Insulation Fault Analysis Caused by Internal Metal Particles in 330kV GIS

Gas insulated switchgear (GIS) may develop defects internally during production, transportation, and installation, which can lead to partial discharges and consequently, failure. This paper focuses on an insulation fault caused by internal metal particles in a 330kV GIS. The composition of decomposition products and foreign objects inside the cylinder was analyzed using scanning electron microscopy and energy spectrum analysis. A multi-physics field simulation software, COMSOL, was used to establish an electric field simulation model and analyze the movement of metal particles in the cylinder and the fault mechanism. The analysis found that the cause of the accident was the vibration caused by the frequent operation of the circuit breaker near the fault point. This vibration moved the metal piece on the outside of the B-phase shield closer to the shield. Under the high electric field near the shield, the metal piece moved upward and ultimately caused a gas gap breakdown discharge. This discharge occurred because the local field strength exceeded the breakdown field strength, resulting in a fault. Based on this accident, solutions and preventive measures have been proposed to improve the operational reliability of this type of GIS equipment.