In order to weaken more inrush current and overvoltage for capacitor banks and switchgears

we introduced a modified pre-strike measurement method of SF

6

circuit breaker

and put forward a synchronous closing scheme based on the pre-strike characteristics and the distribution of closing time. Moreover

we introduced equipment for dielectric strength characteristics measurement with a maximum output voltage of 400 k V

by which the dynamic breakdown characteristics of contact gap can be measured during the high voltage switchgear closing and opening once. Besides

we analyzed the dynamic breakdown characteristics of a 126 k V SF

6

circuit breaker by test. Based on the dynamic closing breakdown characteristics and the range of closing time

w

e made a synchronous controlling strategy. Theoretical analysis proves that

considering the characteristics above

the pre-strike voltage is reduced by 0.015 8

0

.336 2 per unit

and the range of the making time is reduced by 0.02

0

.35 ms. The strategy meets the design requirements well.