Relation between leakage impedance and equivalent salt deposit density on an insulator under a saltwater spray

The degree of pollution of an insulator polluted rapidly under a saltwater spray is observed by measurement of the leakage current, which flows between electrodes fixed on the surface of the insulator, under 30 V ac voltage. Long rod insulators were used as samples. The relation between the leakage impedance and the equivalent salt deposit density (ESDD) of the insulators was obtained under several experimental conditions. As a result, the following was found (1) the effect of the wind velocity on the insulator is small, and is especially small when the distance between the electrodes is short, (2) the effect of the distribution of the saltwater drops on the insulator is small, and (3) the leakage impedance does not depend on initial dryness of the insulator surface (and the conductance is low) before the saltwater spray. It is important that the ESDD be above a certain value, and that the distance between the electrodes be short. Furthermore, it was shown that ESDD can be estimated fairly exactly from the leakage impedance.