Overvoltages and reignition behavior of vacuum circuit breaker

Vacuum circuit breakers (VCB) have excellent interruption and dielectric recovery characteristics, and can interrupt the high frequency currents which result from arc instability, superimposed on the line frequency current. The interruption of these high frequency currents is called virtual current chopping, and can lead to repeated reignitions when the breakers are opening, resulting in severe voltage escalations under certain network conditions. In order to estimate the probability of such transients, a mathematical breaker model has been developed in ATP / EMTP. The model incorporates the random nature of arcing time, current chopping, dielectric strength and the quenching capability of the breaker. The performance of forty-eight representative of breakers (four kinds of dielectric strength and four kinds of quenching capability with three different time ranges of the opening of the breaker) with specific network were analyzed and the results are presented in this paper.