The paper describes mechanisms of surface discharges development on ceramic, glass with silicon rubber cover and between polymer and varistor. Underlying these mechanisms are these materials electrical strength and behavior. The type of discharge on surface or near dielectric surface depends on material on to which the electricity is to be discharge, type of both space charge and charge generated on surface, as well as on type of voltage and shape of electrodes. Flashover voltage of both insulating and power protecting systems can be increase by applying of semi – conducting covers which will carry away the generated surface charge and uniform the distribution of electric field on material surface. The above thesis was confirmed by DC, AC and high impulse voltage tests.
When it comes to glass covered with silicone rubber the surface discharges develop more readily on the glass side, what was recorded on pictures.