The electrically refusal opening of circuit breaker of GIS is a common defect in the operation. For identifying the cause of the fault

the research is performed with a type of operating mechanism with electrically refusal opening as the object. During the disassembly test of the faulty operating mechanism after returning to the factory

the technical means such as visual inspection

dimension measurement

hardness test are used to analyze and discuss the key parts

including the holding latch

of the opening and closing position from various angles in terms of the operating environment

material performance and transmission conditions. And a high-precision finite element model is set up for simulation verification. It is found from the faulty operating mechanism that one side of the mouting hole of the main level has machining errors

and the hardness deviates from the design requirements after heat treatment. The result indicates that the inner holes on both sides of the main level are asymmetrical

making the inner needle bearing and pin shaft slightly eccentric. Under the stress state

the needle bearing and the inner hole are deformed due to yhe influence of hardness difference between them. The combined effect of the above factors increases the static friction between the bearing and the inner hole

leading to a rise in the resisting torque on the openign system and causing resusal operation.