This paper analyzes the statistic distribution of closing time of circuit breakers

of which different circuit breakers have much difference in distribution characteristics. Some is concentrated

and some is scatter. Data is required by testing hundreds of circuit breakers

which are at three voltage level

as 252 k V

363 k V and 550 k V

among 12 different models

at the substation site. It also can be found that

after a long idle

the first closing time is about 0

0

.6 ms larger than that of without idle

and the statistic distribution is less concentrated

which depends on the model of circuit breakers. This rule can be applied to phase-control ofcircuit breaker. The success rate of closing at targe

t pointcan be improved by 15%

2

5% when given a revised time to those circuit breaker whose first closing time obviously lager. That is of great guidance to optimize phase-control effect.