Flashovers of Suspension Insulators Due to Contamination

Flashover of suspension insulators on steel tower lines, traceable to an accumulation of dirt followed by a deposit of moisture, has been the source of numerous outages of high-voltage transmission lines. The aim of the investigation described in this paper was to determine means of increasing the insulation level of existing lines under fog and dirt conditions. Methods were developed to simulate, in the laboratory, the conditions of dirt and fog which cause flashover of insulators in the field. Using these methods, a study was made of the phenomena of flashover of contaminated suspension insulators. The benefits to be derived from lengthened strings and the superiority of special fog-type units with increased leakage distance were determined. Other means of reducing the hazard from dirt accumulation are suggested.