Simulation of Partial Discharge under Impulse Voltage Waveforms

A drift diffusion model is used to investigate a PD between spherical electrodes coated by a dielectric material. The model geometry is an axisymmetric analog of crossed wire experiments which have been used in the literature to investigate PD activity due to impulse voltage waveforms. The simulation shows that discharges in crossed wire arrangements are likely to form surface ionising waves over the dielectric material covering the wires. This may allows the initiation of discharges at other locations where the electric field is high along the wires. The peak apparent current of this PD was found to be highly dependent on the applied voltage and exhibited a different pulse shape to PD inside spherical voids. The results suggest a significant factor behind the high magnitude discharges observed in impulse voltage waveform experiments may be the higher triggering voltage of the PD due to the impulse waveform.

I. Introduction

Measurements of partial discharge (PD) activity are a commonly used as a diagnostic tool to provide insight into the health of electrical insulation [1] . PD activity due to impulse voltage waveforms has recently received increased research attention [2 , 3] . The motivation for research this was the premature failure of electrical equipment that utilized these waveforms such as inverter fed motors [4] . PD measurements under impulse voltage waveforms in crossed-wire experiments have been shown to have higher apparent charge than sinusoidal waveforms [3] . PDs with a higher apparent charges are likely to cause more damage to insulation material and provide an explanation for the premature failure of the electrical equipment that uses impulse voltage waveforms. The reason for higher discharge magnitudes under impulse is thought to be that discharges regularly occur at voltages significantly above the inception voltage due to the quick rise times. It is also possible that in the crossed wire experiments high magnitude discharges can initiate other discharges leading to multiple PD events. The aim of this work is to provide insight into the discharge mechanisms of PD in crossed-wire experiments with the intention of providing qualitative insight into experimental measurements.