A Ground Fault Analysis of 800kV Circuit Breaker after Closing

In view of an abnormal tripping accident of an 800kV SF6 circuit breaker occurred during the operation of S substation, this paper confirmed the fault circuit breaker through the analysis of the secondary protection action, the variation trend of fault recording voltage and current, and the components of SF6 decomposition. The damaged parts in the discharge process and the corresponding discharge trajectories were found by disintegration of returned to the factory. Based on the analysis of the material characteristics of the gas chamber after the fault, the explosion crack analysis of the preinsertion resistors(PIR), and the discharge trajectory analysis of ground fault, the electric field distortion caused by the foreign body inside the tank was confirmed as the cause of the discharge. At last, two kinds of foreign bodies were identified by particle flight path analysis and air gap electric field simulation analysis in the circuit breaker closing process, and corresponding solutions were given.