Electrical contact between a local discharge on an electrolytic solution and the solution surface [wet polluted insulators]

An electrolytic solution surface was used to simulate the surface of wet polluted insulators. A local discharge propagates on the solution surface when a voltage is applied to the surface. The electrical contact between the local discharge on the electrolytic solution and the solution surface was examined. The distribution of the current from the local discharge to the solution is estimated from the potential distribution measured with probes placed in the solution. The resistivity of the solution is varied from /spl sim/80 to 370 /spl Omega/ cm. Impulse voltages of 2/80 /spl mu/s, 10/800 /spl mu/s and 100/2500 /spl mu/s are used as the applied voltage. The peak value of the applied voltage was 1.05 to 1.4/spl times/ the 50% flashover voltage V/sub 50/ under each set of experimental conditions. As a result, it is found that most of the discharge current flows from the tip part of the local discharge, and the current from the local discharge column is considerably lower. Furthermore, the distribution of the current from the local discharge to the solution is found to be barely influenced by the resistivity of the solution, the peak value of the applied voltage, or the applied voltage waveform.