Influence of overvoltage waves on the development of partial discharges

Abstract

A theoretical study of the development dynamics of partial discharges in defects in cable insulation of medium voltage networks in the presence of an overvoltage wave has been carried out. Simulation modeling of the development of partial discharges was performed on the basis of a model with three capacitors, supplemented by a model for the appearance of a seed electron. A single-phase short circuit to earth with several breaks in the electric arc was the source of the overvoltage wave. Simulation modeling showed that the number and power of partial discharges significantly increased over the period of the fundamental harmonic. The amplitude of the periodic component of the transient process was already enough to recharge the defect for large insulation defect and it is the highest harmonic that becomes decisive in the formation of partial discharges. This fact may be one of the explanations for a possible trend in medium voltage cable networks, where a failure on one cable is followed by a group of subsequent failures in nearby cable lines within a few days.