A Study on Multiphase Flashover in Medium Voltage Line

Abstract

This paper discusses multiphase flashover in a Japanese 6.6kV medium voltage line. The multiphase flashover causes a short circuit in the line, and sometimes causes serious damages in power apparatuses and cables. Insulator voltage shows short-tail and stairwise waveform due to traveling waves reflected from neighbor poles and flashovers on the other insulators. A flashover on an insulator is determined using an integration method, which can consider an influence of voltage waveform on the flashover and can be used in the EMTP. Parameters such as grounding resistance, wavefront duration, power-frequency voltage and line configuration are examined to investigate the multiphase flashover in a medium voltage line. The simulation results suggest the insulator waveform significantly affect the multiphase flashover, and the integration method is an important tool for accurate lightning surge analysis with special reference to the multiphase flashover. This paper proposes an unbalanced insulation in power distribution line to reduce the multiphase flashover.