Investigation of non-uniform pollution performance on RTV coated bushing

Pollution induced flashover mechanism may pose a serious threat to reliable operation of high voltage bushings when exposed to various environmental conditions. Differences in the amount of pollution on the top and bottom surfaces in bushings may have great effect on surface flashover voltage and leakage current. Such pollution degrades the bushing and affects their electrical characteristics. In this paper bushing´s non-uniform pollution performance was studied. According to IEC60507 solid layer pollution method was used and laboratory based pollution performance test is conducted on bushing. Brushing method is adopted to coat the NaCl salt and kaolin mixture in different ratio with three equal intervals. Based on the artificial pollution test ESDD and NSDD levels are noted. Pollution is carried out for both normal bushing and RTV coated bushing. Based on test results it was found that the flashover voltage gets reduced when the T/B ratio increases and the performance of RTV coated bushing shows better results which inhibit the formation of continuous moist conductive layer.