Partial discharge phenomena in paper oil insulation under conditions of copper corrision due to sulphur in oil

The role of Mercaptans in causing copper corrosion is investigated and discussed in this paper. The performance of transformer oil samples has been investigated by conventional accelerated thermal-electrical ageing of paper oil insulation. Discharge measurements have been carried out using PD technique and variation of statistical parameters of discharges due to deposits of copper sulphide in between paper layers are reported and discussed. Study shows definite increase in number of PD events/second and a significant change in histogram patterns with increase in electric stress due to progressive migration of copper sulphide.