4 1-Modeling Simulation and Experimental Verification of Fast and Very Fast Electromagnetic...

University of Applied Sciences of Eastern Switzerland

Jasmin Smajic, Roman Obrist, Martin Regg, Thomas Franz

Modeling, Simulation, and Experimental Verification of Fast- and Very Fast Electromagnetic Transients University of Applied Sciences of Eastern Switzerland (HSR) Institute of Energy Technology (IET) Oberseestrasse 10, CH-8640 Rapperswil, Switzerland [email protected]


Outline

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n Introduction

n Electromagnetic transients in power system components

n HF modeling and simulation of power and distribution transformers

n Lightning impulse (LI) overvoltages and fast transients

n HF modeling and simulation of gas insulated switchgears

n Very fast transients

n Conclusions


Introduction

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n Electromagnetic transients in power system components [1]:

n Origin: sudden change in the steady state values of voltages or currents (lightning stroke, system malfunction, normal operation switching operation, switching operation to clear a fault, etc).

n Duration, i.e. frequency range:

n LI-overvoltages: according to the IEC standard 1.2s/50s (


Introduction

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n LI- and fast transients in power and distribution transformers [2]

n HF transformer modeling and simulation

n Experimental verification of the results

n Very fast transients in gas insulated switchgears (GIS) [3]

n Full-Maxwell modeling and simulation of VFTs in GIS

n Mitigation of VFTs in GIS

n Experimental verification of the results [2] J. Smajic, T. Steinmetz, M. Regg, Z. Tanasic, R. Obrist, J. Tepper, B. Weber, M. Carlen, Simulation and Measurement of Lightning-impulse Voltage Distributions Over Transformer Windings, IEEE Transactions on Magnetics, Vol. 50, No. 2, Article#: 7013604, February 2014. [3] J. Smajic, A. Shoory, S. Burow, W. Holaus, U. Riechert, S. Tenbohlen, Simulation Based Design of HF Resonators for Damping Very Fast Transients in GIS, IEEE Transactions on Power Delivery, Vol. 29, No. 6, pp. 2528-2533, December 2014.


LI- and Fast Transients in Power and Distribution Transformers

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1.2s / 50s impulse:



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1.2s / 50s impulse: = / ()



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Boundary initial value problem (BIVP): (1/ )+ 0/+ 00/(/)=0, (,,) 3 =0, (,,) 2 (1/ ) 0//( )= 20/( 0), (,,) 2 =0, =0, (,,) 3

Accurate Full-Maxwell Approach

J. Smajic et al., Transient Full-Maxwell Computation of Slow Processes, in Scientific Computing in Electrical Engineering (SCEE 2010), Mathematics in Industry, Vol. 16, Part 2, pp. 87-95, Springer Verlag, Berlin, Heidelberg, New York, 2012.



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Vector Finite Element Method (FEM) is required for this analysis.

Linear vector tetrahedral element: (,,,)= (,,) ()




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10





11





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[2] J. Smajic, T. Steinmetz, M. Regg, Z. Tanasic, R. Obrist, J. Tepper, B. Weber, M. Carlen, Simulation and Measurement of Lightning-impulse Voltage Distributions Over Transformer Windings, IEEE Transactions on Magnetics, Vol. 50, No. 2, Article#: 7013604, February 2014.

A 4-turn winding model as an example:

Novel Approach: Winding Modeling in Its Full Complexity



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Structure of the equation system:

C-matrix (left) and L-matrix in logarithmic scale:

Novel Approach: Winding Modeling in Its Full Complexity



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Example: dry-type 1600kVA VCC transformer.



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Example: dry-type 1600kVA VCC transformer.

Voltage distribution E-field


Very Fast Transients in Gas Insulated Switchgears

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1100kV AC Jingman Substation in China



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Shaft

Moving contact Fixed contact

Insulator Additional shield

Circuit breakers

side

Transformers side

0 0.01 0.02 0.03 0.04 0.05 0.06

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

Voltage is high enough to ignite a spark

Floating potential conductor Network voltage

Contact separation



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[4] J. Smajic, W. Holaus, J. Kostovic, U. Riechert, 3D Full-Maxwell Simulations of Very Fast Transients in GIS, IEEE Transactions on Magnetics, Vol. 47, No. 5, pp. 1154-1517, May 2011.

( ) ( )( )

( )

00 0 0

00

1

2PORT

PORT

i i r ir PORT

iPORT

A AA N dV N dV N n n A dSt t t Z t

N n n E dSZ

+ + =

=

r rr rr r r r rr rr r

Weak form of the BIVP:

Linear system of equations:

[ ] { } ( ) { } { } { }2

2 ( ) [ ] [ ] ( ) [ ] ( ) ( )A A

T t R Q t S A t f tt t

+ + =



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20




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HF resonator:

J. Smajic, W. Holaus, M. Seeger, F. Greuter, A. Iordanidis, U. Riechert, Conductor Arrangement for Reducing Impact of Very Fast Transients, European Patent Office, Application/Patent No. 11174464.5 1231, Date of filing: 19.07.2011.



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[3] J. Smajic, A. Shoory, S. Burow, W. Holaus, U. Riechert, S. Tenbohlen, Simulation Based Design of HF Resonators for Damping Very Fast Transients in GIS, IEEE Transactions on Power Delivery, Vol. 29, No. 6, pp. 2528-2533, December 2014.

Experimental verification:


Conclusions (Transformers)

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The suggested method is mathematically well founded, stable, accurate and efficient.

Due to its generality the presented method can be used in case of very complex windings (transformers for 36-pulse rectifiers, for example).

The disagreement between the simulations and measurements in terms of both the oscillation frequencies and the voltage peaks stays below 20%.

Considering the complexity of the analysis this accuracy is sufficient for the daily design.


Conclusions (GIS)

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Full-Maxwell 3-D simulation of the VFTs in GIS are feasible. The results of the 3-D VFT simulations improve our understanding of the

phenomenon.

The presented simulations reveal critical places of the given GIS design. The 3-D time-domain VFT simulations enable parameter studies and design

optimization.

Simulation based resonator design was confirmed by experiments. Efficiency of the resonator at damping the VFTs was confirmed by

measurements.

All simulation models are wrong, but some are useful!

4 1-Modeling Simulation and Experimental Verification of Fast and Very Fast Electromagnetic...

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