Analysis of the Breakdown of 500kV Circuit Breaker Caused by Foreign Body in Tank

High voltage circuit breaker is an important electrical equipment in the substation, and its safety status plays an irreplaceable role in the stable operation of the transmission line. When the high voltage circuit breaker fails, it will lead to an accident of the whole power grid, which will bring huge economic losses. In this paper, a circuit breaker fault caused by foreign matter in the tank is introduced in detail. Through the in-depth analysis and investigation of the factory data review, the detection of the supporting seat and tie rod of the insulation part, the analysis of the composition of the collected material in the factory, and the simulation of the field test, it is finally clear that the foreign matter at the piston rod is the root cause of the fault, and the foreign matter further leads to the electric field distortion. The metal at the lower end of the insulating rod is bridged by foreign body on the surface of the insulating rod by high voltage shielding, and the flashover discharge of the insulating rod occurs. Based on the above research process and results, some suggestions about the safe operation of circuit breakers are put forward.