Some properties of surface discharges

Electrical discharges can occurring in a gas, liquid or a vacuum in close vicinity to a solid dielectric surface. Such a discharge is known as a surface discharge. As a result of the proximity of the discharge plasma to the surface considerable degradation of the solid dielectric surface can occur. This can subsequently lead to electrical failure and thus studies of surface discharges can be of importance to the electrical supply industry. Surface discharge phenomena have been examined using a needle-plane electrode configuration with the dielectric material partially filling the gap between the electrodes. Relatively large applied voltages are required to generate surface discharges of moderate length. By pre-charging the solid surface the applied voltage required to initiate discharge activity across the surface may be considerably reduced. Indeed the applied Laplacian field may well be below the limiting value of the electric field for the gas.