Voltage-time characteristic of electrical breakdown in SF6

V-t characteristic of impulse and switching surge breakdown in SF6is studied on various gaps. The characteristic is categorized into three patterns depending on the configuration of the gap and gas pressure. The properties of the V-t characteristic in these patterns are generalized as a semi-empirical formula which will be useful in the quantitative evaluation of the insulation coordination and the abnormal voltage protection of SF6gas insulated power equipments. The gap conditions in which those patterns of V-t characteristic are observed are also discussed in the Appendices.