Influence of partial electric arc on the contamination degree monitoring system in view of leakage current

The leakage current of the insulator during wetting process can be converted to the surface conductivity by combining the operating voltage and insulator shape. Furthermore, the salt deposit density (SDD) of the insulator with natural contamination can be calculated and the contamination degree can be evaluated. However, due to the heating effect of the leakage current, some dry bands could be generated on the insulators' surface during the wetting process, which makes the leakage current appear smaller than the condition when the insulator is moist completely. In this paper, leakage current trends of two different types of insulators during the wetting process were measured and the surface conductivity was calculated. The test results showed that, due to the influence of the partial electric arc near the pin, the surface conductivity deduced from the leakage current was smaller than that of the actual surface conductivity of the contamination layer, but for certain types of insulators, there was a relatively fixed correlation between them.