Analysis of a breakdown failure of 550 kV GIS circuit breaker

Insulation breakdown occurred in the transmission process of a 500kV GIS circuit breaker. Through the analysis of the differential protection action of the system, gas composition and X-ray detection, the disintegration of the fault gas chamber, and the investigation and analysis in the factory, it was concluded that the contact spring of the fault circuit breaker gas chamber was broken, causing discharge in the transmission process. With the continuous transfer of the internal fault arc, the gas in the cavity expands, and the ablative decomposition falls to the shield part on the side of the moving contact through the support base porosity and generates discharge to the ground at the exit of the circuit breaker housing. The analysis and research of this accident can provide a reference for similar fault treatment and analysis in the future and the improvement of circuit breaker manufacturing and assembly process.