Abstract:

When the disconnector in SF₆ gas insulated switchgear (GIS) is used to open and close the busbar, a very fast transient overvoltage (VFTO ) with high amplitude and extremely fast rise rate is generated, which threats the insulation of GIS and adjacent equipment.The testing circuit of an 800 kV GIS disconnector switching on and off busbar is selected as the research object.The electromagnetic transient program (EMTP/ATP) is used for modeling and simulating, the Mayr arc model is used when the disconnector is ignited, and its influence on VFTO is analyzed.The voltage waveforms of the disconnector, circuit breaker side disconnector and transformer side disconnector considering the Mayr arc model are obtained,compared with the VFTO considering the time-varying resistance model. Discrete Fourier analysis of VFTO waveform is carried out to obtain the variation characteristics of overvoltage frequency and amplitude, and the research results provide a reference for GIS insulation design.

Key words: SF₆ gas insulated switchgear (GIS), very fast transient overvoltage (VFTO), Mayr arc model, Fourier analysis