Analysis of GIS Insulation Fault Characteristics under VFTO

Basin insulators are one of the rare faults with high probability in GIS equipment, especially the surface flashover of basin insulators, which poses a great threat to the safety of GIS operation. This article analyzes the II bus fault that occurred in the 220 kV GIS substation. Through the fault waveform and equipment damage, it was found that the fault was caused by the operating overvoltage generated when the circuit breaker was closed. To further analyze the fault, this article established an electric field simulation model to conduct electric field simulation analysis on the GIS bus under operating overvoltage and short-circuit grounding faults. The results indicate that the asymmetry of the bowl-shaped insulator structure exacerbates the occurrence of faults, and overvoltage and short-circuit grounding during operation lead to insulator breakdown.