Influence of the properties of materials and the hydrostatic pressure on creepage discharge characteristics over solid/liquid interfaces

The present work is aimed at the characterization of discharges propagating on solid/liquid interfaces under ac voltages using a point-plane electrode arrangement. Different types of solid insulating immersed in mineral oil, are tested. The influence of the thickness of solid samples, the voltage, and the hydrostatic pressure on the length and pattern of creepage discharges as well as on the associated currents and emitted light are analyzed. It is shown that the final length, L_f, and the number of discharge branches, the associated current and en-fitted light are reduced when a hydrostatic pressure is applied. For a given pressure, L_f increases quasi-linearly with the voltage, whatever the solid insulating. L_f tends to increase with the dielectric constant of solid insulating.