Flashover across the surface of an electrolyte: arresting arc propagation with narrow metal strips

Abstract
A method of arresting the propagation of an arc across the surface of an electrolyte has been studied for its possible relevance to the design of high-voltage insulators for use in polluted locations. Experiments have been done using electrolyte contained in a flat trough and using, as powersource, a capacitor-resistor discharge circuit. Arc propagation and arrest have been photographed using a high speed ciné camera; corresponding voltage and current waveforms have been recorded with an oscilloscope. Arc arrest has been achieved by immersing, but not submerging, a long narrow strip of metal within the electrolyte across the flashover path. In some cases arc arrest occurred after the arc had been forced to propagate in a direction opposite to that which it would have taken had the strip not been present. A theoretical model has been presented to explain both such retrograde arc motion and arc arrest. It is based on the premise that the arc propagates in the direction which will maximise the current; key factors are the falls of potential at the anode and cathode, the resistance of the electrolyte around arc roots and the electric field intensity in the air ahead of the arc. Calculations are consistent with experimental observations. The findings are sufficiently encouraging to warrant further investigations on practical insulators.

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