Abstract: Influenced by manufacturing technology, assembly process, operating environment and other factors, the gas-insulated switchgear may have SF₆ gas leakage, partial discharge and other faults during operation. This paper introduces the leakage discharge of the expansion throttle chamber of a 220 kV gas-insulated equipment, and the tripping of the 220 kV bus differential protection. Through this accident analysis, it has certain reference significance for the operation and maintenance of GIS equipment.