Modification of electric stress distribution in presence of copper ion in paper oil insulation of transformers

This study discusses the influence of copper ions on the electric stress distribution in paper oil insulation using Finite Element Method (FEM). The results have shown that the copper ions present in the paper oil insulation tend to modify the electric stress distribution more significantly at their site depending on their number and location. Further, an attempt is also made to explain the electric stress distribution in presence copper ions in copper sulphide contaminated paper layers and oil gaps in series with paper. The results of this study will be useful in assessing the increase in electric stress in transformer insulation due to simultaneous presence of copper ions in paper-oil and copper sulphide deposits on paper and across the windings.