Influence of system fault parameters on breaking performance of vacuum circuit breaker: modeling and simulation

A black box model of vacuum circuit breaker is established based on diffuse vacuum arc interruption. With the current ZCP(Zero-Crossing Point) as demarcation point, the arc voltage is modeled for the arcing period and its related coefficients are determined according to the test data. The post-arc current is modeled for the post-arc dielectric recovery period based on the Langmuir probes theory. The simulative results for different rising rates of TRV(Transient Recovery Voltage) are consistent with the experimental results. Based on the built models, the equivalent breaking capability discount factor of vacuum circuit breaker caused by the direct current component of short circuit current is evaluated by different methods, which shows that, the arcing energy method is more rigorous than the transferred electric charge method while the latter is more rigorous than the current RMS value method. The post-arc conductivity is used to represent the dielectric recovery degree and results show that, the rising rate of TRV mainly influences the post-arc dielectric recovery rate after 1.5 μs while the decay rate of short circuit current prior to current ZCP only influences the initial post-arc dielectric recovery rate. The influencing rules of some system fault parameters on the breaking capability of vacuum circuit breakers are given.