Abstract: Paper–oil insulation is widely used in transformers. The reactive sulfur forms copper sulfide and dispersing in oil causes the reduction in insulation of the transformer. It is reported that during life cycle of transformer, paper and pressboard insulation undergoes deterioration mainly because of increase in sulfur content in transformer oil. The types of reactive sulfur that are present in transformer oil are Mercaptans (2-MBT) and di-benzo-di-sulfide (DBDS). The Ř-t-N distribution is a popular choice for PD representation as the discharge magnitude is associated with the state of insulation. Representations based on the charge magnitude are susceptible to influence of the measuring system, discharge and equivalent characteristics. On the other hand, the Ř-t-N representation offers much flexibility hence this method is chosen to compare the performance of PCCC under the influence of different sulfur contamination.

Keywords: PD, Sulfur corrosion, paper-oil insulation, Mercaptan sulfur, DBDS sulfur.