Diagnosis and Analysis of Partial Discharge Fault of 500kv Transformer

In this paper, a typical partial discharge failure of the 500kV transformer in the handover test stage is introduced. According to the local discharge signal characteristics under different pressure modes after fully eliminating external interference, it is preliminarily determined that local discharge has nothing to do with the insulation of the winding end of high and low voltage sides. Combined with the diagnostic test results after returning to the factory and the characteristics of no abnormal oil samples taken for many times, it is speculated that the fault point is not located in the winding, and there may be air gap discharge in the insulating parts. The results of disassembly inspection verify the inferences of local placement, confirm that local closed cavity of corrugated board between high and high voltage side windings leads to low energy discharge, and finally put forward suggestions to prevent similar defects of main transformer.