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Effectiveness of Partial Discharge Test in Detecting Micro-Defects of Insulators in GIS

Micro-defects on the surface of gas-insulated metal-enclosed switchgear (GIS) insulators have always been a key factor restricting the reliability of GIS equipment. This type of insulation defect causes a small partial discharge amplitude, strong concealment, and high risk. It is a great challenge to use the partial discharge test to sensitively detect this type of defect. Therefore, it is urgent to clarify how effective the partial discharge test is for defects on the insulator surface. In this paper, a partial discharge test system was built in a 550kV GIS in accordance with the standard IEC 60270. Metal particle defects were set on the surface of the basin-type insulator, and the influence of the applied voltage and particle position on the partial discharge characteristics and PRPD patterns was studied. The results show that the partial discharge test has low effectiveness for insulation defects 140mm away from the busbar, and the inception and detection of partial discharges directly depend on the electric field distribution along the surface. This paper can provide guidance for the structural design of the insulator and condition monitoring of GIS.