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Experimental Investigation on Bridge Formation in Contaminated Transformer Oil

Experimental Investigation on Bridge Formation in Contaminated Transformer Oil
Experimental Investigation on Bridge Formation in Contaminated Transformer Oil
Oil is an essential insulating and cooling medium used in a vast range of high voltage equipment from cables to transformers and switchgears. Analysis on power transformer failures has revealed that insulation/oil contamination is a major factor, accounting for nearly 30% of the total failures. As a result there is a great deal of research interest in understanding the composition, insulating performance, ageing processes and breakdown mechanisms in such oils. In this project we are focussing on the effect particle contamination of transformer oil on electrical performance of high voltage power transformers. Transformer oil fulfils purpose both as electrical insulation and coolant. During the operation it contacts with metal, iron core and pressboard insulation inside a transformer. Contaminants such as metal filings or cellulosic residual can be formed in the oil, especially for transformers with aged paper insulation. During normal operation non-uniform fields are present within the transformer. These contaminants tend to move towards high field regions due to dielectrophoresis (DEP) forces and could form a bridge over a period of time. The bridge may potentially act as a conducting path between two different potentials within the transformer structure, leading to partial discharges or insulation failure. Initial experiment on pressboard cellulosic particles has demonstrated that pre-breakdown phenomena are closely related to the level of contamination [1]. Current work focuses on experiments with different sizes of pressboard particles under dc voltages. Three different levels of contaminants (0.0025, 0.0050 and 0.0075% by weight) have been used for the experiment. Current is also monitored whilst a dc voltage applied across a known contaminated oil sample. It has been found that at higher voltages the rate of bridge formation is increased along with an associated current increase.
10
Mahmud, S
37e36ae1-2092-474b-b362-7d6b10af0247
Chen, G
3de45a9c-6c9a-4bcb-90c3-d7e26be21819
Golosnoy, I O
40603f91-7488-49ea-830f-24dd930573d1
Wilson, G
25fbd90e-6949-481c-9e75-0d457003c839
Jarman, P
390aafbd-393e-4e20-bace-b4416e0dd456
Mahmud, S
37e36ae1-2092-474b-b362-7d6b10af0247
Chen, G
3de45a9c-6c9a-4bcb-90c3-d7e26be21819
Golosnoy, I O
40603f91-7488-49ea-830f-24dd930573d1
Wilson, G
25fbd90e-6949-481c-9e75-0d457003c839
Jarman, P
390aafbd-393e-4e20-bace-b4416e0dd456

Mahmud, S, Chen, G, Golosnoy, I O, Wilson, G and Jarman, P (2012) Experimental Investigation on Bridge Formation in Contaminated Transformer Oil. The Fifth UHVnet Colloquium, University of Leicester, Leicester, United Kingdom. 18 - 19 Jan 2012. p. 10 .

Record type: Conference or Workshop Item (Paper)

Abstract

Oil is an essential insulating and cooling medium used in a vast range of high voltage equipment from cables to transformers and switchgears. Analysis on power transformer failures has revealed that insulation/oil contamination is a major factor, accounting for nearly 30% of the total failures. As a result there is a great deal of research interest in understanding the composition, insulating performance, ageing processes and breakdown mechanisms in such oils. In this project we are focussing on the effect particle contamination of transformer oil on electrical performance of high voltage power transformers. Transformer oil fulfils purpose both as electrical insulation and coolant. During the operation it contacts with metal, iron core and pressboard insulation inside a transformer. Contaminants such as metal filings or cellulosic residual can be formed in the oil, especially for transformers with aged paper insulation. During normal operation non-uniform fields are present within the transformer. These contaminants tend to move towards high field regions due to dielectrophoresis (DEP) forces and could form a bridge over a period of time. The bridge may potentially act as a conducting path between two different potentials within the transformer structure, leading to partial discharges or insulation failure. Initial experiment on pressboard cellulosic particles has demonstrated that pre-breakdown phenomena are closely related to the level of contamination [1]. Current work focuses on experiments with different sizes of pressboard particles under dc voltages. Three different levels of contaminants (0.0025, 0.0050 and 0.0075% by weight) have been used for the experiment. Current is also monitored whilst a dc voltage applied across a known contaminated oil sample. It has been found that at higher voltages the rate of bridge formation is increased along with an associated current increase.

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More information

Published date: 18 January 2012
Additional Information: Event Dates: 18-19 January 2012
Venue - Dates: The Fifth UHVnet Colloquium, University of Leicester, Leicester, United Kingdom, 2012-01-18 - 2012-01-19
Organisations: Electronics & Computer Science, EEE

Identifiers

Local EPrints ID: 273123
URI: http://eprints.soton.ac.uk/id/eprint/273123
PURE UUID: 57725b60-10ff-4f1b-87fb-c65d013b785a

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Date deposited: 20 Jan 2012 14:26
Last modified: 30 Sep 2020 16:32

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