Electric Fields and Electrical Breakdown

This chapter discusses electric field theory and the concept of electric breakdown of gaseous, liquid and solid insulating materials. Partial discharges (PD) cannot occur unless there are high electric fields on the surface of, or within, the electrical insulation system that can lead to a localized electrical breakdown of the insulation. Thus, to understand the physics of electrical breakdown and PD, the electric field in the insulation system must first be measured or calculated. Electrical breakdown occurs when a conductive path through the insulation system connects at least two electrodes at different potential, for example between a high‐voltage conductor and ground, or between conductors in different phases. The dielectric strength is defined conventionally as the electric field at which breakdown occurs in a parallel plate sample with thickness under a uniform electric field.