Field experience with overhead distribution equipment under severe contamination

A unique type of solid c o n t a m i n a t i o n on o v e r h e a d d i s t r i b u t i o n equipment was found in some regions of the Taiwan Power Company. The contamination was caused by the direct deposit of coastal sand dust during the winter season. An account of the field condition is given and the contaminants are characterized to provide better understanding of the pollution phenomenon. The sand contains high level of clay and salt that make it adhere to the overhead equipment and renders it highly conductive under moist conditions. High salt content not only caused accelerated metal corrosion but also high leakage current that led to pole fires. The burning of crossarms, due to high leakage current, is a failure mode that has not been adequately addressed in the literature. Most prior papers on pollution focused on contamination flashover. The leakage current measurements were c a r r i e d o u t for overhead equipment using an artificial contamination test to q u a n t i f y t h e effect of these unique phenomenon. Some effective counter measures are described.