Effect of surface conditions on the electric field in air cavities

A numerical PD model was developed to obtain more insight into the understanding of the evolution of slot Partial Discharge (PD) activity. This model, in which multiple PD channels were simultaneously active, was used to evaluate the influence of the surface condition on the electric field distribution inside an air cavity typical of the one where slot PDs occur. It was observed that the insulation degradation induced by slot PD activity increases its surface conductivity, which in turn modifies the dynamic of the surface charges deposited by previous PDs and directly affects the electric field and the slot PD behavior itself. The experimental results of surface conductivity measurements and observations of physical changes in surface conditions obtained from previous laboratory experiments were used to feed the PD model. This paper reports the result of the electric field calculation in the presence of PD activity under different surface conditions.