Mätning av krafttransformatorers nollföljdsimpedans
(2012) In CODEN:LUTEDX/TEIE EIE920 20121Industrial Electrical Engineering and Automation
 Abstract
 In the E. ON sponsored research project, Distibution LABoratory, at the Department
of Industrial Electrical Engineering and Automation at LTH the impact
of the increased move towards use of cables in the Swedish distribution
grid is examined. The project also built a model of a small distribution grid.
The model was used to simulate a Petersen coil earthed grid system. Petersen
coil earthing lowers the fault current by compensating the capacitive currents.
Since the share of cables in the mediumvoltage networks have increased so have
the capacitive currents. In order to minimize the fault current the inductive
compensation currents need to be increased. When calculating the compensation
current an uncertainty is found as an... (More)  In the E. ON sponsored research project, Distibution LABoratory, at the Department
of Industrial Electrical Engineering and Automation at LTH the impact
of the increased move towards use of cables in the Swedish distribution
grid is examined. The project also built a model of a small distribution grid.
The model was used to simulate a Petersen coil earthed grid system. Petersen
coil earthing lowers the fault current by compensating the capacitive currents.
Since the share of cables in the mediumvoltage networks have increased so have
the capacitive currents. In order to minimize the fault current the inductive
compensation currents need to be increased. When calculating the compensation
current an uncertainty is found as an unknown zero sequence impedance in
the Yynconnected transformers.
The purpose of this master thesis is to measure the zero sequence impedance
of the power transformers, investigate the transformer tank's impact on it, and
to develop a method that can be used for measurement on the fullscale transformers.
The work shows that the zero sequence impedance in Yynconnected transformers
is not infinite as many textbooks show. For phasetoground faults the zero
sequence magnetic flux is forced to flow into the air and the transformer tank
which greatly affects the size of the zero sequence impedance. As a consequence,
the zero sequence impedance should be measured on site and after installation
to obtain an more accurate result.
The measurements of the zero sequence impedance in transformers gives some
uncertainty that makes it difficult to draw definite conclusions. Measurements
made on fullscale transformers where raw data is saved would increase the
possibility to process the information and to exclude the influence of the Petersen
coil earthing used in the distribution model. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/studentpapers/record/3731788
 author
 Selimovic, Jasmin
 supervisor

 Magnus Akke ^{LU}
 Olof Samuelsson ^{LU}
 organization
 course
 EIE920 20121
 year
 2012
 type
 H3  Professional qualifications (4 Years  )
 subject
 publication/series
 CODEN:LUTEDX/TEIE
 report number
 5293
 language
 Swedish
 id
 3731788
 date added to LUP
 20130521 15:00:17
 date last changed
 20140904 08:29:54
@misc{3731788, abstract = {In the E. ON sponsored research project, Distibution LABoratory, at the Department of Industrial Electrical Engineering and Automation at LTH the impact of the increased move towards use of cables in the Swedish distribution grid is examined. The project also built a model of a small distribution grid. The model was used to simulate a Petersen coil earthed grid system. Petersen coil earthing lowers the fault current by compensating the capacitive currents. Since the share of cables in the mediumvoltage networks have increased so have the capacitive currents. In order to minimize the fault current the inductive compensation currents need to be increased. When calculating the compensation current an uncertainty is found as an unknown zero sequence impedance in the Yynconnected transformers. The purpose of this master thesis is to measure the zero sequence impedance of the power transformers, investigate the transformer tank's impact on it, and to develop a method that can be used for measurement on the fullscale transformers. The work shows that the zero sequence impedance in Yynconnected transformers is not infinite as many textbooks show. For phasetoground faults the zero sequence magnetic flux is forced to flow into the air and the transformer tank which greatly affects the size of the zero sequence impedance. As a consequence, the zero sequence impedance should be measured on site and after installation to obtain an more accurate result. The measurements of the zero sequence impedance in transformers gives some uncertainty that makes it difficult to draw definite conclusions. Measurements made on fullscale transformers where raw data is saved would increase the possibility to process the information and to exclude the influence of the Petersen coil earthing used in the distribution model.}, author = {Selimovic, Jasmin}, language = {swe}, note = {Student Paper}, series = {CODEN:LUTEDX/TEIE}, title = {Mätning av krafttransformatorers nollföljdsimpedans}, year = {2012}, }