Polluted Barrier Effect on the Electric Field Distribution in Point-Plane Air Gaps under AC Applied Voltage: Based on Experimental Model

Abstract

The aim of this paper is to study the effect of the surface condition of an insulating barrier on the electric field distribution in point-plane air gaps with the presence of a space charge, under AC voltage. The pollution was modelled as a uniform conductive layer on the barrier surface. Electric field analysis was carried out by changing the conductivity, permittivity, and thickness of the pollution layer. Using the Finite Element Method (FEM), the geometric model has been implemented in COMSOL Multiphysics software. This method is used to solve the partial differential equations that describe the field with the presence of space charge. The electric field increases when the conductivity and thickness of the polluted layer increases. Uniform pollution on the side of the high voltage point greatly reduces the insulation quality of the barrier. In addition, a limit level of pollution, from which its minimal electric strength is equivalent to that of a conductive barrier, has been determined. This model has been validated by comparing with the experimental results of a point-barrier-plane configuration with a distance between electrodes equal to 5cm. The distribution of the electric field predicted by the numerical model is in accordance with the experimental results. The latter indicate that this model has a great contribution in the physics of discharges in the air under various polluted environments.