Research on the Mechanism of Extra Fast Transient Overvoltage of Gas Insulated Switchgear Equipment Based on the Tripping Event of 500kV Huangping Plant Station

In response to the bus and main transformer tripping accident triggered by the isolation switch not closing in place at 500kV Huangping plant station, this paper combines onsite inspection, returning to the plant for disassembly and simulation analysis to systematically reveal the fault mechanism. It is found that the disconnecting switch motor blocking module coil breakage leads to the dynamic and static contacts not closing in place, which triggers the gap discharge and extra fast transient overvoltage (VFTO), and finally causes the thermal collapse of the circuit breaker voltage equalizing capacitor. The cumulative thermal effect of VFTO on the voltage-averaging capacitor is verified by electromagnetic transient simulation, and improvement measures for equipment manufacturing, condition monitoring and emergency response are proposed, which provide a theoretical basis for the operation and maintenance and design optimization of Gas Insulated Switchgear(GIS) equipment.