Study of modification of electric field distribution in paper-oil insulation of transformer in the presence of copper sulphide

This study presents the FEM (Finite Element Method) results of electric stress analysis of copper sulphide contaminated paper insulation of transformers. This analysis is based on conductivity and permittivity changes that occur due to penetration of copper sulphide into paper. The differences in the two models based on conductivity and permittivity and their effect on electric stress distribution are discussed. Results show more variation in the maximum electric stress across the paper layers in the conductivity model than in the permittivity model.