FIELD EXPERIENCE WITH OVERHEAD DISTRIBUTION EQUIPMENT UNDER SEVERE CONTAMINATION

A unique type of solid contamination on overhead distribution equipmen t was found in some regions of the Taiwan Power Company. The contamina tion was caused by the direct deposit of coastal sand dust during the winter season, An account of the field condition is given and the cont aminants are characterized to provide better understanding of the poll ution phenomenon. The sand contains high level of clay and salt that m ake it adhere to the overhead equipment and renders it highly conducti ve under moist conditions. High salt content not only caused accelerat ed metal corrosion but also high leakage current that led to pole fire s. The burning of crossarms, due to high leakage current, is a failure mode that has not been adequately addressed in the literature. Most p rior papers on pollution focused on contamination flashover. The leaka ge current measurements were carried out for overhead equipment using an artificial contamination test to quantify the effect of these uniqu e phenomenon, Some effective counter measures are described.