Voltage-time characteristic of electrical breakdown in SF6

V-t characteristic of impulse and switching surge breakdown in SF
6
is 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 SF
6
gas insulated power equipments. The gap conditions in which those patterns of V-t characteristic are observed are also discussed in the Appendices.