Calculation of transient electric field in vacuum interrupter under steep-fronted over-voltage

An transient circuit model for the vacuum circuit breaker switching no inductive motor is given and the steep-fronted over-voltage waves caused by chopping current are calculated. Discrete Fourier Transform (DFT) is introduced to decompound the step-Rant transient over-voltage. Several main frequency components are obtained, which are regarded as boundary excitation. The differential equations in complex form for calculating the transient field in vacuum interrupter are deduced. FEM is adopted IO calculate the transient electric field in the interrupter, Potential distribution curves at representative time are shown, which are compared with the one in the static field. The electric field intensity distribution curves are also given in this paper. Some distinguishing features of the transient field are discussed.