Improved simulation model for PD pattern in voids considering effects of discharge area

An earlier model for simulation of the phase-resolved pattern of partial discharge (PD) showed that the range of PD magnitudes could be produced by a variation of discharge area. Here we present a further development of that model. When the field in the void exceeds a certain value E/sub c/, PD occurs and extends along the void surface. In the PD propagation, the fields in the discharge paths and in the perimeter segments around the PD paths are reduced little by little by gradually changing the charge distribution. And the PD is terminated when the internal field in the PD path becomes lower than a critical value E/sub in/ and the field in the perimeter segments around the PD paths becomes less than another critical value E/sub p/. The simulation results became much closer to the actual PD patterns. And the large fluctuation of PD magnitude can be simulated even without consideration of any stochastic mechanisms. This model provides an approach to explain the transition of PD pattern in the aging process in terms of the change of surface condition.

1. Introduction

Monte-Carlo simulation of the phase-resolved PD pattern ( pattern) is an effective approach to disclose the PD mechanism. In conventional simulations [1], [2] which were based on the fundamental Whitehead model [3], it is assumed that the total field in a void after PD is reduced proportionally, and the PD magnitude is mainly determined by the field for PD occurrence and the residual field after PD. However, these kinds of models have difficulty explaining the large difference among PD magnitudes (even over 1000 times) in a void in insulating materials.