An experimental study of inhibited electrical discharges in air

Modern society demands a stable electricity supply, the reliability of which is partly determined by the dielectric strength of the outdoor high-voltage insulation systems. This paper concentrates upon the experimental study of one particular discharge phenomenon that occurs when such a system is subjected to rain, namely the inhibited discharge. This is a discharge whereby the energy input into the discharge channel is limited by the presence of a large series resistance in the discharge circuit; in practice water drops or runnels can act as this resistance. The experimental arrangement was a rod-to-plane electrode gap of up to 1 m subjected to a switching impulse. A water resistor (up to 4.7 M Omega) was placed in series with the rod electrode. The experimental results reveal the negative feedback characteristics of such an inhibited discharge; that is, as the discharge propagates, the discharge current charges the rod electrode and lowers the gap voltage. This negative feedback gives an increase in disruptive discharge voltage, a low discharge current and a prolongation of the final jump phase.