measures are regarded. The influences of the incentive regulation, for example dividing total costs into different components and the planned Q-element (2012),
are as well considered. The relevance of
the latter one increases by the dynamically
rising, partly contradictory demands of customers and regulators for a sustainable high
supply quality at low costs. Since onlinemonitoring systems are economically not
feasible for many types of equipment, usually time-based maintenance is performed.
These recently used and applied maintenance measures with fixed time intervals
do not represent the most cost effective option because the uncertainty about the current condition of equipment associated with
those can lead to unnecessary or delayed
actions. Therefore in this article a new
method for status prognoses is presented,
which shall enable the transition towards
a condition-based maintenance. The cost
shares, the resulting revenue cap as well
as the Q-element are included as examples.
Due to the expected relevance of cost accounting it is presented by the example of a
distribution network.
Challenges in operative asset management
due to incentive regulation
55
Condition assessment and prognosis
In the following,
the Condition is the degree of ability of each
equipment to run the function or functions
for which it is created without any major
failures.
Here, the condition can by defined by the
degree of influence on the undisturbed use
of the investigated equipment, which shall
be quantified using a valuation model.
Starting point for structuring the valuation method is the idea that each equipment
operates as a multi-stage unit, defined by its
functions according to Cigré. In case of an
examplarily regarded circuit breaker in this
study, these are
• opening and closing on command
• switching of currents
• loss-free transmission
• the upholding of the insulation condition and
56
• protection functions [2]
Therefore the acquisition and assessment
(weighting) of all relevant parameters for
these functions of equipment are seen as a
measure of the condition.
This detection can be implemented by
online monitoring systems, which are often
already used in Germany for expensive assets such as power transformers. However,
to integrate equipments like circuit breakers
and disconnectors into the new conditionbased maintenance strategy, a procedure
operating on the basis of already available
data is required. Starting point for this
is in the considered case the information
from maintenance. With knowledge about
the development of detected minor failures
(frequency of occurrence) during maintenances it my be possible to predict the
function-relevant parameters. The procedure for condition prediction is shown in a
simplified way in the following figure.
fig. 1: Method for a data-based contition prognosis
Based on experience of past operations and
the minor failure behavior of known components the time of first maintenance is set.
In this first measure, all relevant parameters are checked and the condition (before the measure) is detected. Starting
from the results of the parameter verification their development is adapted and with
this knowledge, the following maintenance
time is set. This is done recursively, as long
as the equipment condition does not require
a replacement.
Using this method, for about 74 percent of
the regarded equipment a sufficiently accurate prediction can be reached. A further
analysis of this procedure is in progress at
IFHT.
Effect of maintenance on the revenue
cap
To evaluate whether a maintenance strategy
not only optimizes resources, but as well
represents a profitable procedure in terms
of the incentive regulation in Germany and
to assess the question of replacement or
re-operation, the relation between maintenance and revenue cap has been determined. In order to consider the Q-element
in terms of its influence, these studies were
fig. 3: Considered grid-components in the asset
simulation [2]
fig. 2: Typical failure rates of assets
Based on data taken from a study of the
„Forschungsgemeinschaft für elektrische
Anlagen und Stromwirtschaft (FGH e.V.)“
[3], a modeling of the failure rates using the
model functions displayed in fig.2 was done
by regression calculating. Assuming that
only the wear-related failures are influenced
by the maintenance, only for this exponential function there is a dependency of the
exponent c on the maintenance. The adaptation of this parameter to the respective
maintenance was done by examining different network operators with their equipment
failures and maintenance strategies. The
considered equipments can be found in fig.
3.
As a result of a reliability assessment, the
change of supply interruptions starting from
a base scenario and thus the Q-element in its
currently covered shape can be determined.
The basic scenario consists of a maintenance interval of 10 years and 2 years for inspections respectively together with an average replacement age of the considered
components of 40 years.
conducted using a representative mediumvoltage network. To simulate the impact
of maintenance on the failure behavior of
equipment, initially the relation outlined in
fig. 2 was assumed.
As a part of a complete asset simulation for an urban distribution network operator, then the profit as the difference between revenue cap and costs can be determined. The result for various maintenance
and investment scenarios shows fig. 4.
57
fig. 4: Result of the asset simulation for an average grid operator
There are three possible scenarios, which
have a nearly equal gain. The actual scenario, a scenario with more maintenance
and a scenario with increased age and increased replacement maintenance intervals.
However the latter one will have a negative impact on the image of the network
operator due to increased equipment failures, which has not been quantified here.
The scenario with increased replacement
age but increased maintenance has to be regarded as inefficient.
58
Summary
Network operators are currently faced with
major tasks that can be mapped in their entirety only by complex procedures. The incentive regulation has to be mentioned as
a relevant factor. Asset simplified simulations can help to develop estimations for the
development of the company profit. The
presented results of such simulations considering the Q-element show, that neither
the cost- nor the quality-optimizing strategy leads to the maximum profit. An exception does exist, if network operators would
operate their grids at a very low level of
quality. As the Q-element is probably limited the additional profits due to high cost
savings are in this case only partially compensated. However, additional reductions
in profit due to penalties and reputational
damage allow the conclusion that minimum
quality strategies are not sustainable anyway in reality. In general the conditionbased maintenance strategy is regarded as
cost-optimal and therefore in terms of the
incentive regulation as efficient. For this
purpose a new data-based method was presented that can adequately predict the condition of about 75 percent of the observed
circuit breakers over a period of 8 years under the given conditions. The asset simu-
lation as well as the condition forecast are
still under investigation at IFHT.
Sources
[1] J. Wilckens, Den Herausforderungen der Anreizregulierung mit
Lean Methoden begegnen, proLean Consulting AG, Online-artilce
for „Bundesverband Deutscher Unternehmensberater BDU e.V.“,2010.
[2] CIGRE WG C1.1, Asset management of transmission systems and associated CIGRE activities, 2006.
[3] U. Zickler, A. Schnettler, Betriebsmittelstatistiken für das AssetManagement: Möglichkeiten und
Nutzen, FGH-Conference „AssetManagement in Verteilungsnetzen;
Methoden, Daten, Praxiserfahrungen“, Heidelberg 2006.
Contact
Dipl.-Ing. Christian Hille
[email protected]
+49 241 80-94915
Field of Research: Fault Arcs
Although fault arcs occur seldomly in electrical installations, they do not only put a risk
on the operation personnel but also have a serious impact on the installations and the
switchgear building by the exhaust of hot gas and the consequent pressure rise. Hence, these
consequences have to be considered during the planning phase and the dimensioning of the
installation in order to limit the pressure rise to acceptable values, e. g. by construction
measures. For this purpose calculation methods are employed to determine the expectable
pressure rise in case of a fault. The presented ISC method (Improved Standard Calculation),
a development based on the established PRESSURE-software, allows a fast and reliable
pressure calculation considering energy absorbers, gas mixtures of air and SF6 , and any
number of rooms or volumes.
Improved Calculation Method for the Pressure Rise due to Fault Arcs
Introduction
In case of a fault arc (internal fault) in
a medium-voltage switchgear an electric
power in the order of several tens of MW
is dissipated leading to a temperature rise
in the insulation gas and a consequent
pressure rise in the arc-affected switchgear
compartment. To prevent an uncontrolled
burst of the containment, the pressure is
released through relief openings or ducts
into other volumes of the switchgear or the
building, the switchgear is installed in. The
energy transported by the gas flow subconsequently leads to a pressure rise in these
volumes. The mechanical strength of these
rooms against overpressure is limited and
only amounts up to 10 mbar for brick walls,
for example. Hence, the pressure stress especially of the switchgear building has to
be considered carefully in the pressure calculation process [1].
59
Fundamentals of Pressure Calculation
Fig. 1: Basic principle of this calculation
method PRESSURE
The software PRESSURE, which is used
for pressure calculation so far, is based
on the solution of the fluid dynamic equations and the first law of thermodynamics [2]. The basic principle of this calculation method is depicted in Fig. 1.
The pressure rise ∆p in the fault affected
compartment (arc room) VAR within a calculation time step ∆t depends on the electric power of the arc Parc , the thermal
transfer coefficient kp and especially on the
60
properties of the insulation gas expressed
by its adiabatic index κ:
∆p =
(κ − 1) · kp · Parc · ∆t
.
VAR
The mass ∆m, exhausted within a calculation time step ∆t through an opening
(area A, discharge coefficient α) is determined by the density ρ and the flow velocity v of the gas:
∆m = α · A · ρ · v · ∆t.
These equations together with the determination equation for the temperature rise
∆T form a system of differential equations,
which is solved iteratetively for all volumes
of the considered arrangement using the
Runge-Kutta method. This solution process
finally yields in a spatially averaged pressure development for the entire switchgear
and the building. The quality of the pressure calculation depends on the accuracy of
the input data. Especially, the arc voltage
Uarc , determining the dissipated arc power
Parc , and the temporal variation of the energy transfer coefficient kp as a function of
the gas density have to be taken under consideration. Furthermore, a reliable pressure
calculation requires accurate gas data [3].
For instance, small deviations of the adibatic index of SF6, which is only marginally
greater than one, can already lead to significant errors in the calculated pressure rise.
Functionality of the ISC Method
The established PRESSURE-software,
which is based on the so-called standard
calculation method [2], has been extended
and developed at IFHT in the scope of the
publicly funded research project Reduction
of Pressure Stress in Electrical Installations due to Internal Arcing supported by
the German Federation of Industrial Research Associations (AiF). This development mainly includes the integration of ad-
ditional functionalities and leads to the Improved Standard Calculation (ISC) method,
which constitutes a considerable progress
in comparison with previous calculation
methods.
Whereas the PRESSURE-software only allows the pressure calculation for standard
applications with three compartments and
one opening each, neither the number of
volumes and openings nor their arrangement is now limited in the ISC method.
This allows the calculation even for complex installation layouts, in which several
relief openings into different relief rooms
are used simultaneously, for example. The
integration of arc energy absorbers, used
in relief openings and ducts to reduce the
energy content of the exhaust gas, is an important issue of the ISC method. Employing a physical model, both the absorption
of energy and the flow resistance are implemented [4].
Another feature of the ISC method is the
possibility to calculate the pressure rise
not only for air-insulated, but also for
SF6-insulated switchgear. The calculation
method considers the mixing of the insulation gas exhausted from the arc-effected
compartment with the ambient air in the
other volumes of the switchgear and the
building, respectively. Hence, the variation
of the gas properties is taken into account.
The input data is based on real gas data and
the physical gas properties are determined
by spline-interpolation from pre-calculated
tables. Thus, a high accuracy in the determination of the gas data is achieved, leading
to a significant increase of the reliability of
the entire pressure calculation process [4].
The ISC-software provides a graphical user
interface, which allows a fast and efficient
operation of the calculation tool. Due to
the realization in the JAVA®-environment,
the implementation is independent from the
operating system.
The input values for the arc voltage and
the kp -factor are derived from a broad data
Field of Research: Fault Arcs
Conclusion
Having developed the Improved Standard
Calculation method , a pressure calculation
tool is available, which features by a minimum of restrictive pre-conditions, a high
degree of variability, and the use of real gas
data. This allows a reliable pressure calculation in a wide range of medium-voltage
applications for both air and SF6-insulated
switchgear.
The ISC-software is ideally suited to eval-
uate other spatially-averaging pressure calculation methods.
References
[1] Schumacher M.: Untersuchungen
zur Modellierung der Druckbelastung von Schaltanlagengebäuden
durch Störlichtbögen, Ph.D.Thesis,
RWTH Aachen, 1994
[2] Friberg, G.: Berechnungsverfahren
zur Bestimmung der Druckbelastung
in elektrischen Anlagen im Störlichtbogenfall, Ph.D.Thesis,
RWTH Aachen, 1998
[3] Anantavanich, K., Pietsch G., Eichhoff, D.: Importance of SF6-air gas
data for pressure calculation due to
fault arcs in electrical installations,
XVIII International Conference on
Gas Discharges and their Applications, Greifswald, 2010
[4] Anantavanich, K.: Calculation of
Pressure Rise in Electrical Installations due to Internal Arcs Considering SF6-Air Mixtures and Arc Energie Absorbers, Ph.D.Thesis,
RWTH Aachen, 2010
Contact
[email protected]
+49 241 80-97348
base, containing reliable values for these
figures. By means of a integrated module
for the calculation of the electric arc power
Parc the required input values are immediately available for the pressure calculation.
The possibility to consider the response
pressure of relief openings and rupture
disks further increases the degree of variability in switchgear layouts. Hence, the
ISC method covers a wide range of application and is able to calculate the pressure
rise for nearly all commonly installed configurations of medium-voltage switchgear
without any restrictions concering special
types of switchgear, single manufacturers,
or building layouts.
As the ISC-software outputs not only the
calculated pressure but also further physical
values like the gas density or the temperature, the user is able to check the plausibility of the results immediately. In contrast
to spatially-resolved calculation methods,
which usually require a simulation time
of several hours, the pressure calculation
of the ISC-software is completed within a
short period of time.
61
Calculation of Pressure Rise in Electrical Installations due to Internal Arcs Considering
SF6-Air Mixtures and Arc Energy Absorbers
PhD Thesis: M.Sc. Kittipong Anantavanich
Date of the oral examination: March 5th, 2010
Reporter:
Univ.-Prof. Dr.rer.nat. Gerhard Pietsch
Univ.-Prof. Dr.-Ing. Hans-Jürgen Haubrich
Nowadays, there exist already reliable pressure calculation methods, which are able to determine pressure rise in electrical installations and corresponding buildings due to internal
arcs. However, up to now none of them is able to consider SF6 -air mixtures, which are
of importance particularly in SF6 -insulated medium voltage switchgear installations. The
same is true for arc energy absorbers, which are recently installed with an increasing number. However, their current modelling must be improved and the implementation in pressure
calculation methods validated. In this thesis, the aforementioned drawbacks of existent
calculation methods are overcome in implementing SF6 -air mixtures and the effects of arc
energy absorbers in pressure calculation methods.
Introduction
62
Internal arcs cause sudden temperature and
thus pressure increase in electrical installations, which may endanger personnel,
electrical equipment, installation rooms or
buildings as well as the security of power
supply.
The proof of internal arc withstand is usually performed by tests in high power laboratories or by pressure calculation especially in cases, where tests are not possible
or impractical.
Nowadays, there exist reliable pressure calculation methods, which can determine the
pressure development during internal arcing. Two kinds of calculation methods have
been proved to be necessary for practical
applications. The first one is the so-called
“CFD calculation method”, which delivers
spatially resolved results including all relevant physical effects e.g. pressure waves
by solving the fundamental hydrodynamic
equations with a Computational Fluid Dynamics (CFD) solver. The second one is the
“standard calculation method”, which provides spatially averaged results rather fast
by solving a simplified equation system.
The application area of these calculation
methods is so far limited. This is especially true for SF6 -insulated switchgear installations with (air-insulated) pressure relief rooms, in which SF6 -air-flows with
varying SF6 concentration occur, and for
switchgear installations with arc energy absorbers. The objective of this thesis is to
include SF6 -air mixtures and arc energy absorbers into both pressure calculation methods for general applications and to further
develop the computer program based on the
standard calculation method.
Modelling of SF6 -Air Mixtures and
Arc Energy Absorbers
The focal point of the description of SF6 air mixtures is the generation and treatment
of gas data with changing gas composition.
For the generation of these gas data, there
exist two possibilities, which are on the one
Dissertations
Fig. 1: Effect of absorbers
Arc energy absorbers have influence on the
pressure development by two ways, through
heat absorption and flow resistance (Fig. 1).
In order to desribe these effects, different
existing as well as newly introduced model
approaches are analysed.
determined by interpolation. For this purpose an optimisation of the interpolation
process is carried out to achieve fast convergence with numerous iterations with the
CFD calculation method (in short “CFD
method”) resulting in reasonable computing times. In order to determine the changing gas compositions in the flow domain,
an additional conservation equation for SF6
mass fraction is introduced.
For the implementation of absorbers the
absorbed heat energy and the pressure loss
have to be included into the fundamental
hydrodynamic equations. This is done by
introducing heat sinks into the conservation
equation of energy and friction forces into
the conservation equation of momentum.
Standard calculation method
With the standard calculation method the
SF6 mass fraction is directly included into
the equation system. Real gas data depending on pressure, temperature and gas composition are also used here.
In order to include the effects of absorbers,
the grid efficiency is chosen to describe
the heat absorption and the flow resistance
is considered by a concentrated effective
opening. The absorbed heat energy is included into the equation system through
heat sink and the flow resistance through
the discharge coefficient.
Based on the standard calculation method
with the newly introduced extensions, a
new software package for the calculation
of pressure rise due to internal arcs is developed (Improved Standard Calculation
(ISC) Method). The program is written in
Java and thus platform independent.
Implementation of Gas Mixtures and
Arc Energy Absorbers in the CFD
and Standard Calculation Method
Validation
CFD calculation method
During pressure calculation, gas data of SF6
air mixtures are obtained from the threedimensional table. Intermediate values are
The CFD and ISC methods are validated
with the inclusion of SF6 -air mixtures and
arc energy absorbers. This is achieved
by comparing experimental with calculated pressure and temperature develop-
hand the application of ideal gas mixing
laws with temperature and pressure dependent gas data of the components and on the
other hand the minimisation of Gibbs free
energy of all components together with the
solution of the Boltzmann equation. With
the first possibility, interactions including
chemical reactions between the gas components are not taken into account. With the
help of two examples, it is demonstrated
that the consideration of interactions and
chemical reactions is necessary.
In order to obtain reasonable computing
times, the gas data cannot be generated in
every iteration step during the solution of
the differential equation system. Therefore,
they are provided in a three-dimensional
table with reference values depending on
pressure, temperature and gas composition
(SF6 mass fraction).
63
room are depicted.
3.5
switch compartment (ISC method)
relief room (ISC method)
switch compartment (CFD method)
Pressure (bar)
3.0
relief room (CFD method)
switch compartment (measurement)
relief room (measurement)
2.5
2.0
1.5
1.0
0
100
200
300
400
Time (ms)
Fig. 3: Measured and calculated pressure developments in the switch compartment and
the relief room (air test)
1.04
ISC method
CFD method
measurement
1.03
Pressure (bar)
ments, respectively. In total six arrangements are investigated. The dimensions of
the six arrangements under investigation
cover a wide range of application, which
is typically found in medium voltage (MV)
switchgear with SF6 -insulated faulty compartments.
In the following, a comparison with one of
the investigated arrangements is shown as
an example. It consists of a compact MV
switchgear installation (Fig. 2). A five-layer
arc energy absorber is installed between the
relief and the transformer room. The switch
compartment is filled with air and SF6 , respectively (air test: 12.7 kA, 0.76 s; SF6
test: 16 kA, 1s).
The results from the ISC and CFD method
are compared with those from measurements. With the CFD method the model
approach “in-line tube bundles” is applied
for the heat transfer and that of “crossed
in-line tube bundles” for the pressure loss.
1.02
1.01
1.00
0
100
200
300
400
Time (ms)
64
Fig. 4: Measured and calculated pressure developments in the transformer room (air
test)
1.25
1.20
ISC method
CFD method
Pressure (bar)
measurement
1.15
1.10
1.05
Fig. 2: Schematic arrangement of the MV
switchgear installation with effective
volumes (SC: switch compartment, RR:
relief room, TR: transformer room)
In Fig. 3 and 4 the pressure developments
in the switch compartment, the relief room,
and the transformer room in case of the air
test are shown.
In Fig. 5 the measured and calculated pressure developments in the relief room in
case of the SF6 test without the transformer
1.00
0
200
400
600
800
1000
Time (ms)
Fig. 5: Measured and calculated pressure developments in the relief room without the
transformer room (SF6 test)
The results of the validation for the CFD
and ISC method can be summarized as follows:
CFD method
Dissertations
ISC method
In general the ISC method yields reliable
results as long as pressure waves and gas
flows do not dominate the pressure development.
Conclusion
The significant results of this thesis are related to the modelling and inclusion of SF6 air mixtures as well as the inclusion of the
effect of arc energy absorbers into the pressure calculation methods (CFD and standard calculation method) for general applications.
The main concept of the modelling of SF6 -
air mixtures is the consideration of gas mixture properties with varying mixing ratio
during the gas flow of SF6 into surrounding air. For this purpose the gas composition must be determined during the calculation. In order to take into account all
important effects, which have influence on
the pressure development, real gas data are
applied. The inclusion of SF6 -air mixtures into both considered pressure calculation methods leads to reliable calculation
results.
Arc energy absorbers influence the pressure development through heat absorption
and flow resistance. In order to describe
both effects, existing approaches are analysed and improved. The inclusion of both
effects into the pressure calculation methods is achieved by introducing heat sinks
and friction forces into the corresponding
conservation equations. Accordingly, reliable results are obtained.
Based on the standard calculation method
together with the inclusion of mixtures and
absorbers, a platform independent computer program is developed, which gives
fast results, is simple to handle, and is suitable for a wide range of application.
Contact
Dr.-Ing. Kittipong Anantavanich
[email protected]
+66 2 436 1312
Regarding SF6 -insulated switchgear, the
CFD method delivers reliable results. For a
wide range of application, real gas data of
mixtures must be applied, which consider
interactions between the components of the
insulating gas including chemical reactions.
In order to describe the heat absorption and
the flow resistance of absorbers simultaneously, two model combinations are proposed concerning the applicability. The first
combination (grid efficiency approach for
the heat absorption and an effective opening for the flow resistance) is suitable, if
measuring data are available. If not, a second combination (in-line tube bundles for
the heat absorption and crossed in-line tube
bundles for the flow resistance) is recommended.
65
Modeling the type specific failure occurrences of high voltage switching equipment
PhD Thesis: Dipl.-Ing. Stefan Federlein
Date of oral examination: April, 29th, 2010
Reporter:
Univ.-Prof. Dr.-Ing. Gerd Balzer
On the basis of an efficient asset management network operators will be able to optimize
their future operation. Therefore, knowledge about age dependant failure occurrences of
equipment has to be integrated into the asset management software tools of network operators. Precise predictions for future equipment behavior will help network operators in the
decision making process. This thesis deals with models describing the type specific and age
dependant failure occurrences in consideration of applied maintenance actions. Using the
example of different types of circuit breakers, first the ageing behavior in case of the current
maintenance and following in case of modified maintenance scenarios will be modeled and
investigated.
Introduction and motivation
66
Increasing cost pressure due to regulatory
guidelines, changing topology of electrical power generation as well as ageing of
equipment and very volatile load flows are
the main challenges for transmission and
distribution system operators.
Minimizing the total cost and providing a high security of supply at the same
time are the major aims of system operators. An efficient asset management will
help to achieve these aims. The optimal
usage of equipment as well as determining their maximal lifetime are the essential
aspects in this optimisation process. One
of the basic requirements is a comprehensive knowledge about equipment, their type
specific behaviour as well as the impact of
maintenance strategies on minor and major
failure occurrences.
Modeling the type specific failure occurrences of high voltage circuit breakers
in consideration of applied maintenance actions is the main objective of this thesis.
Especially, it is focused on the correlation
between failures and the specification of
maintenance actions. Following the point
of view is not a comprehensive network
system but rather on an certain high voltage
equipment (123 kV and 245 kV outdoor circuit breakers).
Database
In cooperation with German network operators a database is established. It includes essential information of outdoor substations e.g. technical data, failures, operating times, maintenance data. Afterwards five circuit breaker types were identified whose available data is adequate to the
modeling and the application.
In addition numerous maintenance protocols will be captured and evaluated which
was not done before. The findings during
maintenance actions are now available as a
so called bit mask that presents the condition at maintenance time. Following all minor failures are collected in that way.
Dissertations
The basic for the following model is the
evaluation of the ageing behavior considering the current applied maintenance actions. Built on empiric knowledge the
failure model in case of current maintenance actions will be developed and applied
on five representative circuit breaker types.
The resultant ageing models show a bath
tub curve approach (see figure 3); thereby
the specific differences in the behavior of
the considered equipment could be pointed
out clearly.
ing truncated Weibull distributions the expert knowledge is formulated mathematically. Theses functions are integrated in the
model as a time dependant failure probability. The probabilistic progression from
a minor to a major failure is attended by
a time dependant and not regenerative random process.
Hence, the model estimates the failure
occurrence after the normal service interval
is exceeded is thus apparent as a superposition of the current failure occurrence λ(t)
with the additional failures which occur as
a result of a damage ∆λ(t). Therefore, for
the changed behaviour, the following resultant failure occurrence λ′ (t) is produced by
′
λ (t) = λ(t) + ∆λ(t) = λ(t) +
n
X
Failure occurrences by current maintenance
∆λi (t)
i=1
Fig. 1: Failure occurrences of different circuit
breakers by current maintenance
The teething items of the circuit breakers
cover the first years up to two till eight
years. With the exception of one breaker,
all ageing and burn-out phenomena start
in average between 10 and 15 operating
years. Afterwards failures could increase
extremely. The average failure rate is in a
range of two to eight failures per 100 circuit breaker years.
Progression of a minor to a major
failure occurrence - m2M-Model
Based on heuristic knowledge, inspected
damages (minor failures) during maintenance actions and current failure occurrences a new model called m2M1 is developed. This m2M model evaluates the
impact of deferred maintenance actions on
the failure occurrences. In this process, us1
n describes the maximum of different damage types i which can be inspected during
maintenance actions. By means of the truncated Weibull distributions deduced from
expert knowledge, the probability pi (t) for
a failure occurrence at time t can be delivered. In consequence ∆λi (t) is calculated
by
∆λi (t) = pi (t) ·
t−1
Y
( 1 − pi (j) ) · hi, IHM
j=1
In this case, the second factor illustrates the
probability, that the minor failure has not
entailed a major failure in the time period
before time t (not regenerative process).
The relative minor failure frequency is represented by hi, IHM and weights the failure
occurrence accordingly.
Failure occurrences by modified
maintenance
In this thesis 14 scenarios are considered. The deferred maintenance intervals
(in years) always refer to the basic scenario
m2M: minor to Major failure
67
0/0 with an inspection interval of two years
and a service interval of eight years. Consequently, scenario 1/2 illustrates inspection
intervals of three years and service intervals
of ten years.
Figure 2 shows the ageing behavior for
three different scenarios. It is obvious,
that already a slight extension of maintenance intervals induce a significant increase
of failure occurrences (scenario 1/2). Furthermore, a scenario with very long maintenance intervals (e.g. scenario 4/8) procures increasing failure occurrences that are
disproportionate higher than the extension
of the maintenance intervals. This effect
belongs to minor failures with long progression times for m2M, because these minor failures will develop to major failures
only in combination with long time intervals. Considering short intervals, these
minor failures will not induce major failures and consequently they have no negative effect on the failure occurrences.
tenance effort is reduced by 45 percent.
Fig. 3: Failure occurrences in different maintenance scenarios
68
Fig. 4: Maintenance effort in different scenarios
Fig. 2: Maintenance scenarios for a 123 kV circuit breaker
Figure 3 and figure 4 compare all considered scenarios. The expected changes
in failure occurrences as well as in maintenance efforts (= fix costs) are compared to the basic scenario 0/0. Considering the very low failure rates of circuit breakers in any case, the scenario 2/4
seems to be very efficient. On the one
hand the failure occurrence increases three
times, but on the other hand the main-
The application of the m2M model on three
types of circuit breakers presents plausible
results and the following consequences can
be drawn out.
According to the resultant failure rates
the extension of maintenance intervals is
tend to be defensible. Tough the type specific differences of the circuit breakers have
to be considered. In dependence on the
technical characteristics already slight extensions of the intervals will induce a very
high failure potential.
Independent on the circuit breaker
types, the efficiency according to deferred
maintenance intervals increases easily. An
Dissertations
Furthermore, the analysis of damages
shows, that especially the first service action is able to detect many damages, which
often refers to teething items. In that case,
it is recommended to hold the first service
action at the current time (eighth operating
year) and to defer the following service cycles only. Hence, the potential of failure occurrences will not exhaust in the first operating years.
Conclusion
In this thesis a new model is developed,
which describes the progression from a minor to a major failure (m2M). This model
predicts the resultant failure occurrences in
case of change maintenance actions. The
application of the m2M model is reviewed
using the example of circuit breakers. Now,
the model is available for network operators
to assess other equipment in dependence on
the available data.
References
[1] S. Federlein, C. Hille; C. Neumann,
B. Rusek, A. Schnettler: Nutzung
historischer Instandhaltungsinformationen zur Modellierung des Betriebsmittelverhaltens. International
ETG Congress, FT4 - 5.1, Duesseldorf 2009
[2] S. Federlein, C. Hille, A. Gaul, A.
Schnettler: New methods to assess
the impact of maintenance and the
condition of network. CIRED 2009,
Session 1, No. 0870, Prague (Czech
Republic) 2009
inspection can detect only less critical damages and is in consequence less effective.
Contact
Dr.-Ing. Stefan Federlein
[email protected]
+49 (241) 80-94959
69
70
Elastic Syntactic Foam in High Voltage Applications
PhD Thesis: Dr.-Ing. Michael Kessler
Date of oral examination: July, 2nd, 2010
Reporter:
Univ.-Prof. Dr.-Ing. Volker Hinrichsen
Future insulation systems have to be lighter and more compact than those used today. Nevertheless they must be reliable and feature a long lifetime. Additionally, due to a general
increased environmental awareness of the customers, environment-friendly materials are
demanded. A non-combustible, solid material is insensitive to leakages in housings, which
may occur when gaseous or liquid insulation materials are used and may lead to faults
and environmental hazards. Using an elastic and compressible solid material also avoids
crack formation, which may occur in conventional solids under thermal load cycles. Elastic
syntactic foam is a promising material for this task. This kind of composite material consists of a silicone matrix and gas-filled polymeric microspheres in a range of several 10 µm
used as filler. In this work, mechanical and physical properties of elastic syntactic foams
depending on their constellation are investigated. The focus is on the electrical properties
in the short term range. Moreover, the behavior of this material under electrical field stress
is investigated with the aim to develop a model describing the processes during an electrical breakdown for AC and DC voltages. The investigations show that discharge structures
generally are located in the silicone elastomer. Hence the breakdown process for AC and
DC voltage in elastic syntactic foam is an electrical breakdown inside the silicone matrix.
Introduction and motivation
There is a variety of demands on modern
insulation systems for high voltage applications. Not only electrical ageing but also
thermal stress is a challenge for materials.
As a result of changing weather conditions
or fluctuating load, thermal load cycles lead
to mechanical stress inside the insulation
system. Crack building inside the housing
or ablation of the insulating material leading to a breakdow and outage may occur.
Gaseous insulation materials like Sulfurhexafluorite (SF6) or liquid materials
(e.g. transformer oil) are commonly used
in high or extra high voltage applications.
The requirement to avoid leakages is a serious disadvantage, since leaking of the in-
sulation material is harmful to the environment and leads to a reduction of the dielectric strength with a breakdown as last consequence. A solid material avoids the disadvantages mentioned above (a so called
“dry” Insulation material [1]). However,
high temperature gradients are a danger to
solid materials. A possible solution for this
task is an insulation material filled into the
component in the liquid state curing there
to solid material. A high elasticity, compressibility and a strong adhesivity to other
solids make a material able to withstand
thermal load cycles. Such a solid material is called elastic syntactic foam. This
material consists of a silicone gel matrix
with a low viscosity and polymeric microspheres in a dimension of some 10 µm used
Dissertations
Fig. 2: Dielectric strength of different elastic
syntactic foams depending on the filling
degree
Fig. 1: ESEM picture of an elastic syntactic
foam [2]
New application fields for elastic syntactic foams are ignition systems. Due to the
strong temperature gradients in the engine
compartment during motor start or as a result of splash water contact during drive in
winter times, there is a serious temperature
stress for components. As a consequence of
the thermal stress crack building may occur
in traditional epoxy-based insualtion systems.
Since the intervals are overlapping, no binding statement can be made. There is also
broad scattering for 20 Vol.-% filling degree under AC stress. The results for all
elastic syntactic foams are around 25 %
lower in comparison with pure silicone gel
(0 Vol.-% in Fig. 2). The average dielectric
strength of pure silicone gel under AC stress
is 71.4 kV/mm (peak value). A similar
trend is found for DC investigation. There
is a slight increase of the average dielectric
strength with increasing filling degree. The
influence of the inorganic coating on the dielectric strength is shown in Fig. 3.
Short time dielectric strength
One focus of this work is on the investigation of the dielectric strength of elastic
syntactic foam under AC and DC stress depending on several parameters. A sphere
to sphere arrangement of electrodes is used
for the investigations (diameter of spheres
12 mm, sparking distance 3 mm). The evaluation is done using the 95 % confidence
interval. Peak values are given for AC results. If calcium carbonate coated microspheres are used as filler, a slight increase of
the dielectric strength with increasing filling degree can be found for AC (Fig. 2).
Fig. 3: Dielectric strength of elastic syntactic
foams depending on coating
With calcium carbonate coated microspheres (average diameter 90 µm) and uncoated microspheres (ca. 80 µm) are considered with 40 Vol.% filling degree respectively. The average dielectric strength of
syntactic foams filled with coated spheres
as filler. Fig. 1 shows an ESEM (Environmental Scanning Electron Microscopy) picture of elastic syntactic foam. This material combines the excellent adhesion of the
silicone gel to other polymeric and metallic
surfaces with the compressibility of the gas
filled microspheres.
71
72
is 54.3 kV/mm for AC. Hence, it is 76 %
higher than the dielectric strength for syntactic foams filled with uncoated microspheres. For DC applications, the usage of
coated microspheres leads to 93 % higher
average dielectric strength in comparison to
uncoated microspheres.
Investigations on well defined microsphere arrangements
Optical investigations form another important backing for the development of a breakdown model for DC and AC voltage. These
investigations make the detection of origin
and development of discharge channel possible. Samples of coated microspheres in
pure transparent silicone gel are considered.
To make the production process easier big
microspheres with an average diameter of
200 µm are used to build up the structures.
Fig. 4 illustrates an example of a microsphere row inside a tip to tip electrode arrangement. Fig. 5 shows the breakdown
channel. To create the channel a step test is
used (start voltage 15 kV, step 2 kV/min).
The results show that all breakdown channels proceed around the microspheres. Although the microspheres are centered between the tip electrodes and hence on the
axis of highest field strength, the discharge
channel does not proceed through the microspheres but moves them aside. Further
optical investigation in the short term range
show that the breakdown channel develops
in the silicone gel matrix independent from
the degree of homogeneity of the electrode
arrangement.
Fig. 4: Microcsphere arrangement in silicone
gel
Fig. 5: Microsphere arrangement after breakdown
For the determination of the field distribution inside well defined microsphere
arrangements, simulations are performed.
A three-dimensional FEM (finite elements
method) tool is applied. This tool works
with an automatic, adaptive mesh method
using tetrahedral elements. The simulations
are done with background field strength
of 20 kV/mm, since this value is lower
than the dielectric strength of pure silicone gel according the data specification.
The field distribution in the plain of central
points of an microsphere matrix is shown
as cut view in Fig. 6. The background
~ a, ∞ is vectored from left to right.
field E
Fig. 6: Simulation of the field distribution in a
microsphere matrix
The highest field strength occurs at the outermost microspheres of a row (25 kV/mm).
However, the field strength decreases locally to 15 kV/mm between two microspheres. Looking at a microsphere row
vertically to background field shows that
there is a zone of reduced field strength
(10 kV/mm) left and right of the microsphere row. But the field strength
is strongly enhanced between the micro-
Dissertations
Breakdown model
Due to the presence of microspheres field
displacements occurs inside the silicone
gel matrix leading to local field enhancements. These enhancements can activate
local discharges in the silicone gel. The
discharge process itself is known from literature: Electrons accelerated in the gas
channel cause chain scission of the silicone
[3]. If the discharge impacts on a mineral
coated microsphere, the discharge can be
hampered. Using a high filling degree of
microspheres helps to avoid the expansion
of the discharge channel as a result of the
pressure rise inside the gas channel and the
elasticity of the silicone gel matrix. Is the
discharge process able to continue around
the microsphere and bridge the complete
insulation distance, the high short circuit
current destroys the thermoplastic sphere
shells thermally. Since the investigation
deliver comparable results, the breakdown
model is valuable for DC and AC voltage.
References
[1] Eitle, R.; Kaumanns, J.: Trockene
Freiluftendverschlüsse
mit
Stützeigenschaft, Fachbeitrag aus
Elektrizitätswirtschaft; Heft 11.2000
[2] Keßler, M.: Einsatz elastischer
syntaktischer Schäume in der
Hochspannungstechnik, Aachener
Beiträge zur HOCHSPANNUNGSTECHNIK Band 16, Verlagshaus
Mainz GmbH, 2010
[3] Oesterheld, J.:
Dielektrisches
Verhalten von SilikonelastomerIsolierungen bei hohen elektrischen
Feldstärken,Fortschr.Ber.VDI Reihe 21 Nr.196, Düsseldorf VDI Verlag, 1996
spheres. Thus the dielectric strength of the
silicone gel can be exceeded.
Contact
Dr.-Ing. Michael Kessler
[email protected]
+49 241 80-94936
73
74
Resistance Distribution in Switching Arcs of
Self-Blast Circuit Breakers at the Current
Zero Phase
Dissertation: Dr.-Ing. Ming Chark Tang, MBA
Date of oral examination: 5th March, 2010
Advisor:
Univ.-Prof. Dr.-Ing. Michael Kurrat
Self-blast circuit breakers are widely used as switching elements in electrical power systems. In case of a short-circuit fault the breaker contacts are separated leading to an ignition of an electric arc. Hence, the current flow is carried by the electric arc itself. Due
to a cooling of the arc at the current zero phase, the arc can be successfully extinguished.
The switching gap is converted from a conductive state to an insulating one. In this thesis
a measuring arrangement is developed to determine the partial resistance distribution of
the switching arc during the current zero phase. This arrangement is adapted to a selfblast circuit breaker model. The physical cooling mechanisms can be evaluated by using
an Computational Fluid Dynamics simulation of this process. Detailed knowledge of the
resistance distribution leads to a better understanding of the processes during the current
zero phase with filling gases such as SF6 and CO2. This enables further optimisation of gas
circuit breakers.
Resistance Development in Circuit
Breakers
At the current zero phase the current is decreasing towards the current zero crossing.
Thus, the ohmic heating power is decreasing at this phase. In order to achieve a successful interruption the electric arc inside a
circuit breaker has to be quenched, which
starts some microseconds before the actual
current zero crossing (see Figure 1). During
this time period the cooling power of the arc
inside a circuit breaker exceeds the ohmic
input power by the current flow. The energy
of the electric arc is decreased and the resistance of the arc is increasing. At the postarc current phase (t > 0) the transient recovery voltage is generating a current flow inside the switching arc. Due to the net loss
of energy the resistance of the electric arc is
still increasing shortly after the current zero
crossing. If the ohmic heating power of the
electric arc exceeds the cooling power the
resistance of the switching arc will reach a
maximum. Due to further re-heating of the
electric arc the resistance is decreasing to a
conductive state. Hence, the arc quenching
process is not successful. In the opposite
case the cooling power remain higher than
the ohmic heating power during all the time
after the current zero crossing. The resistance of the switching arc will increase to
a non-conductive state. Hence, the switching arc is quenched and the switching process of the circuit breaker is successful.
Dissertations
Fig. 1: Development of the current, the voltage and the resistance at the current zero
phase and at the post-arc current phase
[1]
The resistance development during the current zero phase is understood as a spatial
integrated value, which is further used as
an evaluation criteria for circuit breakers.
But no information is known about the spatial distribution of the resistance within the
switching arc. Further, the relevant physical phenomena of this process are not quite
clear. A detailed knowledge of the resistance distribution and the cooling mechanisms lead to a better physical understanding of the switching process. Hence, a more
goal-orientated analysis of gas-blast circuit
breakers with various filling gases can be
performed and further design and performance optimizations can be carried out.
Concept of Investigation
The concept of investigation is illustrated
in Figure 2. The analysis of the resistance
development and distribution and the correlating cooling mechanisms are the main
goal of this investigation. Therefore, an appropriate test arrangement is developed to
evaluate the main effects. Influences by
other parameters are minimized by the design. The test arrangement is implemented
in an experimental circuit breaker model
and a simulation model. The experimental results are used to verify the simulation
Fig. 2: Schematic Diagram of the investigation
concept
For the experiments a self-blast circuit
breaker model is used with common cylindrical nozzle shapes. Within these nozzles a measuring arrangement is integrated
to measure the partial resistances at discrete areas of the switching arc. The specific areas represent relevant areas of specific physical processes. The measuring arrangement is investigated to have a negligible influence on the basic processes at the
current zero phase of a switching operation.
A special measuring equipment is utilized
to have a high time resolution of the measuring signals during the current zero phase.
The simulations are performed with a CFD
(Computational Fluid Dynamics) software.
The main equations of a CFD solver are
based on the laws of mass conservation (Eq.
(1)), of momentum conservation (Eq. (2) (4)) and of energy conservation (Eq. (5)):
model. The simulated results are used to determine physical parameters and processes
which are not accessible to measurements.
The combined results of both approaches
are evaluated to one consistent understanding. The investigations are performed with
the filling gas SF6 on the one hand and CO2
on the other hand. The differences of the
switching behaviour of these two gases are
evaluated as well.
75
Results of the Investigations and
Analysis of the Switching Behaviour
Additionally, calculation models for turbulent effects and for radiation phenomena are
taken into account as well as the equation
for the electrical field. The test arrangement is implemented into the simulation
software. The simulation model proves to
be able to simulate the physical effects occurring during a current zero phase.
The simulated results of the SF6 circuit
breaker model and the CO2 one are presented in Figure 4 for the time 200 ns before the current zero crossing for the same
simulation conditions. On the left side of
the dashed line the results refer to the SF6
circuit breaker model whereas on the right
hand side the results refer to the CO2 circuit
breaker model. Around the stagnation area
the temperature distribution of both simulations are very similar. Especially for the
CO2 circuit breaker model a radial widening of the temperature distribution can be
observed within the nozzle. Thus, the resistance in the nozzle is smaller than that at
the area around the stagnation point. Contrary, a higher resistance distribution can be
determined in the nozzle of the SF6 circuit
breaker model.
76
Fig. 3: Illustration of the arcing area and sectionalizing into discrete resistance areas
The switching area of the self-blast circuit
breaker model is illustrated in Figure 3. It
is a static and rotational symmetric arrangement. On the left and on the right hand side
the electrodes are placed. Between these
electrodes is the arcing area. In the middle of the arrangement the flow channel of
the quenching gas is indicated. The quenching gas consists mainly of the filling gas of
the circuit breaker. The total resistance of
the switching arc is given by Rges. The total
resistance consists of the partial resistances
RDiff (resistance of the diffuser area), Ra and
Rb (resistance of two separate parts of the
nozzles) and RSP (resistance at the stagnation point area).
Fig. 4: Comparison of the temperature distribution and the resistance per length of a
SF6 circuit breaker and of a CO2 one
The experimental results are interpreted in
conjunction with the physical analysis of
the simulations. For the partial resistances
and the main cooling mechanisms (by convective cooling Pconv on the one hand and
by turbulent cooling Pturb on the other hand)
the following conclusions can be made for
the SF6 circuit breaker model:
Dissertations
Using SF6 as filling and quenching gas in
self-blast circuit breakers the resistance at
the stagnation point is approximately as
high as the results in the nozzles. Thus,
the total resistance is determined by these
two areas. The main cooling mechanism at
the stagnation point is dominated by convective cooling effects. In the nozzles the
turbulent cooling is the main cooling mechanism. Hence, both cooling mechanism are
important for the generation of the total resistance. If CO2 is used as the filling gas in
the circuit breaker model the resistance is
mainly generated in the area of the stagnation point. Thus, the convective cooling is
the dominant cooling mechanism for CO2
circuit breakers. Nevertheless, the total resistance of the CO2 circuit breaker model is
lower than the value of the SF6 one. Hence,
the switching performance of SF6 gas is
better than of CO2. A more detailed presentation and discussion of the investigations
are described in [2].
Summary
The thesis gives a more detailed insight
of the physical processes during the current zero phases of gas filled circuit breakers. Further, the analysis of the spatial resolved resistance distribution gives a better understanding of the resistance development and accordingly the dominant cooling
Using the CO2 circuit breaker model the
following relationships can be determined:
effects for the arc quenching. Depending
on the switching arc area two different cooling mechanisms can be effective. The convective cooling occurs mainly at the area
around the stagnation point whereas the turbulent cooling is the main effect within the
nozzles. The intensity of cooling and thus
the amount of the resistance development is
depending on the quenching gas of the circuit breaker. In SF6 circuit breakers both
cooling mechanism are relevant to generate
an arc resistance. For a CO2 circuit breaker
the convective cooling is the dominant effect. Hence, design and optimization criteria need to be developed for the two gases
individually.
References
[1] C. Kahlen, R. Dommerque, M.
Schwinne, M.-C. Tang, A. Schnettler: Application of a New Measuring System for Investigations of
the Interruption Behaviour of a
SF6-Selfblast Circuit Breaker Model,
XVIth Symposium on Physics of
Switching Arc, Brno, 2005
[2] M.-C. Tang: Widerstandsverteilung
in Schaltlichtbögen von Selbstblasleistungsschaltern während der
Stromnulldurchgangsphase, Dissertation RWTH Aachen, Schriftenreihe:
Aachener Beiträge zur
Hochspannungstechnik, Band 13,
ISBN 3-86130-676-X, 2010
Contact
Dr. Ming Chark Tang
[email protected]
+49 221 676-2003
77
78
HumTec
Modelling of the future energy supply structure
HumTec is an interdisciplinary project house of the RWTH Aachen University, which is built
up in the frame of the German excellence initiative. The project house has the aim to advance the interdisciplinary work between the humanities, natural- and engineering science.
The Institute for high voltage technology (IFHT) provides together with the Thermal Process
Engineering the engineering competences in our work group Ethics for Energy Technology
(EET). The models are developed with computer scientists and mechanical engineers.
Description of the project
The main focus of the project is the development of an integrated assessment model,
which contains different modules. The
model enfolds a global point of view and
has its final date in the year 2100. This
model is able to built up connections between the development of the population,
consumption of resources, energy supply,
use of land areas, climate and the economy, whereby every research group has its
own part and focus. One aim is to analyse the political influence on the different
model parts. With the help of the model
various scenarios for the future energy mix
are calculated. The paths are based and optimized on the present data and prognoses
for costs. In addition there are limits for
technologies and other constraints. As consequence of the increasing world population, higher living standards and the shortage of fossil fuels questions of the future
energy supply and demand become more
important in social and political decisions.
For this reason the energy model considers especially the development of the markets for fossil fuels. The global resource
model should evaluate the production paths
and price evolution for crude oil, natural
gas and coal. The allocation of the resources is optimized with economical criteria, that means that the total cost for the
extraction of each resource are minimized.
The distribution of the resources is consid-
ered on a global level, whereas the world
is divided into six world regions, so called
agents. The agents represent and interact
not only as the supplier but also as the consumer for each region on this macro level.
Before starting modelling the most relevant
influence factors are filtered and analysed.
This includes the possibility of substitution
between the fossil and the reneweable fuels and the transformation and integration
of technological progress into the model.
Because of the shortage of fossil fuels the
reneweable energies, such as wind, solar
and biomass energy, will become more and
more important. The final time of modelling in the year 2100 underlines this aspect. The consideration of social and political factors influences more and more the
development in the frame of the energy supply. For this reason these aspects have to
be examined and taken into account. Exemplary are shown two research activities.
On the one side „DESERTEC“, in which
the electricity of north african solar energy
plants should support the energy supply of
Europe and other side the new technology
„Carbon Capture and Storage“ (CCS). This
technology is able to capture the carbon
dioxide from the power generation process.
After that the captured carbon dioxid is
transported to a suitable storage. Technical
solutions need connection and interaction
of social questions to the known economical and technical ones, what is especially
HumTec
of the exported electricity and develop their
countries and so the whole african continent. Despite to all aspects the danger
of Europe’s reliance on North African solar electricity, compared with one, as currently from the oil-producing countries, has
to be excluded. For this reason, in a holistic assessment, the different open questions
regarding energy security, socio-economic
development and international cooperation
have to be clarified to ensure the long-term
success of the project „DESERTEC“.
Another development, which is a typical example for the interface of the work of EET,
is CCS. Besides the necessary economical
and technical considerations of the technology there are also expected problems relating its acceptance and penetration. The
mass media and the people need answers
for the open questions especially for the
storage of the carbon dioxide, so that the
power supply companies first have to convince the people and need the legal conditions for the realization of CCS.
These examples impressively show that the
future energy mix is not only influenced by
economical, ecological and technical criteria, but also by social and political ones.
References
[1] DLR, Strom aus der Wüste,
Deutsches Zentrum für Luft- und
Raumfahrt, 2010
Contact
Dipl.-Wirt.-Ing. Baris Özalay
[email protected]
+49 241 80-93041
shown by the open and discussed questions
in the project „DESERTEC“. This project
has the aim to realize the high potential of
solar energy in the region of north africa,
to meet the increasing electricity demand of
Europe. The electricity transport to europe
should be realized by an HVDC system and
produce 15 percent of the european electricity in 2050 [1].
There are basically four different possibilities to install electrical lines from North
Africa to Europe. One way leads from
morocco through the street of Gibraltar to
Spain, a second one goes from Tunisia
through Sicilia to Italy. The third possibility is the long sea way from Libya to
Greece and the last one is described by the
terrain connection about the Middle East
and Turkey . A single two-point HVDC
link from Egyptian up to the load center
in Central Europe would cover a distance
of about 4000 km and that is why it will
not be the first route to be built. The connection to Greece is also unlikely as the
first line path, because the sea connection
is with 500 km very long. Realistically,
HVDC links with multiple entry points on
the way from North Africa to the load centers will be in central Europe, especially
Germany and France. Thus, the electrical
energy on their way to the heart of Europe
can be distributed from various points. A
country would not approve the building of
a high-power transmission line without it
even to be connected and participate with
the use of the electrical energy. As connection points are load centers suitable, primarily nodes near large cities. Next to
such technical and economical considerations also social factors influence the development of the project. The affected African
countries could benefit from the revenues
79
80
Teaching at IFHT
81
82
Introduction of Bachelor and
Courses in Electrical Engineering
Master-
With the winter term 2007/2008 the Bachelor of Science (B.Sc.) in electrical engineering
was introduced at RWTH Aachen university and replaced the former Diploma-degree. Winter term 2010/2011 brought the introduction of the consecutive Master of Science (M.Sc.).
Together with this changes, content and structures of the study programmes were reevaluated and improved. There also have been changes for the IFHT.
New Lectures and changed contents
Due to the change to the new Bachelor and
Master degrees an adaptation of content
and structure of the teaching in all institutes of the faculty was necessary. Now
all courses are modularized and listed in a
module handbook. For the specialization of
power engineering in the Master degree the
IFHT coordinated the compilation of this
handbook. Moreover, the range of courses
tought at the IFHT was adapted as shown
in the following.
Components and Installations for the
Supply of Electricity
The lecture Components and Installations
for the Supply of Electricity is compulsory
for 5th semester bachelor students specializing in power engineering. It was introduced in the winter term 2009/2010. Prof.
Schnettler and Prof. Hameyer from the Institute for Electrical Machines (IEM) teach
the lecture together. With the topics wind,
hydro and steam power-plants as well as
generators and transformers Prof. Hameyer
is focussing on the generation of electricty.
Prof. Schnettler is focussing on the components of the grid, such as overhead lines,
switchgear, surge arresters, measurement
devices and test circuits.
For the compilation of the lecture (including script and powerpoint slides) both institutes were granted funds from study fees.
With over 100 students the lecture was very
well attended which shows that among the
students the power engineering specializa-
tion is very popular.
High Voltage Engineering
In the diploma study programme the lecture High Voltage Engineering was divided
into two consecutive parts. This had to be
changed for the Master study programme as
the students have, due to practical semester
and thesis semester, only two semesters left
for attending lectures. Therefore, greater
flexibility had to be made possible. To
achieve this, content and title of the two
lectures have been adapted in a way that
enables the students to visit the lectures
High Voltage Engineering - Insulation Systems and High Voltage Engineering - Test
Systems and Diagnosis and take the respective exams independently. Until now, the
content of the latter has been reevalued and
changed and is presented with a completely
new set of powerpoint slides.
For this adaption the institute was granted
fund from study fees as well.
New Seminars and Projects
Also the range of projects and seminars offered at IFHT has been adapted to the new
courses’ requirements.
Seminar Energy Supply in the Future
The former seminar Technology of Gas
Discharges has been replaced by the new
seminar Energy Supply in the Future. Participants have to present topics on relevant
future developments in Power Engineering.
The seminar is open to Bachelor and Mas-
Teaching
their supervising tutors for help and advice.
Fig. 1: The fastest car
Highlight of the project was a time trial
in which the cars of the student groups
raced each other and the car of the supervisors. The cars had to fulfill all safety requirements and drive the race course at least
two consecutive times. Picture 1 shows the
winning team’s car. The participants enjoyed the project and it is planned to repeat
it in the coming years.
ter students. Bachelor students are awarded
3 CP for participation and a ten minutes presentation. Master students have the opportunity to gain 4 CP by handing in an additional three to five page paper.
4th Semester Project
In summer term 2010 the faculty’s institutes
for power engineering (IFHT, ISEA, IAEW,
IEM, ACS) together offered a project for
4th semester students. In groups of three
the participants built a roadworthy electric model car. To achieve this they had
to learn about batteries, DC-motors for
the drive, DC-DC-converters, servomotors
for the steering and the required measurement and control systems. As the car had
to drive a racetrack independently a special attention had to be given to the control and protection to avoid damage and
provide security. The basis was a construction kit that was the same for all student groups. The students had to design and built the circuit boards, assemble the cars and program the control software. In five units they were given the
necessary background information on track
and speed sensors, DC-DC-converter, motors and programming of the micro controller. Moreover, they always could ask
83
Contact
Dipl.-Gwl. Maximilian Keller
[email protected]
+49 241 80-94924
Teaching at IFHT
High Voltage Engineering Insulation Systems (Summer
term)
Components and Installations
for the Supply of Electricity
(Winter Term)
Lecturer: Prof. Dr.-Ing. A. Schnettler
L2/E1, from 6th semester, International
Master Program: 2nd semester
German and English
Lecturer:
Content
• Overvoltages in power systems:
Travelling waves, overvoltage protection
• Breakdown-phenomena: Statistics,
breakdown in gases, solids and liquids, vacuum breakdown, arcing,
pollution flashover
84
Prof. Dr.-Ing. A. Schnettler
Prof. Dr.-Ing. habil. Dr. h.c.
K. Hameyer
L2/E1, from 5th Semester
Bachelor
German only
Content
This lecture is offered in collaboration with
the Institute for Electrical Machines (IEM).
• Introduction to electrical power engineering
• Insulation systems and dielectrics
• Electric field
• Technical excursion
• Gas discharge technology
High Voltage Engineering Test Systems and Diagnosis
(Winter Term)
Lecturer: Prof. Dr.-Ing. A. Schnettler
L2/E1, from 7th semester, International
Master Program: 3rd semester
German and English
Content
• Generation and measurement of high
AC, DC and impulse voltages
• Dividers and Shunts
• High voltage equipment: Construction, capacitors, bushing, transformers, breakers
• Electromagnetic
compatibility
(EMC) for power systems
• Introduction to the most important
components for the supply of electricity
• Testing of equipment
Protective
Measures
and
Equipment in Power Supply
Systems and Electrical Installations
Lecturer: Dr.-Ing. B. Thies
L2/E1, Master program in Electrical
Power Engineering
German and English
Content
• Regulations and standards, national,
regional and world-wide safety regulations and standards, legal authority
of standardisation, test certificates
Teaching
Power Cable
(Winter Term)
• Protective measures of low voltage installations against direct and
indirect contact, configurations of
the network, safety, protectional and
functional extra low voltage, evaluation
Content
Engineering
Lecturer: Dr.-Ing. D. Meurer
L2/E1, Master program in Electrical Power
Engineering
English only
• Introduction: cable industry, cable
market, power cables in networks,
history, technical standards, transmission properties
• Cable Components: materials, conductor, insulation, screen, sheath, armour
• Protective measures of high voltage
installations, earthing, overvoltage
and lightning protection
• Protection of lines and cables against
overload and short circuits
• Design: low-/medium-/high-voltage
cables, utility/special cables
• Production: paper insulated/extruded
cables, conductor/core/cable
• Quality Management: ISO 9000,
quality assurance, type-/sample/routine-test, commissioning test,
ageing, lifetime
• Accessories: termination, joints,
field control, installation techniques
• Protective equipments and their
modes of action, protection criteria,
fuses, line protective switches and
current-operated earth-leakage circuit breakers, relays, surge arresters
• Protection systems for motors, generators and transformers
• Risk of electric currents, accident
statistics, effects of current on human body, safety limits, endangering
by high-frequency fields
• Cable Projects: cable route, current
carrying capacity, transport, laying
• High Power Cables: cable losses,
forced cooling,
HVDC, gasinsulated cables, cryogenic cables, superconducting cables (LTSC,
HTSC)
Seminar
Switchgear
and
Substations (Summer/Winter
Term)
Lecturer (Summer term): Prof. Dr.-Ing. A.
Schnettler, Dr.-Ing. M. Schumacher (ABB
AG), together with partners from the industry
85
Lecturer (Winter term): Prof. Dr.-Ing. A.
Schnettler, Dr.-Ing. R. Puffer
5th Semester Bachelor German only
• Grids and components
• Overland lines
Content
• Switching arcs
• Components: masts, armatures etc
• Construction
• SF6 circuit breaker
• Operation
• Vacuum circuit breaker
• Maintenance
• High voltage fuses
• Conductors
• HVDC
• Air insulated substations
• Gas insulated substations
• Medium voltage switchgear and substations
• Power transformers
• Cables and overhead lines
86
Contents
• Asset management in distribution
grids
Business Managment for Engineers (Summer Term)
Lecturer: Dr.-Ing. J. Schneider
L2, E1
German only
Content
• Company structures
• Business administration
• Finnace
Compare report on page 107
• General Management:
Strategic
planning, budget, controlling
Overhead lines (Winter term)
• Project management: Risk analysis, cost planning, marketing, quality
management, Corporate Governance
Lecturer: Dr.-Ing. R. Puffer
L2, E1, ab 5. Semester
German only
• Optimization
Teaching
Laboratory in Electrical Power
Engineering I
(Summer Term)
TE4, from 6th Semester
German and English
Electrotechnical Laboratory I
(Summer term)
TE3, from 2nd Semester
German only
Content
Content
The laboratory in Electrical Power Engineering I is carried out by several institutes.
Three experiments take place at the Institute
for High Voltage Engineering:
The Lab contains 8 basic units:
• Current- und voltage sources
• Voltage divider
• Measurement in linear circuits
• Measurement of alternating voltages
/ Breakdown measurements
• Simulation of linear circuits
• Generation and measurement of direct voltages
• OP Amp (Measurement)
• Surge voltages
• Measurement of non-elctrical phenomena
Laboratory in Electrical Power
Engineering II
(Winter Term)
German and English
• Diode und transistor
• OP Amp (Simulation)
High Voltage Laboratory
German only
Content
• Breakdown measurements
Content
The laboratory in Electrical Power Engineering II is carried out by several institutes. Three experiments take place at the
Institute for High Voltage Engineering
• High Voltage Divider
Laboratory Courses at IFHT
• Experiment on DC voltage
• Partial discharge
• EMC Interference Launch
• Surge voltages
• Transient processes on wires
• Transient Processes on Wires, Travelling Waves
• High voltage divider
• Electromagnetic Coupling
• Dimensioning of a synthetic test circuit
87
Measurement Laboratory for
Mechanical Engineers
(SS)
4th
TE4, from
Semester
Collaboration of the faculties for electrical
engineering, mechanical engineering and
science and methmatics
German only
88
Content
The IFHT offers 4 labs in this course:
1. Voltage source and transformer
2. Measurement of electrical phenomena
3. Oscilloscope and rectifiers
4. Digital measurements
Theses
Diploma Theses
Altwasser, Dominik
Entwicklung optimaler Managementstrategien für Elektrofahrzeuge
Both the continuing climate change and increasing instability of commodity markets
have ignited a social and political debate
over Germany’s future mobility strategy, of
which one of the most widely and publicly
recognized core elements is electromobility. At this juncture, the integration of electric vehicles into the existing transmission
and distribution network constitutes a focal
point of recent research in this area. Part
of this interest may arise from the ability
of electric vehicles to store energy temporarily before it is used later to generate
mechanical operating energy, allowing for
the flexible control of charging and discharging. In this thesis, a control procedure
based on evolutionary algorithms was developed with the aim of exploring the possibilities of flexible charging and discharging. Using these algorithms, both the temporal and spatial arrangement of the charging processes can be selectively modified
according to various criteria in a real network model. Possible applications of this
procedure include avoiding overloading the
existing network infrastructure as well as
charging the observed electric vehicles at
the lowest possible cost. The functionality of the devised procedure was verified in
the course of this thesis by applying it to a
developed scenario; as expected, the algorithm arranged the charging processes corresponding to the specified goal function.
Anomalies that were observed, especially
relating to the spatial component of the op-
timization procedure, could be ascribed to
the nature of the vehicle population under
consideration. Finally, consequent analyses
showed the potential of evolutionary algorithms for additional uses, such as multicriteria optimizations and the application
of probabilistic dependent and target variables.
Betreuer: Thomas Pollok, M.Sc., Dipl.-Ing.
Thomas Helmschrott
Diploma, Master, Bachelor and Study Theses completed in 2010
Beilin, Michael
Investigation on the Impact of Nanofiller
on the Properties of Syntactic Foam
Syntactic foam is a composite material consisting of hollow glass microspheres and
epoxy resin, which is used as a lightweight
insulation material for high voltage applications. The viscosity of epoxy resin is
increased by inserting microspheres. This
results in a maximum filling degree, which
is currently reached at 55 vol.-%. The viscosity can be lowered by adding nanoscaled
particles - so called nanofillers - to the composite. The focus of this diploma thesis lays
on the experimental and theoretical investigation of the thermal, electrical and mechanical properties of syntactic foam with
nanofiller. Based on the gained knowledge different models are created to explain the impact of nanofiller on the properties of syntactic foam. As main result of
this thesis an improvement of the electrical
and thermal properties by the influence of
nanofillers can be ascertained. On the other
hand the mechanical properties are slightly
declined.
Supervisor: Dipl.-Ing. Anja Strauchs,
89
90
Doroudian, Sepideh
Szenarioanalyse zur Bestimmung des Einflusses fluktuierender Einspeisung auf die
deutschen Stromnetze
This thesis analyses the impact of the integration of decentralised energy conversion
technologies and the subsequent fluctuation of load and supply on low voltage
power grids. Due to political objectives
and a growing ecologic consciousness of
society an increasing level of the use of decentralised energy conversion technologies
grids is expected in the incoming years. In
order to examine the Impact of these Technologies on the low voltage power grids at
first a simulation model is developed. This
model simulates the stochastic behaviour
of single decentralised energy conversion
technologies. Using this model, the potential for each of the individual conversion
technologies is determined. This is done
both for the present state and - by means
of a scenario analysis - for possible future
developments until the year 2040. Subsequently, the specific costs and emissions as
well as the self-sufficiency of the grid area
are calculated for selected scenarios. The
results of these calculations make it possible to draw conclusions on the optimal
network operation and on a necessary future development of the portfolio of power
plants.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Thomas Dederichs, Dipl.-Wirt.-Ing. Eva
Szczechowicz
Dulisch, Fabian
Conception, enhancement and implementation of a test circuit to investigate contact
materials in vacuum switching chambers
During the last 30 years the vacuum switching technology was established for low and
medium voltage applications up to 40.5 kV
with increasing market share asserting its
position opposite to other switching tech-
nologies as minimum-oil or SF6 circuit
breakers. Due to application of modern
contact materials and contact geometries
vacuum switching chambers are suitable
for almost all switching operations. The
durability of vacuum switching chambers
is significantly determined by the used contact material. Therefore in the context of
this diploma thesis a test circuit, which emulates duty with a high number of switching
operations, is conceived, enhanced and operated. Furthermore different contact materials are investigated.
Supervisor: Dipl.-Ing. Andreas Kurz, Dr.
D. Gentsch
Filippidis, Stylianos
Condition detection and prognosis of equipments inside air-insulated substations
The maintenance of the components in the
electrical network has a direct influence on
the costs and quality of supply. A detection
of the condition as well as a condition prognosis allow network operators to achieve
a condition-based maintenance, which is
seen as cost-effective. A method for condition detection and prognosis was developed
in this work, which considers the knowledge of the experts in house of the network
operators.
Supervisor: Dipl.-Ing. Christian Hille
Fuchs, Bernhard
Experimentelle Analyse der Stromtragfähigkeit elektrischer Freileitungen
For a number of reasons, such as the liberalisation of the energy market, the eastern
expansion of the UCTE - grid or the development of windenergy-engineering, the
demands on the german transmission grids
have changed. The grids should be reconstructed to fulfill the new requirements of
power flows in the future. In reality these
methods require long licensing procedures
(usually >10 years), therefore it is necessary
Theses
Gialinizoglou, Vasileios
Entwurf und Aufbau eines Kommunikationssystems zur Anbindung dezentraler
Messsysteme und steuerbarer Lasten an
eine Leitstelle
The phenomenon Climate Changerepresents one of the greatest challenges of our
time. Meanwhile Climate Protection demands a dramatic reduction of emissions
and thus the shift of the current energy system towards a more efficient one providing
moresources of renewable energy. Politics
recently have understood that it is the interest ofwhole mankind that certain steps have
to be undertaken. Climate Protection has
beenidentified as the predominant force for
generating economic growth and employment. It is the contribution of this degree
dissertation to assist in restricting Climate
Changeby providing a better network inte-
gration of renewable energies into the established infrastructures. By this diploma
thesis three systems have been developed
including a measuring, a communication as
well as a data logging system. These systems have been built up and implemented in
order to function as the spine of a monitoring system for the surveillance of the network condition. The DIN EN 50160 serves
as the basis for the identification of relevant
parameters for the description of the network condition. Furthermore - grounded
on the measuring method according to DIN
EN 61000-4-30 - the implementation of the
measuring data registration has been done.
As a result all forthcomingly registrated
and calculated data will be stored in a data
bank within a capable structure where it
will be at hand for all coming scientific research. First measurings have shown that
the erected measuring system works well
and that the measured data has been successfully transmitted over the virtual private network (communication system) and
stored in the data base. Concerning the network throughput the performance analysis
has shown good results (average network
throughput 6 kbit/sec ), while the processor
usage proved alarming and worth of improval.
Betreuer: Dipl.-Ing. Claas Matrose, Dipl.Ing. Holger Krings
Gödde, Markus
Technische
Analyse
des Einflusses
verteilter Energiewandlungseinheiten auf
Verteilungsnetze mithilfe eines agentenbasierten Investitionsmodells
The thesis at hand deals with technical,
economic and ecological consequences of
an increased integration of distributed energy conversion units on distribution grid
infrastructure. The Core of the work is
an agent-based investment decision model,
that simulates the decision making process
of households on energy conversion units
to look for alternative solutions til then. For
these reasons the monitoring of overhead
lines plays an important role. The idea is to
take advantage of the present weather conditions in order to increase the ampacity of
existing overhead lines. Therefore models
are used, which describe the thermal behavior of overhead conductors subject to
different weather conditions. Using the CIGRE model, a validation should be made by
means of experimential investigations. This
thesis focuses on constructing a laboratory,
in order to investigate the impact of low
wind speeds (< 1m/s) on conductor temperature. The construction is based on the
analyses of the existing technical requirements and the sensitivity of the physical
model. After the description of realisation
the breadboarding will be calibrated and
analysed. Last but not least, measurements
will be carried out in order to analyse the
validation of the model.
Betreuer: Dipl.-Ing. Martin Scheufen,
Dipl.-Ing. Dipl.-Wirt.Ing. Thomas Dederichs
91
92
for the example of photovoltaic, microcombined heat and power and small wind
turbine units taking into account socioeconomic factors. Under consideration of
weather and geographical data the model
provides penetration rates for different
types of areas until 2030. In addition,
electric vehicles are considered as an exogenous factor. On this basis load flow
calculations are performed for different distribution systems and the effectiveness of
control mechanisms through intelligent local network stations, charging strategies of
electric vehicles and interference in the subsidization of energy conversion units were
analyzed. Furthermore, a method is presented by which the combination of agent
populations and distribution networks can
be evaluated for various support strategies
and calculatory areas in terms of the specific CO2 emissions (ecologically), subsidies and network expansion costs (economically), and voltage ligament injuries and
self-sufficiency (technically) over time until
2030. One result of this work is the heavy
stress of distribution networks in rural and
sunny areas in southern Germany by the
increasing number of photovoltaic installations, leading to locally high grid development costs and relatively low levels of
self-sufficiency. In the model, a higher subsidy for combined heat and power and small
wind turbines in the context of the technical ecoefficiency leads to better results. It is
also noted that intelligent local network stations can significantly contribute to network
stability, but can only delay necessary grid
development costs minimally. With a moderate penetration of electric vehicles with
a small power input the network stability
cannot be significantly increased. Overall,
it is found that the increased penetration
of distributed energy conversion units leads
to high supplies of electric energy into the
transmission grid infrastructure, especially
during summer in southern, populous areas. This will significantly affect the power
plant scheduling in the future.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Szczechowicz
Güthe, Alexander Thomas
Ökologisch-technische Analyse von Betriebsstrategien für Elektrofahrzeuge zur
Integration von erneuerbaren Energien ins
Übertragungsnetz
Through voluntary commitment, such as
the Kyoto Protocol, increasing pressure is
noticeable in regard to avoid emissions.
The objectives of the policy are ambitious
and can only be realized with great effort.
A significant contribution to achieve these
aims could be the integration of new concepts, such as electric vehicles and renewable energy. Because of the ecological
potentials of electric vehicles as well as
plug-in hybrids these are investigated in the
present work. Two possibilities to foster the
reduction of the emissions are highlighted the lowering of direct vehicle emissions as
well as supporting the integration of renewable energies. For this, appropriate loading
strategies are developed and implemented
using a simulation model. A distinction
of six categories of vehicle permits a both
precise and differentiated determination of
vehicle emissions, allowing a comparison
with conventional vehicles which goes beyond the ordinary averaging. As a rating the
CO2 equivalent is used. The results show
a clear environmental advantage of electric
vehicles over their counterparts with combustion engine. It also shows that the limits
of possible support of the integration of renewable energies such as centrally bundled
offshore wind farms through electric vehicles are quickly reached.
Betreuer: Dipl.-Wirt.-Ing. Eva Szczechowicz, Dipl.-Ing. Dipl.-Wirt.Ing. Thomas
Dederichs
Theses
Szenarienbasierte Bewertung der Entwicklung von Elektromobilität unter Berücksichtigung netztechnischer und wirtschaftlicher
Aspekte
The focus of this thesis is on the implications of charging infrastructure for electro mobility. Infrastructure is admittedly
a crucial aspect for the future technological diffusion of electric cars into the mass
market, due to the very limited user willingness of driving an electric car without
the opportunity of public charging. None
the less, critical aspects regarding the business, economic and ecologic implications
are not elaborated yet. In the end, the future charging infrastructure will be defined
by the future electric fleet. As well, only
limited insights are given in the framework
of the future fleet development. Within this
thesis an approach is developed that - based
on real life motorized journeys - is able to
extrapolate future trends within the fleet
population by using a multi-agent-system.
Based on the penetration of electric cars,
policy advices are given concerning subsidies strategies for charging infrastructure.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Thomas Dederichs, Dipl.-Ing. Claas Matrose, Dipl.-Kfm. Andreas Pfeiffer
Kalverkamp, Frederik
Bewertung der elektrischen Eigenschaften
von Windparks auf Basis von Modellrechnungen mit Blick auf die Vorgaben der Systemdienstleistungsverordnung
The present study deals with the evaluation
of electrical properties of power generation systems. Its verification at the point
of common coupling is required by The
Ancillary Service Directive (SDLWindV)
since 2009. Corresponding references are
based on an authentic wind farm. At first
the underlying grid codes are presented
as well as the effective technical guide-
lines of the german research association
for wind power and renewable energies,
FGW. Moreover the methods to be applied
and the arithmetic techniques for the validation of simulation models are explained,
which represent the basis for the dynamic
behavior of wind farms during grid faults.
Furthermore the methodology for evaluation of electrical properties of power generation systems based on these simulation
models and further characteristics of wind
turbines and additional equipment of the
wind farm is identified and demonstrated.
The examination of the validation criteria
using a concrete manufacturer model of a
real wind turbine leads to a validated simulation model to portray the behavior of
the whole power generation system during a grid fault. These dynamic stability
analyses and additional calculations of the
electrical properties of the wind farm - using power flow calculations and approved
calculation methods - as well as the verification of certificates of wind turbines and
characteristics of further components constitute the basis of the evaluation in terms
of its conformity to standards. In addition
further technical analyses of different net
conditions and -topologies are realized and
subsequent evaluations concerning the system stability accomplished. These technical
studies are followed by a monetary evaluation of the ancillary service for the grid
that has been demonstrated and an effortbenefit-assessment of the steps in process
validation and system simulation. The work
closes with an outlook of additional open
issues in the determined certification approach.
Betreuer: Dipl.-Ing. Martin Brennecke,
Dipl.-Phys. Bernhard Schowe-von der Brelie, Dipl.-Ing. Dipl.-Wirt.Ing. Thomas
Dederichs
Kippen, Michael
Monetary network evaluation based on free
Hinrichs, Hauke
93
available information
The worldwide increasing energy market
liberalization offers the possibility of network acquisition and sale to network operators. A previous monetary evaluation of the
networks is a mandatory requisite for purchasers to judge and estimate the purchase
amount. In this work, a method for value
estimation of high and highest voltage networks has to be developed based on free
available information. For this, it was essential to determine the number of installed
cost-intensive equipments. An innovative
procedure has been developed and can be
found in the current annual report under
the topic Synthetic generation of network
topologies based on the use of free available data.
Klosta, Florian
94
Modellierung und Analyse von virtuellen
Energieversorgungssystemen mit verteilten
Wandlungseinheiten
This thesis researches the supply of an investigation area with power and heat. The
chosen approach to the topic is a Virtual
Energy Supply System with centralized
control consisting of the interconnection of
dispersed energy conversion, load, storage
and net to guarantee an economic, ecologic
and save supply with power and heating in
the private sector. The base of the developed model of the Virtual Energy Supply
System is the analysis of the requested heat
and the conversion units for the thermal and
electrical feed-in. The model is capable to
simulate and evaluate differently composed
electrical and thermal conversion unit parks
and integrated strategies. The results show
that the interconnection to a Virtual Energy
Supply System provides economic and ecologic advantages in comparison with the
uncontrolled supply with power and heat.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Thomas Dederichs, Dipl.-Ing. Stefan Krengel, Dipl.-Ing. Joachim Funcke (IDG)
Koch, Myriam
Investigation of the measurement of arc resistance distribution depending on position
The electric arc inside high voltage circuit breakers is surrounded by a nozzle and
cooled by a quenching gas flow. This gas
flow leads to an increase of arc resistance
close to the natural current zero crossing.
A successful interruption of the current is
strongly depending on the increasing arc
resistance. Present investigations show not
only a strong influence of the total arc resistance but of the spatial distribution on
the interruption capability. For investigating this spatial arc resistance distribution over time a new measuring system is
developed and established at the Institute
for High Voltage Technology. The present
diploma thesis performs basic investigations to achieve important characteristics
and parameters for dimensioning this new
measuring system.
Supervisor: Dipl.-Ing. Matthias Hoffacker
Lütcke-Lengerich, Christoph
Analyse von Umwelteinflüssen auf die
Stromtragfähigkeit elektrischer Freileitungen (Freileitungs-Monitoring)
mittels
charakteristischer Betriebs- und Geodaten
Due to the increasing supply of renewable
energies in the German high-voltage grid,
especially speaking of the more dominating wind energy supply in the north the
existing overhead lines come up against
their limiting factors. Using overhead line
monitoring it is possible to increase the carrying capacity of the overhead line using
weather-related cooling effects. To calculate the higher current carrying capacity the
Cigré-Model is taken as a basis. Refering
to this the influence of the wind speed has
the greatest cooling effect. Therefore, in
Theses
Ma, Ming
Analyse und Modellierung der Ausgestaltung zukünftiger Marktplätze für energiebezogene Systemdienstleistungen
In the present work the control energy market design is investigated in the future to
support the rapid integration of renewable
energy. The economic and technical influences are evaluated for the modeling of
these designs to market. To the provision
of ancillary services in the area frequency
control (such as the provision of control energy/power) lead the four transmission system operator by the tender on the common
Internet-platform to meet their own needs
of the control power. This auction mechanism is the current German control power
market. This model is faced with the challenge to adapt to future situations and to
guarantee the security system ever. For the
economic analysis are the criteria of minimizing costs and reducing the burden of
consumers in the center of events. The aim
of the developed market model is to create
scenarios of the future market design, to examine procurement costs and profitability
of the power plant operators in compliance
with technical constraints. In the context
of the scenario analysis, the factors influencing the control power consumption and
price trends are analyzed for the control energy market. The control power demand for
2020 is determined using the first model for
different scenarios and view both values of
the Economy can be determined using the
market model for the scenarios of market
design. After examining the results in particular future trading opportunities of the
control energy market is recommended.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Szczechowicz
this work a method for spatial interpolation
of wind speed has been implemented taking shadowing effects of the landscape into
account. Using this method, the higher capacity of an exemplary power transmission
line was represented on a potential map.
This is continued by a bottleneck analysis
of transmission line, which helps the transmission system operator to decide where
weather measurement technology should
be installed. The final evaluation based on
a synthetic network shows that by using the
overhead line monitoring at the found locations is possibility to increase the capacity
of overhead lines on the basis of the implemented procedure.
Meinerzhagen, Ann-Kathrin
Szenarioanalyse zur technischen Ökoeffizienzbewertung globaler Energieversorgung
This thesis deals with an analysis of influences of global energy supply and potential
assessment criteria. To this end, scenario
analysis is introduced as the chosen approach. A survey of different methods for
evaluating the technical eco-efficiency of
the global energy supply and an analysis of
the current supply situation form the ground
of the scenario analysis. First, global causal
chains that affect the energy supply composition are identified by reviewing models of
economic, social and ecological processes.
Further influences are determined through
an appraisal of known scenarios. Based on
the findings from these first steps, drivers
of the global energy supply are defined and
their interconnected dependencies are explicated. Founded on this knowledge, a
model of worldwide energy usage is developed. A sensitivity analysis of the model
gives further insight into the interactions
that rule global energy demand. Thus, scenarios for a further assessment of worldwide energy supply are elaborated and criteria for a technical eco-efficiency assess-
95
96
ment are devised.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Thomas Dederichs, Prof. Dr. Dr. Rafaela
Hillerbrand
Natemeyer, Hendrik
Szenarioanalyse zur ganzheitlichen Bewertung zukünftiger Ausbaumaßnahmen im
europäischen Übertragungsnetz
The intensive promotion of renewable
power generation and the demand for the
expansion of the European power trading
necessitate the development of the European transmission grid. To create this development ideal, a tool for assessing predefined extension measures becomes necessary. This tool will be developed in this
study. Therefore, a model of the grid and
a power plant database are developed and
assembled into a complete model of the
European electricity supply. To calculate
this model, the methodology of the OPF
(Optimal Power Flow) is used. In addition, this is extended with respect to an
ecological approach (Ecological OPF). The
methodology of the OPF is explained and
validated in comparison to a simulation of
the power plant scheduling. On the basis of
planning principles in the transmission grid,
economical, ecological and technical criteria are created that allow an assessment of
development measures. To represent various loads of the grid, scenarios are defined that represent the different situations
of electricity demand and the availability of
renewable energy sources. Finally, development measures in the European transmission grid are identified fromexternal
sources and evaluated in terms of economical, ecological and technical criteria.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Thomas Dederichs, Dipl.-Ing.
Martin
Scheufen
Neef, Florian
Entwicklung und Modellierung netzstabilisierender Maßnahmen für Elektrofahrzeuge im Verbundnetz
Within this thesis a reduced grid model is
developed, which allows to qualitatively investigate the influence of power conversion
units on the stability of the European interconnected power system. Electric vehicles with energy storage systems and plugin capability are examined exemplarily for
power conversion units. The examination
of stability includes aspects of small-signalstability as well as those of transient stability. A restriction is made by considering the mains frequency as the important factor and neglecting the system voltage. Small-signal-stability is investigated
by modal analysis and transient stability by
RMS-simulations. The effects of different
regulation concepts on the energy supply
of electric vehicles and its impact on the
damping of critical inter-area-oscillations
is analyzed. With the help of the developed
model it can be shown that the damping of
inter-area-oscillations improves by increasing the quantity of adequately controlled
electric vehicles. Also the fall off of mains
frequency after power plant failures can be
attenuated. Nowadays it is not permitted to
participate with the electric vehicles in the
primary control market, in spite of the technical feasibility. Therefore a reorganization
of the statutory framework is recommended
to guarantee the grid stability for the future,
as a further reduction of rotating mass is
forecasted.
Betreuer: Thomas Pollok, M.Sc., Dipl.Wirt.-Ing. Eva Szczechowicz
Nikolic, Gregor
Investigation and modelling of the dielectric strength for hot gases in insulating nozzles
Nowadays sulphur hexafluoride SF6 is used
in high voltage circuit breakers due to its
outstanding dielectric and arc quenching
Theses
Plath, Cornelius
Condition assessment of power supply
equipments
This diploma thesis investigated which established possibilities could be applied to
assess the condition of equipments. For
this it is possible to employ historical data,
as well as the knowledge of manufacturers
and the experience of network operators.
An appropriate possibility has been implemented and verified by means of an available database. Lastly, possible economical
scenarios of the condition were sketched in
order to introduce the results of this work
into a network evaluation.
Roder, Jochen
Spannungsebenenübergreifende Bewertung
von Verteilungsnetzen unter Berücksichtigung von Elektromobilität
In recent theses at the IFHT the effect of
rising penetration by electric vehicles on
single voltage levels of distribution grids
has been investigated using powerflow calculations. Furthermore different charging
strategies for electric vehicles have been developed and evaluated on low-voltage grids.
Based on the already developed methods
the coupling of the voltage-levels is involved in this thesis for the first time. The
analysis of distribution grids is expanded
to the detection of weak spots for directed
grid enforcement and to the consideration
of redundancy concerning switching operations. In order to simulate controlled loads
the loading strategy based on multi-agentsystems is integrated into the developed
simulation- and evaluation model. As an
interface to this, different control concepts
are develoved, which aim for a reduction
of component overloads, and which can be
used on the low-voltage level as well as the
medium voltage-level. Due to the modular
character of this control a directed relief of
the requested voltage-level can be achieved.
Moreover an impact on the voltage-band is
implemented using a tap-changer control
of the transformers. The effects of rising
penetration by electric vehicles with and
without load control are compared in simulations, and appropriate suggestions for the
application of the controls are given. Summarizing the results penetrations higher
than 50% can be admitted by the examined
grids using the developed controls, without
overloading any components, while uncontrolled charging is leading to significant
violations already at a penetration of 8%.
After a critical discussion of the developed
control concepts is done, possible extensions are introduced.
Claas Matrose
Schaefer, Annegret
Correlation between maintenance and incentive regulation for different asset management strategies
On 1.1.2009 came the Energy Industry Ordinance on Incentive Regulation into effect.
The network operators must adjust their an-
properties as good thermal conductivity
and high electronegativity. But as SF6
is a greenhouse gas, the actual debate on
climate change makes the search for alternatives necessary. The focus of previous investigations is set on the thermal
interruption capability of the possible SF6substitutes. In the same way the dielectric
recovery of those gases is of high importance. Preliminary investigations show an
interaction between insulating nozzles and
quenching gas which can lead to a dielectric breakdown in case of slightly axially
blown arcs. In the context of this diploma
thesis the dielectric recovery of alternative
quenching gases is further investigated.
Supervisor: Dipl.-Ing. Daniel Eichhoff,
97
nual revenue according to the revenue upper
limit determined by the Federal Network
Agency and therefore should make use of
possible efficiency improvements. Furthermore, the incentive regulation has an influence on the maintenance strategies and
on the investment behavior of the network
operators. In this work, the complete correlation between incentive regulation and
maintenance was illustrated and the consequences on the network components were
analyzed. Additionally, an asset simulation
for the revenue upper limit of the distribution network providers was developed,
which is also able to consider modified asset management strategies.
Scheefer, Christian
98
Technische Analyse gekoppelter Gleichund Wechselspannungsübertragungssysteme im europäischen Verbundnetz
The increasing volatile generation from renewable sources and the trade of electrical
energy inside liberalised electricity markets
lead to an overloaded transmission system
in Europe. An extension of the European
transmission grid is required. High Voltage
Direct Current (HVDC) technology seems
suitable for an additional overlay network.
First applications are in discussion building a connection between North African
solar power generation and the European
grid (Desertec project). The calculation
of interconnected AC/DC-systems requires
software tools, that model AC and DC
components and implement both in their
algorithms. Different software tools are
available at the Institute for High Voltage
Technology (IFHT). These tools were not
tested thoroughly regarding the calculation
of AC/DC-systems. This thesis presents
an analysis and assessment of software
tools available at the IFHT. A rating system is deduced from the theory of Usability
Engineering including the assessment of
functionality, usability, visualisation and
flexibility. Special attention is given to
the calculation of interconnected AC/DCsystems. The second part of the thesis
adapts the network model of the UCTE
transmission system to allow a first connection of solar power from North Africa
to Europe using HVDC. Two topologies
are analyzed. For each topology a linecommutated and a voltage source converted
HVDC system is implemented and compared. The connection points and transmission capacity is chosen by determining
the infeed-potential of each 380 kV node of
the European transmission grid. To calculate the interconnected AC/DC-system, the
network model has to be converted from
Matpower to a program that allows AC/DC
calculations. Converter tools are realized to
convert power flow and optimal power flow
data. For an assessment of the chosen scenarios, technical criteria are identified. The
scenarios are assessed using these criteria.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Martin
Scheufen
Tomm, Viktor
Ökoeffizienzbewertung
elektrochemischer Speichertechnologien in Energieversorgungsnetzen
The electrochemical storage technologies
are a possibility to offer ancillary services,
which are indispensable to secure net stability. In the present work the focus lies on
the application of stationary, electrochemical storage systems in the power network
as well as on the economic and ecological
evaluation of its use. Potentially favorable
operating strategies are selected and defined under economic and ecological considerations. As a part of a holistic approach
numerous environmental effects and economic feedback during the entire life cycle
are considered and included in the evaluation. Therefore the present work focuses on
Theses
Walkenfort, Matthias
Entwicklung von Managementstrategien
für Elektrofahrzeuge zur Integration in die
elektrischen Verteilungsnetze
Because of anticipated developments in the
area of electric mobility, the national grid
faces new challenges. At the same time,
new possibilities arise for network control
given that charging times of electric vehicles are variable within certain limits. Thus,
controlled charging and discharging could
have a supportive effect to the grid. However, to specifically utilize this potential,
mechanisms are needed that have a controlling impact and can therefore employ this
potential well-directed. Hence, this thesis
is about developing an algorithm that can
be used to implement complex strategies.
The genetic algorithm applied for this optimization is introduced and discussed. This
optimization method is modeled on the natural process of evolution. The process itself
is characterized by working with a set of
possible solutions. By changing and combining these solutions, they develop themselves iteratively towards an optimal solution. By including interfaces, it is possible
to develop an optimizing algorithm without
further knowledge of the simulation process. Finally, a synthetic data set is used
to verify both the optimization algorithm
itself and particular sub-functions. It has
shown that the developed algorithm is well
suitable to solve complex problems, and it
can be considered a very robust tool.
Claas Matrose
Wasowicz, Bartholomäus
Entwicklung einer integrierten handelsbasierten Einsatz- und Ausbauplanung des
deutschen Kraftwerksparks unter ökologischen Kriterien
The focus of this diploma thesis is the determination of the future composition of
power plant fleets and the energy generation structure until 2030 with the integration of the present trends in the electricity
power system, above all the political framework requirements. The main objective
is therefore the development of a model
for the longterm expansion planning of the
German power plant fleet. For a realistic
simulation of investments in power plants,
an agent-based approach is developed. This
procedure enables the modeling of expansion decisions on a yearly basis with the
net present value as the economic criterion.
The massive expansion of renewable energies as an exogenous dimension is incorporated by changing residual loads. A central
component of the model is a power plant
dispatch algorithm taking technical and
economic restrictions into account which is
employed to calculate revenues of an agent
in a liberalized power market. Simulations
are exercised for different scenarios based
on an analysis of significant influencing
variables on the development of the power
plant fleet. As result a considerable change
in the requirements for the future operation
of power plants is identified. Due to sinking and partially negative residual loads
with high volatility the demand for flexible
development of a model which simulates
the operation of a battery in a power network depending on the type and operating
strategy in accordance with technical requirements. A model of the ancillary market helps to represent the stochastic character of the achievable income. To cover also
the emissions of the production, the manufacturing process of the examined Batteries
is simulated. Evaluation of results involves
comparison of the benefit from the use of
the selected operating strategies for different types of batteries as well as determination of economic efficiency and environmental impact of influencing parameters.
Betreuer: Dipl.-Wirt.-Ing. Eva Szczechowicz, Thomas Pollok, M.Sc.
99
100
power plants is increasing. In comparison
to 2010, the total thermal installed capacity
is sinking in all scenarios until 2030, while
the demand for gas-fired power plants is rising in all investigations. In spite of a high
integration of renewable energies the fulfillment of the CO2 reduction goals of the
German government could only be nearly
realized in a scenario with an extension of
operating times of nuclear power plants.
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Martin
Scheufen
Wei, Yingze
Investigation of the influence of the network
impedance on the thermal interruption behaviour of a circuit breaker model
The interruption capability of circuit breakers is amongst others depending of the network impedance which occurs at the point
of current interruption. Hence different
switching circumstances - i.e. different grid
topologies and different types of errors cause different interruption capabilities of
a circuit breaker. The dependency of the
thermal interruption capability of a SF6 circuit breaker on the network impedance is
given in the literature. It is investigated
whether this dependency can be applied to
the circuit breaker model at the Institute for
High Voltage Technology. Therefore the
dependency of the thermal interruption capability of the existing breaker model on
the network impedance is investigated and
compared with results given in literature.
Supervisor: Dipl.-Ing.
Andreas Kurz,
Winter, Sebastian
Analyse und Modellierung der Auswirkungen technologischer Innovationen auf die
europäischen
Energieversorgungsstrukturen
This paper analyzes infrastructural devel-
opment processes of the European energy
supply system which are driven by innovation. At first the main influence factors
are determined including such of socioeconomic character. Subsequently those are
transferred to a model of the technological
and infrastructural development in Europe.
This model is based on the well established
theory of experience curves, whereat this
theory is advanced in the context of this paper to additionally describe interdependencies between innovation processes. Finally
conclusions are drawn from the results of
a scenario analysis, which predict a strong
expansion of renewable energy power generation and HVDC transmission systems
throughout Europe.
Zhang, Jingxuan
Technical and economical Analysis of possible V2G services for electrical vehicles
Electric vehicles (EVs) can store or feed energy back to the grid when they are plugged
in. For this reason, EVs have the capability to provide ancillary services to the grid
in a large population. This thesis focuses
on the investigation of technical potential
and economic profitability in providing grid
regulating services by electric vehicles. At
the beginning, technical requirements of
German regulating service market and constraints in the distribution grid have been
analyzed. Based on this analysis, a technical model was developed, in order to simulate the process of providing grid regulating
services by EVs. Then an economic model
has been developed by taking into account
additional battery degradation cost and bidding strategies on the regulating market, in
order to explore maximum profits which
can be created by EVs. In addition, service strategies and service modes in providing positive regulating service in both
Theses
Master Theses
Chitamara, Nuttawoot
Internal Arcs in Electrical Installations
- Validity Range of Pressure Calculation
Methods
Internal arcs cause a sudden pressure rise
in electrical installations. This leads to a
pressure stress acting on switchgear compartments and switchgear rooms, and could
cause building collapse. In order to predict the overpressure, pressure calculations
become essential. Nowadays, the pressure calculations can be carried out by two
methods. The first method is the CFD calculation, which employs the finite volume
method yielding to spatially resolved results. The second methodology is the improved standard calculation (ISC) method
providing spatially averaged results. Due
to this averaging and under consideration
of geometric boundary conditions, the validity range of the ISC method needs to be
investigated. For this purpose, the pressure
calculation results from both methods for
different sets of parameters are compared
in this thesis.
Supervisor: M.Sc.Kittipong Anantavanich,
Hartanti, Hesti
Development of the continuous assessment
model of transformer solid insulation condition by Fuzzy Logic approach
Condition of solid insulation has to be in
close consideration because it gives the
main effect to the ageing of power transformers. Although various relevant factors
of solid insulation can be continuously detected by online monitoring, generally only
the thermal factor is considered for the ageing model. The goal of this work is to
develop a comprehensive diagnostic model
based on all available relevant factors, e.g.
thermal, water content and gas in oil. The
Fuzzy logic approach is to be applied for
assessing the condition of solid insulation
of power transformers.
Supervisor: M.Sc. Tirinya Cheumchit
unidirectional and bidirectional way have
been presented and compared. Afterwards,
required number of EVs according to different requirements and profit range per
EV has been calculated. The technical and
economic models developed in this thesis
can be applied in the planning of V2G services. The calculated profit created by EVs
in kinds of regulating services and their required EV numbers would give a reference
to the potential V2G service organizer.
Betreuer: Dipl.-Wirt.-Ing. Eva Szczechowicz, Dipl.-Ing. Dipl.-Wirt.Ing. Thomas
Dederichs
Lund, Johan
Assessment and modeling of switching technologies for application in HVDC-circuit
breakers
In future electrical power systems based
on DC technology appropriate switchgears
are essential for switching operations during normal conditions as well as in case of
fault conditions. Contemporary AC circuit
breakers are unable to perform these operations due to their basic physical process.
Furthermore, the unavailability of HVDC
circuit breakers for high and medium voltage applications constrains the progress of
future electricity networks. To overcome
this obstacle, DC circuit breakers need to
be developed. Generally, various concepts
and technologies for DC switching exist,
e.g. semiconductor-based devices or mechanical devices as ultra-fast switches or
vacuum switches with additional resonant
circuits. Due to the high number of different technologies available, a systematic
comparison is essential for a subsequent
methodical development of a circuit breaker
101
102
for HVDC applications. Hence, the first
task of this thesis contains an intensive literature study to identify suitable technologies for DC switching. Different devices
and concepts, especially hybrid topologies
should be evaluated considering both technological and economical issues. Based
on the this analysis one breaker-setup will
be identified and studied in detail, whereas
transient stresses during switching operation are in the scope of these investigations.
For this purpose a model approach should
be developed and implemented in a simulation environment including a detailed analysis of the transient processes inside the
breaker system. Finally, the behavior of the
breaker topology should be investigated by
means of simulations of different switching operations. The Master Thesis of Mr.
Johan Lund contains mainly a theoretical
approach on the analysis of DC switching
technologies. The focus will be set on the
modeling and the simulation of the circuit
breaker topology that will be identified during the thesis.
analyzed.
Muhaimin, Emir
Pattern learning approach for monitoring
data of power transformers
Online monitoring system is supposed to
be able to give continuous supervision to
the important equipment like power transformer. Important detected and calculated
data are stored in time-series as historical
data. However, sometimes the communication part of the monitoring system does not
work properly and therefore important data
in some amounts of time are not stored.
The main goal of this work is to develop
the approach to learn the pattern of timeseries data from monitoring system in order
to fill the vacancies of these data. The different process variables have to be firstly
classified and then the pattern of data from
sample process variable of each group has
to be learned. Moreover the accuracy of
synthetic data has to be examined.
Offermann, Michael
Makhfud, Imam
Comprehensive analysis of historical data
from monitoring systems of power transformers
Comprehensive analyses of data from various process variables and transformers can
assist many important tasks for power transformer; e.g. condition assessment. However, these data from monitoring systems
are stored with different time stamps and
time slots. Therefore it is not possible to directly consider all of these data together. In
this work, the approach to manage historical data from monitoring systems for supporting comprehensive analyses has to be
developed. Moreover, data from different
transformers have to be comprehensively
Indirect investigation of the influence of
the network impendence on the interruption capability of an arc arrangement with
an alternative blowing process for circuit
breakers
Circuit breakers are key components in
modern power grids. They are designed to
switch on and off nominal currents as well
as short-circuit currents. The switching element of a circuit breaker is the switching
arc which occurs due to the interruption
process. To extinguish the switching arc it
is cooled by a quenching gas flow in axial direction. By a pressure build-up inside
the circuit breaker this gas is forced to flow
onto the switching arc at current zero. This
process is used in state-of-the-art self blast
circuit breakers. The interruption capabil-
Theses
Srisupha, Montri
Diagnostic of circuit breaker interrupter
by means of a frequency response analysis
Condition based maintenance requires detailed information about the condition of
all important components of electrical assets. For circuit breakers, the nozzle- and
contact-system is a major part for the current breaking ability. Specially the nozzle has still to be checked visually, which
requires a time consuming disassembling
of each pole. Thus, a fast, non-invasive
method was required to increase the maintenance efficiency. A frequency response
analysis (FRA) offered the possibility to
detect changes in capacitive, inductive or
ohmic arrangements. This gave us the opportunity to use it for the mentioned change
of maintenance measures.
Wild, Tobias
Investigation of arc resistance inside circuit breakers at current zero
The electric arc inside high voltage circuit breakers is surrounded by a nozzle and
cooled by a quenching gas flow. This gas
flow leads to an increase of arc resistance
close to the natural current zero crossing.
A successful interruption of the current is
strongly depending on the increasing arc
resistance. The present master thesis develops and implements a method to investigate
the dynamic behaviour of arc resistance at
current zero. Particularly not only the total
arc resistance is taken into account but the
spatial arc resistance distribution along the
axis of the arc is of interest.
ity depends on this pressure build-up and
additionally on the impedance of the network. In this thesis, an arc arrangement
with an alternative blowing process is investigated experimentally. Based on former
investigations the influence of the network
impedance on the interruption capability is
analyzed. Thus, the impedance is changed
indirectly by modifying the test object. This
change is realized by a connection of two
test objects in series. In addition to the interruption capability, by this approach the
dynamic behavior of the switching arcs can
be observed with a high speed camera. Derived from the scaling law of an axially
blown circuit breaker a scaling factor is introduced whereby a comparison of different
measurements is possible.
Bachelor Theses
Adler, Sophie
Ganzheitliche Analyse und Optimierung
des Erzeugungsmanagements von Windenergieanlagen
mittels
raum-zeitlicher
stochastischer Modelle
Bennewitz, Florian
Szenarioanalyse der Entwicklung des
deutschen Hoch- und Höchstspannungsnetzes unter ökologischen Kriterien
Betreuer: Dipl.-Ing. Thomas Helmschrott,
Bongers, Tim Dominik
Theoretical investigations for the determination of technical requirements for circuit
breakers in future DC grids
103
104
Bredtmann, Christian
Grüneberg, Philipp
Entwicklung adaptiver Multi-AgentenSysteme unter Betrachtung von Elektromobilität
Betreuer: Thomas Pollok, M.Sc., Dipl.Wirt.-Ing. Eva Szczechowicz
Ökologische Analyse des Einflusses von
Elektrofahrzeugen auf die Städteregion
Aachen
Betreuer: Dipl.-Wirt.-Ing. Eva Szczechowicz, Dipl.-Ing. Thomas Helmschrott
Erlinghagen, Philipp
Haverkamp, Philip
Entwicklung einer Methode zur topologischen Analyse und Generierung
von
synthetischen
MittelspannungsVerteilungsnetzstrukturen
Dipl.-Ing. Martin Scheufen
Szenarioanalyse zum Einfluss der Kommunikationstechnik auf zukünftige Smart Grid
Infrastrukturen
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Thomas Dederichs, Dipl.-Ing. Markus Jordans
Falke, Tobias
Heinemann, Antonia
Analyse und Modellierung von Betriebsstrategien von Energiespeichern für den
Einsatz in intelligenten Verteilungsnetzen
Analyse des Einflusses von Elektrofahrzeugen auf die V2G-Einnahmen am zukünftigen Regelenergiemarkt
Betreuer: Dipl.-Wirt.-Ing. Eva Szczechowicz, Thomas Pollok, M.Sc.
Betreuer: Dipl.-Ing. Stefan Krengel, Dipl.Ing. Dipl.-Wirt.Ing. Thomas Dederichs
Heyn, Martin
Frankeser, Sophia Johanna
Mathematical methods for the determination of the assets amount in electrical networks
Design and evaluation of different insulation and protection concepts for high voltage battery storage systems for compensation of volatile energy sources
Supervisor: Dipl.-Ing. Christoph Roggendorf
Frechen, Henning
Hinnenkamp, Mirco
Development of an algorithm for compensation of the acoustical attenuation in
XLPE
Supervisor: Dipl.-Ing. Gregor Brammer
Wirtschaftlich-technische Analyse von Lastmanagement in Versorgungssystemen mit
dezentraler Energiewandlung
Betreuer: Dipl.-Ing. Stefan Krengel, Dipl.Ing. Dipl.-Wirt.Ing. Thomas Dederichs
Gaßmann, Tim
Lauer, Anna Katharina
Analysis of the damage behavior of highest voltage disconnect switches
Bewertung von Methoden zur Lebenszyklusanalyse in Hinblick auf deren Anwendung
Theses
Möller, Robert
Analyse des Einflusses verschiedener Elektromobiltätsinfrastrukturen auf Kunden und
Netzbetreiber im Hinblick auf Aufstellungsort und Kapazitätsbedarf
Mühlbeier, Artur
Theoretical investigations on the modeling
of the dielectric recovery of hot quenching
gases in insulating nozzles
Reißing, Daniel
On the estimation of the asset amount of
electrical networks by means of synthetic
network planning
Supervisor: Dipl.-Ing. Tilman Wippenbeck
Shanmugalingam, Suganthan
Simulative investigation of a self-blast circuit breaker
Supervisor: Dipl.-Ing. Matthias Hoffacker,
Zurmühlen, Sebastian
Modellierung
des
elektromobilen
Verkehrs unter Berücksichtigung sozioökonomischer
Daten
und
Analyse
der
Auswirkungen
auf
elektrische
Verteilungsnetze
Study Theses
Brust, Martin
Preliminary investigations of electrical and
mechanical properties of syntactic foam
based on flexible formulated epoxy resins
Buß, Stefan
Investigation of the influence of the nozzle geometry of a self-blast circuit breaker
model
Dipl.-Ing. Ming Tang
Frehn, Tobias
Investigation of the influence of the test circuit on the interruption limit of a circuit
breaker model
Dipl.-Ing. Matthias Behle
Schneider, Jurij
Siegler, David
Analyse des Einflusses ortsbezogener Subventionen auf die Entwicklung erneuerbarer Energieträger
Betreuer:
Dipl.-Ing.
Dipl.-Wirt.Ing.
Thomas Dederichs, Dipl.-Wirt.-Ing. Baris
Özalay
in Systemen der dezentralen Energiewandlung
Betreuer: Dipl.-Ing. Stefan Krengel, Dipl.Wirt.-Ing. Eva Szczechowicz
Investigation on the impact of alkali-ions
on the water absorption of syntactic foam
Supervisor: Dipl.-Ing. Anja Strauchs,
Vobis, Daniel
105
Preliminary investigations of electrical and
mechanical properties of syntactic foam
based on flexible formulated epoxy resins
model
Projects
Iloba, Nnamdi
Weiß, Beatrix
Temperature measurement inside the heating volume of a self-blast circuit breaker
106
Influencing factors on the condition of
power transformer components
Seminar Switchgear and Substations
Voltage
The seminar „High and Medium Voltage Switchgears and Substations“ imparts basic
knowledge about design and function of components and substations for electrical energy
transmission and distribution. The main focus lays on physical basics and economical aspects of switchgears and substations. This seminar is suitable for engineers and technical
staff coming from industry, utilities and universities as well as for students of RWTH Aachen
University.
After the great success of the last years,
the seminar „High and Medium Voltage
Switchgears and Substations“ was also
arranged in 2010 on 21th and 22th of
June. The seminar is carried out annually
in co-operation between the Institute for
High Voltage Technology, the VDE Regio
Aachen, the Forschungsgemeinschaft für
elektrische Anlagen und Stromwirtschaft
e.V. Mannheim and the RWTH International Academy GmbH. This year, the event
was visited by 60 representatives from industry and utilities as well as 120 scientific employees and students of IFHT. For
this two-day advanced training course the
in-house auditorium Eph was booked.
benefit from the proficiency and know-how
in the following discussions. The pause
times provided great opportunities for further questions and interesting discussions
and enabled students to establish further
contacts to the industry.
107
Abb. 2: Speakers: Dr.-Ing. Martin Schumacher
(left), Dipl.-Ing. Frank Hofmann (right)
Abb. 1: Venue auditorium Eph
Reputable speakers presented various topics concerning switchgears and substations
and their physical fundamentals as well as
their economical aspects. This way, the participants gained a comprehensive and practical insight on these topics and were able to
Seminar High and Medium
Switchgears and Substations
In the following an overview over this
year’s seminar programm is given:
• Welcome
Prof. Dr.-Ing. Armin Schnettler,
RWTH Aachen,
Institut für
Hochspannungstechnik
• Introduction
Dr.-Ing. Martin Schumacher,
ABB Schweiz AG Hochspannungsprodukte, Zürich
• Electric Arcs in Circuit Breakers
Dr.-Ing. Martin Kriegel,
ABB Schweiz AG, Zürich
• SF6-High Voltage Circuit Breakers
Dipl.-Ing. Nils Werning,
Siemens AG Energy
Schaltwerk Berlin
Sector,
ABB AG Calor Emag Mittelspannungsprodukte, Ratingen
• Vacuum Circuit Breakers
Dr.-Ing. Dietmar Gentsch,
ABB AG Calor Emag Mittelspannungsprodukte, Ratingen
• Cables and Overhead Lines
Dr.-Ing. Frank Merschel,
RWE Rheinland Westfalen Netz AG,
Essen
• High Voltage Fuses
Dipl.-Ing. Johannes-Georg Gödeke,
SIBA GmbH & Co. KG, Lünen
• Disturbances of Electricity Supply
Equipment
Prof. Dr.-Ing. Armin Schnettler,
RWTH Aachen,
Institut für
Hochspannungstechnik
• High Voltage Direct
Transmission
Dr.-Ing. Jutta Hanson,
ABB AG, Mannheim
Current
• Introduction into System Engineering
and
Gasisolated
Switchgears
Dr.-Ing. Martin Schumacher,
ABB Schweiz AG Hochspannungsprodukte, Zürich
• Airinsulated Switchgears
Dipl.-Ing. Gerd Lingner,
Siemens AG, Energy Sector, Power
Transmission Division, Erlangen
108
• Local Network Substations
Dipl.-Ing. Gisbert Brüggemann,
Viva Electrica!, Wetter
• Power Transformers
Dipl.-Ing. Frank Hofmann,
AREVA Energietechnik GmbH,
Mönchengladbach
• Medium Voltage Switchgears
Dr.-Ing. Stefan Göttlich,
Finally, an excursion to the transformer
factory of AREVA Schorch Energietechnik GmbH in Mönchengladbach and to the
400 kV substation of STAWAG Aachen
at Aachener Kreuz was provided for
all students. We would like to thank
again STAWAG Aachen and AREVA
Mönchengladbach for the outstanding support during our visit. We also want to thank
all speakers for their interesting presentations during the two-day seminar. Due to
the positive resonances of the participants,
it is planned to offer the seminar „High and
Medium Voltage Switchgears and Substations“ again in 2011.
Contact
Dipl.-Ing. Anja Strauchs
[email protected]
+49 241 80-94920
Seminar Protection and control systems
The seminar “Protection and control systems” offered for the first time at RWTH Aachen
took place from 14th -18th November 2010 in Vorarlberg, Austria on invitation of
OMICRON electronics GmbH. The aim of the seminar is to give students, especially the
power engineering ones, a practical insight into the special world of protection and control
in electrical power systems.
Reflection by RWTH Aachen
Based on the kind invitation of OMICRON
electronics GmbH, the RWTH Aachen for
the first time offered a seminar on “Protection and control systems” to ten interested
students in the winter term 2010-2011,. The
application process allowed for selecting
ten highly motivated students covering a
wide range of fields of interest in power
engineering and protection and control systems experience.
This group of interested students met Mr.
Rainer Luxenburger from OMICRON electronics GmbH, who is a skilled and very
experienced speaker on the subject. In the
three days of the seminar Mr. Luxenburger
gave insight to the theoretical and practical world of protection by presentations,
lively discussions and practical demonstrations.Mr. Luxenburger illustrated selected
topics of classical power system protection
and future challenges caused by the integration of distributed generators and storage devices. In the aftermath of the seminar, reports on further topics will deepen
the insight into the field of protection. The
visit of the switching station Bürs of Vorarlberger Kraftwerke AG illustrated the seminar content again in the systemic context.
The excellent accommodation and food for
the seminar group at the seminar house in
Laterns offered an excellent physical, atmospheric and social basis for a successful
seminar and for the necessary regeneration.
Diversified social events in the evenings allowed for refreshment and provided an opportunity for closer acquaintance after in-
tensive seminar days. The students had
the opportunity to get to know OMICRON
electronics by talking to employees and in
a guided tour demonstrating the excellent
working conditions as well as the activities
of OMICRON electronics.
We would like to thank OMICRON electronics GmbH again for the invitation and
the successful seminar. Personally, we
would like to thank Mr Luxenburger as
speaker and Ms. Erika Fimpel for the excellent organization and support on site. We
look forward to further cooperation and the
next seminar.
Our thanks at this point also aims at Vorarlberger Kraftwerke AG for kindly enabling
the guided tour in the substation Bürs by
two highly experienced specialists.
Reflection by OMICRON electronics
GmbH
”We were very pleased that the RWTH
Aachen followed our invitation to the seminar “Protection and control systems” to Vorarlberg. Since the cooperation with IFHT
means a lot to us, it was our special concern to give a very motivated and interested
group of students a closer insight to protection technology in form of practical lecture
by our expert Rainer Luxenburger.
Besides the intensive course, the students
also had the opportunity to examine the
protection at substation in Bürs and thereby
to see the theory put into practice. We have
also tried to give the students an insight into
the company OMICRON and hope to have
Seminar “Protection and control systems”
109
Abb. 1: Group picture
110
somewhat loosened up the seminar by the
evening program.
We look forward to welcome and host another equally motivated group of students
next time and look forward to continuing
our good cooperation with the IFHT.”
Kontakt
[email protected]
+49 241 80-90015
The Institute
111
Chronicle 2010
04.01.10
First working day of Mathias Knaak, Jens
Knauel, Daniel Winkel
11.01.10
First working day of Johannes Stüeken
15.01.10
First working day of Thomas Helmschrott,
Baris Özalay
15.01.10
Visit of the company CONSENTEC with
guided tour of the institute
Armin Schnettler and Christian Hille
15.01.10
Attendance at FGLA-Colloquium „Electromobility“
Stefan Federlein, Thomas Smolka, Bernhard Schowe-von der Brelie
112
17.01.10
Last working day of Martin Splettstößer
29.01.10
Last working day of Walter Taeter
28.01. - 03.02.10
DAAD-Preselection meeting for scholarship applicants (research scholarships)
from the Russian Federation and selection
interviews with applicants for scholarships
(master programme) in Moscow
Attendant: Gerhard Pietsch
01.02.10
First working day of Stefan Krengel,
Tilman Schmidt
03.02.10
Visit of Prof. Dr. Mihai Cernat, University
of Brasov, Romania at IFHT
05.02.10
Conference of the project-related committee to the AiF-Intention „Reduction of the
compression load in electrical equipment in
case of fault arc“ in Aachen
Attendants: Gerhard Pietsch, Kittipong
Anantavanich, Daniel Eichhoff
14.02.10
High voltage prom at IFHT
18.02.10
Preselection meeting of the Mummertfoundation (future leadership) for scholarship holders from Eastern European countries in Cologne
20.02. - 02.03.10
Armin Schnettler lectures at TGGS in
Bangkok
24.02. - 02.03.10
Christian Hille visits the TGGS in Bangkok
01.03. - 31.03.10
The Ph.D. students Viktor Belka and Yuri
Soloview from Saint-Petersburg State Polytechnical University, Russia, attend the institute for a study visit within the LeonhardEuler-Project „Investigations of high voltage technology components“
05.03.10
Doctoral examination of Kittipong Anantavanich with subject „Calculation of pressure rise due to internal arcs considering
SF6-air mixtures and arc energy absorbers“
Reviewer: Gerhard Pietsch, Second reviewer: Hans-Jürgen Haubrich
05.03.10
Doctoral examination of Ming Chark Tang
with subject „Widerstandsverteilung von
Schaltlichtbögen in Selbstblasleistungsschaltern während der Stromnulldurchgangsphase“
Reviewer: Armin Schnettler, Second reviewer: Michael Kurrat
13.03. - 18.03.10
Selection
Azerbaijan
governmentscholarship holders (with participation of
Chronicle
19.03. - 27.03.10
CIGRE-Working Group Meeting A3.24
(fault-arc simulation) and CIGRE Technical Seminar „Modelling and Testing of
Transmission and Distribution Switchgear“
in Brisbane/Australia
Lecture of Gerhard Pietsch
25.03.10
Workshop „Aachen als Modellregion für
Elektromobilität“, Tivoli Aachen
Lecture of Armin Schnettler
29.03.10
Student internship in mathematicalphysical science area
Martin Statz, Einhard-Gymnasium Aachen
27.04.10
DKE conference „Die Zukunft elektrisiert!“ in Offenbach
Lecture of Armin Schnettler
29.04.10
Doctoral examination of Stefan Federlein with subject „Modellierung des typspezifischen Störungsaufkommens von
Hochspannungs-Schaltgeräten“
Reviewer: Armin Schnettler, Second reviewer: Gerd Balzer
30.04.10
Last working day of Kittipong Anantavanich
30.04.10
Last working day of Ming Tang
03.05.10
First working day of Sebastian Winter
06.05. - 08.05.10
DAAD-Preselection meeting scholarship
for alumni of german schools in foreign
countries (new applications) in Bonn-Bad
Godesberg
10.05.10
First working day of Jenny Jaensson-
Weidner
15.05.10
Mannheim Marathon, Organiser: Christoph
Roggendorf
Attendants: Jan Becker, Florian Bennewitz,
Tim Bongers, Christian Bredtmann, Ilka
Bremer, Denys Demenko, Daniel Eichhoff, Andreas Höwedes, Claas Matrose,
Robert Möller, Armin Schnettler, Johannes
Stüeken, Beatrix Weiß, Daniel Winkel
24.5. - 28.05.10
Whitsun study trip
25.05.10
First working day of Frederik Kalverkamp
DAAD) in Baku/Azerbaijan
31.05.10
Last working day of Thomas Smolka and
Mathias Behle
01.06. - 04.06.10
BMBF - journey Shanghai, China
Attendant: Armin Schnettler
03.06.10
Honor of Bartholomäus Wasowicz and
Fabian Potratz for the project idea „Plug
Into Future“ at the competition for students
of the governmental department for education and research „Energie für Ideen“
Supervising tutor: Thomas Dederichs
15.06.10
Prof. Szkutnik, Prof. Kocak at IFHT
21.06. - 22.06.10
Seminar „Hoch- und Mittelspannungsschaltgeräte und -anlagen“
Supervisor: Martin Schumacher
29.06.10
2. congress to smart grids, the internet of
energy and the intelligent electromobility,
at Eurogress Aachen
Lecture of Thomas Dederichs
01.07.10
First working day of Jochen Roder and
Michael Kippen
02.07.10
Doctoral examination of Michael Keßler
113
with subject „Einsatz von elastischen syntaktischen Schäumen in der Hochspannungstechnik“
Reviewer: Armin Schnettler, Second reviewer: Volker Hinrichsen
02.07. - 04.07.10
Sailing weekend of IFHT at Veerse Meer
09.07. - 10.07.10
DAAD-Preselection meeting scholarship
for alumni of german schools in foreign
countries (extensions) in Bonn-Bad Godesberg
12.07.10
Doctoral examination of Jörg Feldmann
with subject „Planungsgrundsätze für
Niederspannungsnetze unter Berücksichtigung von Versorgungsqualität und Kosten“
Reviewer: Hans-Jürgen Haubrich, Second
reviewer: Armin Schnettler
114
02.08.10
First working day of Sepideh Doroudian
and Bernhard Fuchs
18.08.10
IFHT staff day to the Ahrtal, governmentbunker Bad Neuenahr, wine tasting and
guided tour at the winegrowers cooperative Mayschoss
21.08.10
Rad am Ring, Nürburgring
Attendants:
Christian Hille, Matthias
Hoffacker, Tobias Küter, Lutz Malchus,
Claas Matrose, Mark Meuser, Andreas
Nolde, Thomas Pollok, Ralf Puffer,
Christoph Roggendorf, Daniel Schacht,
Oliver Scheufeld, Armin Schnettler
22.08. - 27.08.10
CIGRÉ Session 2010 in Paris
Attendants: Thomas Dederichs, Stefan
Federlein, Ralf Puffer, Armin Schnettler
22.08. - 24.08.10
CIGRE-Working Group Meeting A3.24
(fault-arc simulation) in Paris
01.09.10
First educational day of Volker Lontzen
03.09. - 18.09.10
Excursion to Australia
Attendants: Gregor Brammer, Thomas
Dederichs, Stefan Federlein, Christian
Hille, Matthias Hoffacker, Maximilian
Keller, Michael Keßler, Andreas Kurz,
Andrey Mashkin, Claas Matrose, Gerhard Pietsch, Thomas Pollok, Ralf Puffer,
Christoph Roggendorf, Martin Scheufen,
Armin Schnettler, Anja Strauchs, Eva
Szczechowicz
06.09. - 11.09.10
„International Conference on Condition
Monitoring and Diagnosis“ (CMD 2010)
in Tokyo (Japan)
Attendant: Tirinya Cheumchit
15.09.10
First working day of Rita Kurth
28.09. - 30.09.10
DAAD-Scholarship seminar for alumni of
german schools in foreign countries and
language schools in Berlin
Lecture of Gerhard Pietsch
30.09.10
Last working day of Jenny JaenssonWeidner
30.09.10
Handover of the E-Fiat 500 to institutes of
the RWTH Aachen (two cars to the IFHT)
with attendance of Aachen’s mayor
01.10.10 Andrey Mashkin gets the EEIM
John Neal Award for the paper „Analysis
on the Electrical Properties of Syntactic
Foam Under Various DC Field Stresses“
01.10.10
Conference of the project-related committee to the AiF-Intention „Reduzierung der
Druckbeanspruchung elektrischer Anlagen
im Störlichtbogenfall“ in Aachen
Attendants: Gerhard Pietsch, Daniel Eich-
Chronicle
04.10.10
First working day of Lars Schröder, electronic laboratory
18.10.10
Armin Schnettler signs a cooperation agreement „Clarification of properties of controlling pressure rise due to fault arcs“ with the
Central Research Institute of Electric Power
Industry (CRIEPI), Japan
25.10. - 28.10.10
DAAD-Preselection meeting for the awarding of scholarships for candidates from the
Russian Federation due to the LomonossovProgramme in Moscow
01.11.10
Discussion of the research group CIGRE
A3 in Aachen
Attendants: Armin Schnettler, Gerhard
Pietsch
02.11.10
First working day of Gregor Nicolic
04.11.10
Doctoral examination of Michael Roscher
Reviewer: Dirk Uwe Sauer, Second reviewer: Armin Schnettler
08.11.10
First working day of Hendrik Natemeyer
08.11. - 09.11.10
VDE Kongress in Leipzig 2010
Attendants: Armin Schnettler, Stefan Federlein, Sepideh Doroudian, Thomas Helmschrott, Christian Hille, Stefan Krengel,
Thomas Pollok, Eva Szczechowicz
09.11.10
Bestowal of the SAG Award (2nd place) to
Stanislav Votruba within the eStudend days
at the VDE congress in Leipzig
10.11.10
Bestowal of the price of the Otto-JunkerStiftung to Philipp Masmeier for the
diploma thesis with subject „Theoretische und experimentelle Untersuchung von
Lichtbogenform und Schaltverhalten in
Leistungsschalter-Modellanordnungen mit
alternativen Düsengeometrien“ / „Theoretical and experimental investigation of the
switching behaviour and the form of the
electric arc in circuit breaker model arrangements with alternative nozzle geometries“
12.11.10
Anja Strauchs gets the IEEE DEIS Graduate Award 2010 for outstanding PhD works
on the field of electrical insulation systems,
dielectrics and high voltage technology
hoff
13.11.10
„34. Hochwissenschaftliches Kolloquium“
at IFHT with award of the price „Mann mit
der ruhigen Kugel“ to Thomas Dederichs
22.11.10
First working day of Markus Gödde
14.12. - 17.12.10
DAAD-Preselection interviews with scholarship applicants (master programme) in
Skopje/Macedonia
17.12.10
Doctoral examination of Torsten Wirz with
subject „Verfahren zur Optimierung der Ultraschalldiagnostik an polymeren Isoliersystemen“
Reviewer: Armin Schnettler, Second reviewer: Ernst Gockenbach
30.11.10
Last working day of Leo Künzer, electronic
laboratory
31.12.10
Last working day of Michael Kippen
115
116
Publications
Kittipong
Anantavanich,
Gerhard
Pietsch, Daniel Eichhoff
Importance of SF6-air gas data for pressure calculation due to fault arcs in electrical
installations
Proc. XVIIIth Int. Conf. on Gas Discharges
and Their Appl., Greifswald, 2010 Germany, pp. 122-125
Kittipong Anantavanich
Calculation of Pressure Rise in Electrical
Installations due to Internal Arcs Considering SF6-Air Mixtures and Arc Energy Absorbers
RWTH Aachen University, Dissertation
2010, Aachener Beiträge zur Hochspannungstechnik - Band 14, Verlagshaus
Mainz, ISBN 3-86130-677-8
Tobias Blank, Stephan Thomas, Christoph Roggendorf, Thomas Pollok, Ionut
Trintis, Dirk Uwe Sauer
Design and construction of a test bench
to characterize efficiency and reliability of
high voltage battery energy storage systems
32nd International Telecommunications
Energy Conference (INTELEC), Orlando,
FL, USA, 6-10 June 2010
Tirinya Cheumchit, Armin Schnettler,
Thanapong Suwanasri
Derivation of Aging Characteristics for
Power Transformers by Artificial Intelligence Techniques
Conference Proceedings of CMD 2010
Stefan Federlein, Bartosz Rusek
Praxisnahe Modellbildung zur Bewertung des Störungsaufkommens von
Hochspannungs-Schaltgeräten
FGH-Fachtagung, Heidelberg, September
2010
Stefan Federlein, Claas Matrose
SmartWheels - Intelligente Elektromobilität
in der Modellregion Aachen
RWTH Themen, Elektromobilität made in
Aachen, Ausgabe 02/2010, ISSN-Nr. 0179079X
Stefan Federlein
Modellierung des typspezifischen Störungsaufkommens von HochspannungsSchaltgeräten
RWTH Aachen University, Dissertation 2010, Aachener Beiträge zur Hochspannungstechnik - Band 15, Verlagshaus
Mainz, ISBN 3-86130-678-6
Thomas Helmschrott, Devid Perissinotto,
Martin Scheufen, Armin Schnettler
Integriertes Verkehrs- und Energieflussmodell / Integrated Modeling of Traffic and
Power Flows
VDE-Kongress 2010, Leipzig, November
2010
Thomas Helmschrott, Devid Perissinotto, Martin Scheufen, Armin Schnettler
Integriertes Verkehrs- und Energieflussmodell
Internationaler ETG-Kongress, Leipzig,
November 2010
Mikimasa Iwata, S. Tanaka, T. Ohtaka,
T. Miyagi, T. Amakawa, Kittipong Anantavanich, Gerhard Pietsch
CFD Calculation of Pressure Rise and Propagation Depending on Arc Energy in a
Closed Container
Proc. XVIIIth Int. Conf. on Gas Discharges
and Their Appl. 2010, Greifswald, Germany, pp. 146-149
Mikimasa Iwata, Kittipong Anantavanich, Gerhard Pietsch
Publications
Mikimasa Iwata, S. Tanaka, T. Othaka,
T. Amakawa, Kittipong Anantavanich,
Gerhard Pietsch
Influence of electric arc energy on pressure rise and propagation due to high current
fault arc in a closed container
Records of the 2010 Annual Meeting I.E.E.
Japan, paper 6-206, 2010, p. 350
Christoph Kahlen, Holger Krings, Peter Wittlinger, Bernhard Schowe-von der
Brelie, Stefan Federlein, Claas Matrose,
R. Frings, Thomas Smolka
Einflüsse und Auswirkungen von Elektromobilität auf das Energieversorgungsnetz
sowie Anforderungen und Voraussetzungen
für eine interoperable Netzintegration
Internationaler ETG-Kongress, Leipzig,
November 2010
Michael Kessler, Armin Schnettler
Investigation of the DC Breakdown Mechanism in Elastic Syntactic Foams
IEEE Transactions on Dielectrics and Electrical Insulation, Vol. 17, Issue 3, pp. 898905, IEEE, Juni 2010
Michael Kessler, Christoph Roggendorf,
Armin Schnettler
Behavior of Elastic Syntactic Foams under
Impulse Voltage Stress
Conference Record of the 2010 IEEE, International Symposium on Electrical Insulation (ISEI), 4 Seiten, San Diego (USA) 6.-9.
Juni 2010
Michael Keßler
Einsatz von elastischen syntaktischen
Schäumen in der Hochspannungstechnik
RWTH Aachen University, Dissertati-
on 2010, Aachener Beiträge zur Hochspannungstechnik - Band 16, Verlagshaus
Mainz, ISBN 3-86130-679-4
Stefan Krengel, Thomas Dederichs, Thomas Smolka, Armin Schnettler
Scenario Analysis about Ecological and
Economical Benefits of Dispersed Generation in Future Energy Networks
Third International Conference on EcoEfficiency, Egmond aan Zee, Juni 2010
Stefan Krengel, Armin Schnettler, Thomas Dederichs, M. Bertling, J. Biermann, T. Gervens, M. Fiedeldey, E.-P.
Meyer
Das Virtual Power System Allgäu - der Pilotbetrieb
2010
Andreas Kurz, Martin Seeger, Daniel
Eichhoff, Armin Schnettler
Determination of the dielectric recovery inside insulating nozzles concerning gas flow
Proc. XVIII International Conference on
Gas Discharges and Their Applications,
Greifswald 2010, pp. 58-61
Andreas Kurz, Christof Kahlen, Ming
Chark Tang, Matthias Hoffacker, Armin
Schnettler
Investigation of New Nozzle Geometries
and their Influence on the Interruption Behaviour for Gas Circuit Breaker
Proc. XVIII GD 2010, International Conference on Gas Discharges and Their Applications, Greifswald, Germany 2010, pp.
166-169
Andrey Mashkin
Analysis on the Electrical Properties of
Syntactic Foam Under Various DC Field
Stresses
European Electrical Insulation Manufacturers John Neil Award 2010
Influence of Current and Electrode Material on Fraction kp of Electric Arc Energy
Leading to Pressure Rise in a Closed Container During Internal Arcing
IEEE Trans. Power Del., Vol. 25, No. 3,
2010, p. 2028 - 2029
117
118
Andrey Mashkin, Anja Strauchs, Armin
Schnettler, Bernd Freiheit-Jensen, Arne
Lunding
Einfluss der inneren Feldstärkeverteilung
auf die elektrische Durchschlagfestigkeit
von syntaktischem Schaum / The Impact
of the Internal Field Distribution on the
Breakdown Strength of Syntactic Foam
ETG-Fachtagung:
Isoliersysteme
bei
Gleich- und Mischfeldbeanspruchung; 27.28.9.2010; Köln
Andrey Mashkin, Anja Strauchs, Armin
Schnettler, Arne Lunding
The Impact of Different Alkali Ion Concentrated Hollow Glass Microspheres on the
Electrical Breakdown Mechanism of Syntactic Foam
10th IEEE International Conference on Solid Dielectrics (ICSD); July 4th -9th, 2010;
Potsdam, Germany
Andrey Mashkin, Anja Strauchs, Armin Schnettler, Jörn Podlazly, KarlMika Reß
Investigation on Inverse Volume Effect of
Syntactic Foam under Uniform dc Field
Stress
IEEE International Symposium on Electrical Insulation (ISEI) 2010; 6.-9.Juni 2010;
San Diego, USA
Claus Neumann, Bartosz Rusek, Christian Schorn, Stefan Federlein, Armin
Schnettler, Gerd Balzer, Thomas Krontiris
Modelling the effect of maintenance on failure occurrence and lifetime management
of high voltage circuit breakers
CIGRE Session, A3-203, Paris (France)
2010
Thomas Pollok, Eva Szczechowicz, Claas
Matrose, Georg Stöckl, Georg Kerber,
Martin Lödl, Armin Schnettler, Rolf
Witzmann, Petra Behrens
Flottenversuch Elektromobilität - Netzma-
nagementstrategien mittels elektrifizierter
Fahrzeugflotten
2010
Ralf Puffer
Netzoptimierung durch witterungsabhängigen Freileitungsbetrieb und Hochtemperaturleiter
Deutsche Umwelthilfe (DUH) Netzkongress 2010, Erneuerbare ins Netz, Berlin
2010
Ralf Puffer
Möglichkeiten zur Erhöhung der Strombelastbarkeit von Freileitungen am Beispiel
von Freileitungs-Monitoring und Hochtemperaturleitern
6. ETP-Konferenz Instandhaltung von Freileitungen und Freileitungsmasten, 2010,
Frankfurt
E. Rijks, G. Sanchis, G. Balzer, Stefan
Federlein, G. Ford, A. Gaul, T. Jesson, K.
Sand, B. Sander, S. Voronca et al.
Transmission Asset Risk Management
Cigré Working Group C1.16, TB 422, Paris
2010
E. Rijks, G. Sanchis, G. Balzer, Stefan
Federlein, G. Ford, A. Gaul, T. Jesson, K.
Sand, B. Sander, S. Voronca, et al.
Transmission Asset Risk Management
Cigré Working Group C1.16, TB 424, Paris
2010
Christoph Roggendorf, Michael Kessler,
Sascha Schulte, Armin Schnettler
Accelerated Test Procedures for Hydrothermal Aging
Conference Record of the 2010 IEEE International Symposium on Electrical Insulation (ISEI), 5 Seiten; San Diego (USA) 6.-9.
Juni 2010
Martin Scheufen, Ralf Puffer, Bartosz
Rusek
Publications
Michael Schmale, Hans-Joachim Dräger,
Ralf Puffer
Implementation and Operation of a Cable
Monitoring System in Order to Increase the
Ampacity of a 220-kV Underground Power
Cable
CIGRE Session, B1-113, Paris (France)
2010
Michael Schmale, Ralf Puffer, HansJoachim Dräger
Optimierung der Strombelastbarkeit eines
220-kV Kabels / Ampacity Improvement of
a 220-kV Underground Cable
E.ON, Bayreuth 2010
Michael Schmale, Hans-Joachim Dräger,
Ralf Puffer, Reinhold Kliegel
Freileitungs-Monitoring - Entwicklung und
Einführung eines Systems zur witterungsabhängigen Erhöhung der Strombelastbarkeit von Freileitungen / Development and
Implementation of a Monitoring System for
Weather Based Dynamic Rating of Overhead Lines
E.ON, Bayreuth 2010-09-08
Michael Schmale, Ralf Puffer
Freileitungs-Monitoring im 380-kV-Netz Freileitungen sicher betreiben und Reserven nutzen
Netzpraxis, Jg.49 (2010), Heft 11
Anja Strauchs, Andrey Mashkin, Armin Schnettler, Alexander Tröger, Bernd
Wandler
Einfluss von Temperatur und elektrischer
Feldstärke auf die elektrische Leitfähigkeit
und Spannungsfestigkeit von syntaktischem
Schaum
ETG Fachtagung, Isoliersysteme bei
Gleich- und Mischfeldbeanspruchung; 27.28.9.2010; Köln
Anja Strauchs, Andrey Mashkin, Armin
Schnettler, Jörn Podlazly
The Impact of Water Absorption on the
Dielectric Properties of Syntactic Foam
10th IEEE International Conference on Solid Dielectrics (ICSD); July 4th -9th, 2010;
Potsdam, Germany
Anja Strauchs, Andrey Mashkin, Armin
Schnettler, Jörn Podlazly, Bernd Wandler
The Impact of Electrical Field Stress on the
Volume Conductivity of Syntactic Foam
IEEE International Symposium on Electrical Insulation (ISEI) 2010; 6.-9.Juni 2010;
San Diego, USA
Anja Strauchs, Andrey Mashkin, Armin Schnettler, Jörn Podlazly, Bernd
Freiheit-Jensen
Investigations on the Partial Discharge Behavior of Syntactic Foam under Uniform
Field Stress
IEEE International Symposium on Electrical Insulation (ISEI) 2010; San Diego, USA
6.-9.Juni 2010
Ming-Chark Tang
Widerstandsverteilung in Schaltlichtbögen
von Selbstblasleistungsschaltern während
der Stromnulldurchgangsphase
RWTH Aachen University, Dissertation
2010, Aachener Beiträge zur Hochspannungstechnik - Band 13, Verlagshaus
Mainz, ISBN 3-86130-676-X
M. Wietschel (Herausgeber), M. Arens,
C. Dötsch, S. Herkel, W. Krewitt, P. Merkewitz, D. Möst, Martin Scheufen
Energietechnologien 2050 - Schwerpunkte
für Forschung und Entwicklung
Frauenhofer Verlag 2010 (ISSN: 16127455); ISBN: 978-3-8396-0102-0
Analyse der Strombelastbarkeit von Freileitungen mit Freileitungs-Monitoring bei
kleinen Windgeschwindigkeiten
GIS-Anwenderforum 2010, Darmstadt
119
POSTER SESSIONS
Tirinya Cheumchit, Armin Schnettler,
Thanapong Suwanasri
Derivation of Aging Characteristics for
Power Transformers by Artificial Intelli-
120
gence Techniques
CMD-Konferenz, Tokyo (Japan) 2010
Technical Excursion
An excursion with professors and assistants is conducted at regular intervals of three to
four years at the institute for high voltage technology (IFHT). This year’s excursion went to
Down Under. After a flying time of approx. 24 h, four stations on the east coast were visited
within 12 days. The trip started in Frankfurt, through Singapore as a stopover, to the metropolises like Melbourne, Sydney and Brisbane, but also to the tropical Cairns. During the
time, numerous companies, universities and places of interest were visited, where existing
contacts have been refreshed and new established.
Melbourne 05.-08.09.2010
The first visiting point was Melbourne located in southeast of Australia, which revealed his diversity of the Australian lifestyle during a sightseeing tour on the first
day. Then, the first business related trip started on the next day (Monday) in the morning to Traralgon. There, we got to see the
power station Loy Yang as well as the adjacent brown coal open-cast mining. In this
context, it was interesting to figure out, that
Australia has more than enough installed
power plant capacities and raw materials like coal and brown coal available however,
the water shortage of the country has a significant impact on management and operation of power stations. In addition, the actual growth of population is an essential challenge in the operation and construction of
assets.
From the power station it then only was few
miles to the Basslink converter station. The
Basslink interconnector links South Australia with Tasmania over a HVDC line. Here, even for a distance of 295 km, submarine cables at a voltage of approx. 400 kV
are used to transmit 500 MW of electrical
power.
Olex the largest cable manufacturer of Au-
Institute excursion to Australia
03.-18.09.2010
stralia gave a comprehensive insight into
the cable production on the third day in
Melbourne before heading for the first domestic flight to Sydney.
121
fig. 1: Participants of the Australia excursion in
the open-cast mining in Traralgon
Sydney 08.-10.09.2010
After arrival in Sydney, the largest aquarium in the southern hemisphere was visited as part of a city tour. The highlight of
the city tour was certainly the Sydney Opera House, which was declared as UNESCO world heritage in 2007. On Thursday
morning AEMO (Australian Energy Market Operator) gave an insight into the structure of the Australian energy market and the
significant ongoing challenges in the planning and operation of assets - primarily driven by the rapid growth of population. In
the afternoon the 330 kV GIS Haymarket
substation in the heart of Sydney, operated by Transgrid (an Australian transmission system operator), has been visited. The
substation belongs to one of the largest in
the world with a transmission capacity of
1200 MVA. It therefore was a very impressive substation, but with an inconspicuous
exterior design. On 10/09/2010, we arrived
at AGL (Australian Gas Light Company),
the largest Australian electricity and gas
supplier at the same time dealing with the
highest share of renewable energies in Australia. Among other things, the attractiveness of participating in the Australian energy market through a differentiated range
of products was shown. Finally, we moved
from subtropical Sydney to tropical Cairns
in northern Australia through the weekend.
A 7.5 km long funicular railway
through the primeval forest provided a great view over the treetops and the Barron Gorge waterfalls.
fig. 3: Whitewater Rafting at Barron River
Brisbane 13.-17.09.2010
122
fig. 2: Opera House and Harbour Bridge in Sydney
Cairns 10.-13.09.2010
The very special activities in a tropical surrounding during the weekend offered impressive scenery of the Australian rain forest which was complemented with the
Whitewater Rafting on Barron River.
The highlight of the weekend was a day
trip to the Great Barrier Reef from Port
Douglas. At three different places fantastic
coral formations, colourful fish and even
reef sharks have been seen. Finally, a half
day tour ended up in the Australian “jungle”.
At the beginning of the second week the
last domestic flight went to the east of Australia, Brisbane. Here both campus universities Queensland University of Technology and University of Queensland were visited on Tuesday. During a mixed workshop
an exciting scientific exchange between the
Australian university and our institute was
initiated, which also established new contacts to these universities.
The last trip - taking an entire day - was
spent together with the company Powerlink , which kindly guided us to a transformer substation equipped with hybrid GIS
system. Afterwards, the Wivenhoe power
station was visited. The latter spot is a
pump storage with two 250 MW turbines,
operated by Tarong Energy. The Wivenhoe Dam creates the artificial Lake Wivenhoe, which at the same time also serves as drinking water storage for the metropolitan area of Brisbane. The day trip
finished in the Lone Pine Koala Sanctuary, in which, among other things, nume-
Technical Excursion
fig. 5: Shipping tour on Brisbane River
fig. 4: Koala in the Lone Pine Koala Sanctuary
Park
The headquarters of AEMO, which is located in Brisbane, was the last company to
be visited during the Australia trip. Here,
the topic was a detailed presentation of the
structure and the challenges of the Australian energy market. The big difference of the
Australian compared to European grids is
reasoning in its huge longitude with an only low meshed structure. Afterwards, typical Australian animals such as various spiders and snakes have been admired in the
Queensland museum.
With many new impressions we finally left
the interesting and amazing country of Australia with some new experiences on board
on Friday.
rous koalas and kangaroos could be fed.
Coordinators of this excursion and authors
of this article:
Dr.-Ing. Michael Keßler
[email protected]
+49 241 80-94912
Thomas Pollok, M. Sc.
[email protected]
+49 241 80-94958
123
Student excursion to Hamburg
The metropolis Hamburg was this year’s excursion destination for the students of the
RWTH Aachen University. From May 24th 2010 to May 28th 2010 Hamburg was the
host for the paticipants of the excursion that consist of the chairs assistants, students and
Prof. Schnettler. During this week, many companies such as Airbus, RePower and Nexans
ranging from electronics to energy systems, made it possible for the students to recieve a
valuable insight into their field of activities whereas the range extended from electronis in
a plane to furnances of a steel mill.
Journey to Hamburg
At 9 am on Whitsun monday the excursion
headed to Hamburg. Despite this late departure, the bus ride went well since the students fell back to sleep immediatly. After
a lunch break the mood became more livley, because the free night schedule and the
room arrangements had to be discussed. At
about 5 pm, we arrived at the central located
A&O-Hostel in Hamburg.
ask questions. Afterwards, the guided tours
started in several groups. The factory was
introduced to us starting with the iron ore,
over the inspection of the furnance right up
to the manufacturing of the products such
as steel wire (Fig. 2).
124
Fig. 2: Steel mill by ArcelorMittal
Fig. 1: View onto Hamburg’s harbour
In order to compensate for the long bus ride,
the next item on the agenda was the traditional jogging with Prof. Schnettler. The
well known outer Alster was the ideal route.
Arcelor Mittal - steel mill
On Tuesday, we visited our first station in
Hamburg, the steel mill by the company
Arcelor Mittal. After a few presentations
and a film about the company and the functionality of the steel mill, we were able to
Very impressing were the extremly hot
and loud furnances, where the iron ore is
melted. Another imposing impression was
the furnance racking where the liquid material is drained for the further process.
E.On grid - 110kV-substation
After the exciting inspection of the steel
mill we drove to the countryside for a little recovery. We visited a 110kV substation
by E.On grid which is located in Norderstedt in northern Hamburg. While we had
coffee and cake in a restaurant, it was introduced to us how the establishment of a
substation is acomplished. Afterwards we
Student Excursion
in Kreetslag where the final assembly of
the A320 familiy and the structure and
equipment assembly of the A380 is located
(Fig. 5). Very impressing were the different dimensions of the aircraft families as
well as the high quality requirements even
on small planes which are checked twice.
drove to the substation, where we looked at
the construction from the outside as well as
the controlling and adjustment possibilities.
(Fig. 3).
Fig. 3: Group picture at the substation
At about 5 pm we went back to Hamburg
where we made acquaintance with the rushhour traffic for the first time. The rest of the
evening was used to get to know the inner
city of Hamburg as well as the Reeperbahn.
Airbus - Cabin Systems Test Center
and guided tour of the site
The third day of the excursion started very
early. Our first stop was at AIRBUS Operations GmbH in Buxtehude where the
parts of the development are placed. The
CSC (Cabin Systems Test Center) and the
Testrigs for the cabin electronic demonstrated how complex the technology of a
plane is and that everything is still based on
analog instrumentation. A walk through the
A380 was possible in a few parts at least.
Fig. 5: Excursion participants in front of the
A380
Vattenfall - power station Moorburg
After an exciting insight view into the aircraft construction we turned towards conventional power engineering and visited the
new construction of the power plant Moorburg (Fig. 6).
Fig. 6: Construction site of the power station
Moorburg
Fig. 4: Presentations at Airbus
After a very technical introduction, we visited the aircraft production from Airbus
After an introduction about the pitfalls of
building a new power plant such as including the construction of a fish ladder, we
got construction site friendly clothes and
started a very informative and also sunny
tour through the area. After a following
questions-and-answers session we headed
back to the inner city at 4.30 pm where the
125
126
students made a harbour tour or explored
the city by foot.
RePower - TechCenter and production managment
Dispite nightly activities everyone was right
on time and ready for departure on the
fourth day of the excursion. We drove
northward to the Repower TechCenter in
Osterrönfeld where we listened to presentations and technical lectures about wind
energy. After a refreshment we continued
our tour to the production of RePower in
Husum. In this factory, they produce the
nacelle and hub of the wind energy plant. It
was possible for the students to climb into a
finished nacelle to get an impression of the
extremly tight spaces inside. After the return to Hamburg, we headed to one of the
highlights of the excursion, the dinner with
Prof. Schnettler which took place in a small
restaurant on the Elbe.
Fig. 7: Excursion participants at Repower in Husum
Nexans and return to Aachen
The last day of the excursion started by
checking out of the hostel. We drove from
Hamburg to Hannover where we had our
last station at Nexans, one of the leading
companies in the cable industry. After a
very interesting technical lecture about the
power cable technology by Dr. Meurer,
the most interesting power cable projects
were introduced. After lunch we started the
tour through the factory where we could recover the previously learned in the production process. During the final questionsand-answers session the students were able
to ask their open questions.
At about 4 pm we went back to Aachen
where the students arrived tired but satisfied.
Organisation
[email protected]
+49 241 80-94916
Recreational Excursion
The trip on this year’s annual appreciation day on Wednesday, 18.08.2010 led us into the
Ahr Valley where we visited the former bunker of Germany’s federal government. As the
Ahr Valley is well known for its wineries we went to the Winzergenossenschaft Mayschoss
for a guided tour through the wine production process and wine tasting later in the day. In
the evening there was the traditional barbecue at Prof. Schnettler’s home.
Guided tour through the bunker museum
When we started our coach trip it was drizzling slightly. Nevertheless, 36 employees
of the IFHT were looking forward to an interesting day in the Ahr Valley which is approximately a one hour drive from Aachen.
The first stop led us on the traces of the Cold
War. During the 1960ties a bunker construction was build in former railway tunnels in order to offer protection for up to
3000 individuals for 30 days against the impact of a nuclear war over Germany.
part of the complex has been preserved
and has been converted into a museum
called „Dokumentationsstätte Regierungsbunker“. Divided into groups we went on
a guided tour though be bunker where the
temperature is 12°C during the whole year.
On the tour we were able to examine the
large number of former interior, machinery
and the security installations to learn about
the conditions of living and working in a
bunker building.
Appreciation Day 2010
127
Fig. 2: Security installations
Fig. 1: Bunker museum
Winzergenossenschaft Mayschoss
The bunker system consisted of tunnels
with an overall length of more than 15 km.
Offering accommodation for important representatives of the government it was intended to ensure that most functions of the
authorities would stay intact in the case
of emergency. With the end of the Cold
War, the so called „Ausweichsitz der Verfassungsorgane des Bundes im Krisen- und
Verteidigungsfall zur Wahrung von deren
Funktionstüchtigkeit“ became useless and
the deconstruction started in 1997. A small
Due to the continuing rain we skipped the
planned walk on the „Rotweinwanderweg“
and drove directly to the „Winzergenossenschaft Mayschoss“, a winery in the Ahr Valley where we got a guided tour through the
production facilities. Starting at the delivery gate for the grapes, we went along the
pressing station, tanks for fermentation and
storage and the facilities for bottling and labelling to learn the whole process of wine
production. Especially the possibility to
create individual labels for wine bottles as a
128
gift for jubilees, weddings or birthdays was
of high interest.
Fig. 3: Botteling station
Beside the modern production facilities
the winery also has a historic wine cellar where you can find good wines from
many vintages back to the 1950ties. We
were led though this cellar into a cosy
vaulted brick cellar room for the wine
tasting. Fortified by a typical lunch we
tried a number of six wines starting with
a light white wine over a Blanc de Noir
and finished with a smooth red wine. Our
guide gave not only explanations for every wine concerning the production process and the characteristics, he always hat
an interesting anecdote coming with each
wine. In the end of the day we learned
that there are only two individual types of
wine: Type one tastes well, type two not.
Fig. 4: Wine tasting
Barbecue at Prof. Schnettler’s house
We ended the day with a barbeque in the
garden of Prof. Schnettler’s family. The
rain finally stopped and most of our colleagues followed the invitation which has
already become a tradition for the IFHT’s
appreciation day. Everybody contributed
something to the buffet so there was beside the meat a huge variety of salads,
side dishes and desserts. Prof. Schnettler
lighted the fireplace as is became uncommonly cold for an evening in August and so
we got a cosy ending of an interesting day.
Fig. 5: Barbecue at Prof. Schnettler’s house
Organisation
Dipl.-Ing. Stefan Krengel
[email protected]
+49 241 80-93034
Service Portfolio
The Institute for High Voltage Technology has experience in various fields of high voltage
measuring and testing technologies and has appropriate facilities available to perform such
investigations. Various research and testing services as well as consulting can be offered.
Services
A focus of available studies is the determination of electrical and dielectric properties of insulation materials. The main scope
are testing procedures for insulation materials such as the determination of the breakdown field strength of insulation materials and the measurement of the dielectric
properties (dielectric permittivity ǫr , dissipation factor tan δ and surface / volume resistance) of material samples. Furthermore,
partial discharge measurements can be performed at the institute with voltages up to
200 kV at a noise level below 0.3 pC. If
a test requires special voltage forms such
as the lightning impulse test it is possible
to provide these test setups. All tests are
carried out according to recognized standards or to the customer’s requirements.
The institute offers the possibility to perform tests in a well defined climatic environment in order to identify the influence
of temperature and humidity. Apart from
the experimental test procedures, there is
also the possibility to commission the IFHT
with simulations. The focus in this area
is on CFD-simulations of physical problems (gas-, plasma- or fluid dynamics) as
well as on calculations of electromagnetic
fields. For comprehensive investigations on
certain tasks a collaboration within R&D
projects can be offered.
Test facilities
In addition to the classic high voltage test
laboratories a number of specialized laboratories and test facilities are available at the
IFHT:
• High voltage test lab for tests up to
400 kV AC or 800 kV impulse voltage
• High voltage construction kits for
modular assembly of test circuits
• Synthetic test circuits for the determination of the breaking capacity of
circuit breaker models with different
insulation gases.
Service Portfolio at IFHT
• Partial discharge test facilities with
test voltages up to 200 kV and a
noise level < 0.3 pC
• Several climatic test chambers
(15 m3 , -40 °C up to 140 °C), furnaces and thermal shock chambers
• Test benches and test chambers for
the analysis of aging behaviour (e.g.
salt spray test)
• Material processing laboratory for
insulation materials
In collaboration with the institute’s workshop, various test setups can be realised to
fulfill special test requirements.
Contact
Dr.-Ing. Ralf Puffer
[email protected]
+49 241 80-94950
Dipl.-Ing. Mathias Knaak
[email protected]
+49 241 80-94909
129
130
Test Center for Storage Systems and Smart
Grid Technologies
Future distribution networks will exhibit a long-lasting coexistence of decentralized generating units, conventional and modern consumers and the rising share of information and
communications technologies. Especially the integration of new energy converters, storage
systems and electric vehicles leads to new technical requirements, which are not known in
detail yet. For example examinations of equipment in different stress cases (normal and
overload), new protection concepts and contributions to system services by electric vehicles or batteries are largely unknown at present. In order to identify these requirements,
real measurements are just as important as simulations of those systems. For this, a new
laboratory for storage systems and smart grids is being built by RWTH Aachen University.
Introduction
The greater integration of renewables leads
away from conventional energy supply
structures to highly dynamic systems.
A secure energy supply in the future
needs intelligent network operations, taking bi-directional power flows, decentralized power generation, strong load fluctuations and the integration of electric vehicles into account. This kind of power system needs an intensive communication between electrical energy sources, consumers,
storage systems and network components,
in order to know the status of the whole system.
Fig. 1: Test Laboratory:
Aachen
Hüttenstraße 1-9,
There is a need to study technical requirements and concepts of grid management,
which such an energy system will entail. To
achieve this, grid impacts, protection concepts, as well as the behavior of components both in normal operation or in the
event of faults have to be researched sufficiently.
In order to carry out such metrological
tests and investigations a test bench for battery storage systems and Smart Grid technologies is currently being built by RWTH
Aachen.
Test Laboratory
The test bench, which is sponsored by the
Federal Ministry of Economics and Technology, is implemented by the Institute
for Power Electronics and Electrical Drives
(ISEA) as well as the Institute for High
Voltage Technology (IFHT). The collaboration in the domain of energy supply and
storage systems makes it possible to identify and evaluate problems, which depend
on both themes. This makes investigations
of specific problems of grids, storage systems and power units and their intersections
possible.
These are for example
• Interactions between distribution
networks and storage systems or
power units
• Behaviour of network equipment in
the normal and fault case
• The analysis of potentials for system
services in distribution networks (for
example the supply of control power
Test Center
• Effects of system services on storage
systems and power units (for example the impact on the aging of storage systems)
for electric vehicles, information and communication technology and network management systems can be achieved.
• Tests of new communication networks for Smart Grids
These and other investigations define specific requirements for information and communication technologies, power electronics, network technologies and network
management systems, which allow to derive technical and economic optimized operating strategies. Thereby, some principle
questions must be taken into account.
These are for example:
• How do accounting systems work
inside a distributed energy supply
structure?
• How can be ensured that services for
distribution networks do not lead to
disadvantages for the users of electric vehicles?
• What are the solutions for incentive
pricing models for electrical energy?
• Which safety requirements must be
delivered by communication networks (prevention of abuse and manipulation)?
Furthermore the Test Laboratory will play
a very important role in the standardization and certification of new concepts for
Smart Grid technologies and electric vehicles. The equipment allows standardized
tests for harmonic currents, voltage fluctuation and tests of interference resistance in
case of voltage dips. All components can
be tested in normal and fault case of distribution grids. Thus, both the development
as well as the verification of new grid codes
Fig. 2: Technical Structure of the Test Laboratory
Figure 3 shows the construction of the Test
Center at the RWTH Aachen. The location, used for the construction of the laboratory, has hall areas of about 1200 m2
and open spaces of more than 2000 m2.
On the outdoor areas there will be 22 single and three double laboratory containers
with technical equipment for the investigation of battery cells and battery packs under
different electrical and mechanical conditions. The equipment includes for example
circuits with automatic charging and discharging units for synthetic testing of battery packs. Moreover there are temperature
chambers (-40 - 130°C) and an impedance
spectroscope, which allows to analyze electric and dielectric material properties.
The laboratory for the investigation of new
structures of distribution networks will be
built up in the hall area. Figure 2 shows the
structure of the Laboratory.
There will be a grid simulator for generating variable voltage profiles for low voltage
networks up to peak power above 200 kVA
per phase. The system allows the measurement of harmonics and flicker, so that the
physical behavior of each test item can be
analyzed. There are many test procedures,
which can run automatically.
These test procedures allow the measurement of
by electric vehicles and distributed
power units)
131
F
NS
iNS
NS
iNS
NS
iNS
workshop
MS
NS
iNS
NS
Medium voltage switch gear
Local network substation
Intelligent local network substation
Network simulator
MS
LVRT - testsystem
MV - cable
LV - cable
Concrete channel
HV
MV
STAWAG
Fig. 3: Structure of the Test Laboratory
• Harmonic currents which are lead
back to the low voltage network (IEC
61000-3-2, IEC 61000-3-3),
• Voltage fluctuation and flicker which
are lead back to the low voltage network (IEC 61000-3-3),
132
office
iNS
NS
• Interference resistance tests against
voltage dips, short term interruptions
and voltage fluctuations (IEC 610004-11)
Current concepts show that communication between grid components, storage systems and power units will become more
important in the future. In order to test
these systems for distribution networks,
the Test Laboratory will have four ”intelligent” network substations of different
power (400 kVA, 630 kVA, 1250 kVA) and
suppliers. These substations are equipped
with electrical measurement and communication technology and allow reproducing
real low and medium voltage grids and the
test of different communication technologies (Ethernet, PLC, GSM...) for Smart
Grids. As with real network types in
densely populated areas, the substations are
connected in a ring network (Figure 4).
Each substation is equipped with six power
take offs, which can be used for any kind of
low voltage networks with cable lengths up
to two kilometers (NAYY-J 4x150 mm2 and
NAYY-J 4x240 mm2).
Furthermore there is test equipment to reproduce low voltage ride through tests for
medium voltage grids (up to 4 MVA at
10kV). Using an inductive voltage divider,
voltage dips can be realized for residual
voltages between 0% and 100% (up to several minutes). It allows the investigation
of components in the case of grid faults,
without negatively influencing the TSO’s
medium voltage grid. These kind of tests
were actually developed in order to verify
grid connection conditions for wind energy
plants (IEC 61400-21). The increasing development of decentralized electricity generation will expect this kind of examinations for future applications (for example
battery storage systems, large-scale PV installations, cogeneration units...).
Test Center
Medium Voltage Switchgear
STAWAG
Measurement
LVRT
Ring-1
Ring-2
110 kV/10 kV
Hall
LVRTContainer
Power Supply
1250 kVA
Power Supply
1250 kVA
400 kVA
630 kVA
630 kVA
1250 kVA
Grid Simulator
Battery Test Bench
630 kVA
Power Supply
Transformer
Station
Regen Unit
Flexible Connections
Fig. 4: Medium voltage network in the test bench
Contact
Dipl.-Ing. Bernhard Fuchs
[email protected]
+49 241 80-93038
Dr.-Ing. Stefan Federlein
[email protected]
+49 241 80-94959
Dipl.-Ing. Mathias Knaak
[email protected]
+49 241 80-94909
133
EEIM John Neal Award 2010
Andrey Mashkin, M. Sc. has received the
European Electrical Insulation Manufacturers’ John Neal Award 2010. The 5 000-euro
prize is given for outstanding investigation
accomplished in the field of electrical insulation materials and systems. His paper entitled "Analysis on the Electrical Properties
of Syntactic Foam under Various DC Field
Stresses"was judged by the award committee as the best application overall to meet
the award criteria for technical content,
practical application, originality and clarity of presentation. Investigation focuses
on the analysis of the electrical behavior
of syntactic foam, a new low-weight insulation material, which has been developed
in the co-operation between RWTH Aachen
University and Philips Medical Systems
(PMS).
Syntactic Foam
134
The design of several high voltage applications requires an exceptionally efficient
and compact insulation system. Especially in the rotating or mobile equipment
the requirements on light insulation materials cannot be fulfilled by conventional dielectrics. Syntactic foam, a special kind of
foam-like material, provides the best combination of compactness, light-weight and
high breakdown strength for this kind of applications. In syntactic foam the voids are
not made by blowing agent but exist inside
of hollow micro filler, which is embedded
in the polymeric basis. The Investigation
focus on syntactic foam, consisting of microscalic hollow glass microspheres, which
are mixed into an epoxy resin matrix. The
resulting compound is cured to rigid syntactic foam, which density is reduced by 40%
compared to epoxy resin. The mechanical and electrical properties of the syntactic foam can be tailored for each kind of
application by varying the filler size, type
and volume percentage. Fig. 1 shows
a Scanning Electron Microscopy (SEM)
picture of a cutting area of the material.
Fig. 1: SEM picture - inner structure of syntactic foam
Aim of the Study
The electrical Breakdown process in syntactic foam under short time ac and dc
field stress has been analyzed already at
IFHT in the previous investigations. The
determined high breakdown field strength,
which ranges 20-40 kV/mm for ac and dc
stress, enabled the use of syntactic foam
in high voltage applications. To broad the
dc application area of syntactic foam, several further processes in the material have
to be known. In many applications the high
electrical dc field is applied as a step function. This causes transient processes inside
the insulation system. Furthermore, during
long term stress an ageing process develops,
which has not been investigated jet. The
awarded study focuses on the further use of
syntactic foam in dc components and applications. For characteristic periods- at the
begin and during the continuous stress of
the material the field stress of each material
component as well as eclectic properties of
the whole material are analyzed. Finally,
the consideration of the microscopic field
distribution and the gained breakdown data
are used to extend the breakdown mechanism models. The award-winning paper
EEIM Award 2010
Download
The synopsis of the study is available for
download on www.ifht.rwth-aachen.de/
EEIM JNA2010 synopsis.pdf.
The Ceremony
Results overview
In the experiment, different types of syntactic foam are stressed with step function
voltage, causing transient processes to take
place inside the material. The materials’
conductivities are determined by measuring
the volume current. Additionally, the dependency of the breakdown field strength
on the transient properties of syntactic foam
is determined. The consideration of the microscopic field distribution inside syntactic
foam during the transient process is used to
analyze and extend the breakdown mechanism model of syntactic foam. The breakdown field strength in the long term test
is investigated for durations up to 5000 h.
The time to breakdown for field stresses of
16, 18 and 20 kV / mm is measured. The
combination of the determined conductivities provides all the required data to analyze
the field distribution in insulation systems
containing syntactic foam. The breakdown
properties of syntactic foam enable the long
term use of the material in high voltage
components. The determined values can
be used as design criteria to buildup lightweight and efficient insulation systems.
The award was presented on October 1,
2010 in Aachen on the occasion of the 90th
anniversary of Rogowski-Institute, in the
presence of the dekan of faculty, Award
Committee members, a representative of
the generator design team from Philips
Medical Systems, professors and IFHT
alumni. On behalf of his team, the award
winner thanked the award Committee for
the high honor.
Fig. 2: Award Committee members and awardwinning research team: f.l.t.r.: Berno
Habertür (EEIM), Michael Chapman
(EEIM), Anja Strauchs (IFHT), Andrey Mashkin (IFHT), Patrick Veluzat
(EEIM), Nobert Rudat (EEIM), Jörn
Podlazly (PMS), Prof. Armin Schnettler
(IFHT)
Contact
[email protected]
+49 241 80-94939
provides a basis for the use of syntactic
foam in the broad field of dc applications,
which ranges from high-voltage, direct current (HVDC) components to high voltage
DC test and lab equipment.
135
136
Staff of IFHT 2010
137

Contact - (IFHT), RWTH Aachen

Transcrição

Documentos relacionados

7809 datasheet

Product data sheet 6ES7321-1BH02-0AA0

Product data sheet 6ES7321-1BP00-0AA0

instruction manual - RC-Rob

Manson SPS-8250 Schaltnetzgerät

Issue 23 - January 2010

Renovation Strategies and Energy Calculation Tools

Valve actuator for 0...10 V or 3-position control

INGEPAC PQM300 flyer

Partial Discharge Detector, Type ICM compact