Comparison of evaluation methods of the small current breaking performance for SF6 gas circuit breakers

Circuit breakers have to possess both the small current and the large current interruption capabilities. The need has been constantly increased to evaluate the current interruption performance without resort to the short-circuit tests to save time and expenses during the development of gas circuit breakers. The increasing reliability of the analysis schemes and the dramatically increased computing speed have made it possible to evaluate them from the computer simulation results to some extent. The objective of this paper is to estimate the small current interruption performance of SF6 gas circuit breakers and to compare the results from various methods. In order to evaluate the dielectric recovery strength of gas circuit breakers for small current interruption, two methods have been usually utilized. One is the empirical formula obtained from a series of tests and the other is the theoretical formula obtained from streamer theory. In this paper, both methods were applied to predict the small current interruption capability of model circuit breakers and were investigated in terms of the accuracy by comparing the simulation results with test ones.