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Reference: ISH2015_114

ISH Collection

Electrical Insulation Performance under HVDC and Polarity Reversal Conditions in Oil-Immersed DC Converter Transformers



In HVDC power systems, an oil-immersed AC/DC converter transformer is the main apparatus used in their composition. As for the development of these converter transformers, it is necessary to enhance their electrical insulation performance while taking specific DC behaviors such as DC electric field distribution, DC charge accumulation and DC polarity reversal characteristics into consideration. In this paper, the electric field distributions in an oil-impregnated pressboard composite structure, which models the structure in actual DC converter transformers, were calculated under AC, DC-steady state and DC-polarity reversal conditions, by analysis with the Finite Element Method (FEM), and their electrical insulation performances were investigated and discussed. The results showed that it is very important to arrange the pressboard barriers well in oil to control the equipotential lines without generating any additional electrical stresses. In addition, it was concluded that the most critical condition for breakdown strength could be the DC-polarity reversal condition and the related conductivity ratio of the oil and pressboard.

File Size: 1,3 MB

Year: 2015

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