Abstract: In this paper, an in-depth analysis of a switch trip event during the operation of a 330 kV line was carried out. After the inspection of the first and second devices, it was determined that the trip event was caused by the switch fault. After further inspection, it was found that the abnormal wear caused by the incomplete cleaning of the circuit breaker after run-in and improper application of grease led to the breakdown and discharge of the internal air gap. Finally, the circuit breaker insulation failure occurred. This paper puts forward some feasible suggestions and improvement measures for manufacturers in the link control and equipment owner acceptance test. These measures aim to ensure the safe and stable operation of the power grid, and provide useful experience and inspiration for the prevention and handling of similar incidents.