Numerical analysis of the external insulation of outdoor vacuum circuit breaker under lightning impulse voltage

In this paper, a new mathematical model combining electric field and current,field is introduced and finite element method is adopted to calkulate the transient electric field of the external insulation of the outdoor vacuum circuit breaker. Dielectric medium with permittivity E and conductivity y under lightning impulse is taken into account. The response caused by lightning impulse voltage i s expressed by Duhamel integration, which is regarded as the boundary excitation of solved region. Under lightning impulse voltage, the potential distributions of external insulation at representative time are shown. Electric intensity distribution curves on external insulation surface with respect to time are also calculated in this paper. The maximum of intensity on external insulation surface is also given, which are compared with the one in the static field. Some distinguishing features of the transient field arc also discussed. It is essential for vacuum circuit breaker insulation design.