A short circuit fault occurred in a GIS circuit breaker in Guizhou Power Grid. Through the disintegrationanalysis

it is found that the circuit breaker is not in the position of closing the arc-extinguishing chamber

the maincontact is not touched

and only the contact of the arc contact causes the contact resistance to increase

causes thecopper tungsten part of the serious heated

while the heat dissipation in the nozzle environment is not good

long-term heat accumulation

resulting in self-expansion of the arc-type contact after contact with the static arc contactpart of the gap

resulting in local arc ablation. When the ions generated by ablation accumulated to a certain concen-tration

the insulation properties of the gas chamber is destroyed

resulting in short-circuit between the tank and theshell. Through the trouble shooting and calculation of the faulty circuit breaker

it is found that the loosening of thebolts of the fixed transmission mechanism causes the circuit breaker to close in the wrong place

which leads to theshort circuit discharge of the circuit breaker. The causes of the looseness of the bolts are qualitative described andthe improvement measures of anti-looseness of the bolts are provided.