Study on influence of oxidation on static electrification in transformer oil

In oil-immersed transformers, static electrification phenomenon is caused by insulating oil flowing on solid insulator such as pressboard (PB). In Japan, as a countermeasure, 1, 2, 3-benzotriazol (BTA) is used to suppress static electrification. But, recent years, it has been reported that static electrification phenomenon increases with aging owing to oxidation of insulating oil, operation history of transformers with overhaul, and so on [1]. This paper deals with the verification of BTA effect on the increase of electrostatic charging tendency (ECT) due to aging, and evaluation for the influence of air exposure on static electrification during overhaul using the aging oil from 500 kV transformer by performing overhaul process according to actual operation and accelerated aging test.