Online tan-δ measurement and investigation of insulation behavior during PD activity of PCCC in mercaptans contaminated transformer oil

Paper-oil insulation is widely used in transformers. It is reported that during life cycle of transformer, paper and pressboard insulation undergo deterioration because of increase in sulphur content in transformer oil. The reactive sulphur which forms copper sulfide and its deposition in paper-oil insulation system of in-service transformers results in degradation of insulation. The paper covered copper conductors (PCCC) in such oil medium leads to insulation failure. This paper presents tanδ behavior of insulation property of PCCC in transformer oil with reference to formation and migration of Mercaptans sulfur with online tanδ measurements.