In response to the abnormal partial discharge defect of the gas insulated switchgear(GIS) circuit breaker in a 500 kV substation

ultrasonic and ultra-high frequency(UHF) methods are used for on-site live detection and positioning

while X-ray is adopted for defect verification. The video endoscope is employed to examine the distribution of foreign matters

and the scanning electron microscope(SEM) combined with energy dispersive spectrometer(EDS) is applied for component analysis. Combined with the full-process disassembly inspection after returning to the factory

the source of foreign matters is traced and the causes of defects are analyzed. The direct cause of the abnormal partial discharge is electric field distortion caused by foreign matter accumulation resulting from defects in internal mechanical moving parts of the GIS. The root cause is continuous foreign matter accumulation due to equipment design deficiencies and inadequate production process control

which ultimately leading to partial discharge. A four-in-one strategy incorporating equipment rectification

specialized inspection

enhanced monitoring

and process optimization is proposed for treatment

operation and maintenance prevention and control

providing a technical reference for fault diagnosis of similar equipment.