Simulation of very fast transient overvoltage caused by disconnector switch operation in SF6 Gas insulated switchgear using multi-restrike arcing model

The common widely-used arcing model for the simulation of very fast transient overvoltage(VFTO) caused by switching operations of disconnector switching(DS) in SF6 Gas Insulated Switchgear(GIS) involves only one single spark model in which the superimposition of transients caused by the previous restrike due to the travelling wave reflection and refraction is neglected. In this paper, simulation of VFTO using multi-restrike arcing model was made for an opening and closing small capacitive current test circuit. The close operation of DS is elaborated as an example to explain the multi-restrike arcing model. Measurement of the VFTO is carried out for the test circuit by fiber-optic measurement system, and the comparison between the simulation and measurement shows the validation of the multi-restrike arcing model. The voltage of capacitive load obtained from the simulation coincides well with the step-wise shape voltage. From the simulation result, we can conclude that the restrike could occur at any phasic angle of the voltage and the peak value of overvoltage may not be at the initial breakdown time. Also some statistical data and influence factors related to the insulation analysis of GIS and adjacent equipment can be obtained from the simulation result.