Aiming at the abnormal problem of ultrasonic partial discharge live detection signal of 252 k V GIS equip-ment disconnector

the free particle defect in GIS equipment is determined

and the equivalent model of electricfield in disconnector is established. According to the characteristics of metal materials inside the equipment

thestress of different types of foreign particles are studied

and the trajectory simulation of different sizes of foreignbody particle under the physical field model are carried out

the existence of sheet metal particles at the bottom ofthe disconnector are analyzed and verified by disassembly inspection. The results show that the ultrasonic partial dis-charge detection can effectively detect the defects of foreign matters in the equipment. The status of foreign matters inthe equipment can be determined by using mathematical model stress analysis and physical field particle trajectorysimulation analysis. The millimeter copper metal particles at the bottom of the GIS disconnector determined by theanalysis are completely consistent with the disintegration results.