The support insulator is one of the components with high probability of failure in GIS equipment, and the along-surface flashover and air gap defects are serious threats to the safe operation of GIS equipment. The paper proposes a method of GIS internal defect diagnosis and location based on UHF signal. Combined with the online monitoring system, the paper introduces its application process in the detection and locating of the air gap discharge of the GIS support insulator in operation. The partial discharge type is distinguished by the phase resolved partial discharge pattern recognition, and the locating of partial discharge is based on the time difference method. The disassembly analysis of GIS equipment verifies the effectiveness of the above method used by the GIS online monitoring system and avoids further development of partial discharge leading to unplanned busbar outages or serious accident. The application characteristics of partial discharge technology are analyzed in conjunction with the case study to provide reference for insulation monitoring of GIS equipment.

gas-insulated switchgear (GIS),partial discharge,ultra-high frequency,Partial Discharge (PD) location,partial discharge diagnosis