186 / 2018-08-30 12:19:40

Influence of Dry Band Configuration on Arc Inception and Flashover Voltage of Silicone Rubber Outdoor Insulators

dry bands,outdoor insulators,silicone rubber,flashover characteristics,inception voltage,pollution

During service conditions, outdoor high voltage insulators are exposed to various types of stresses (electrical, thermal, mechanical, environmental). Pollution deposited on the surface of outdoor insulators lead to changes in dielectric strength of insulators. The pollution deposited on the insulators contains soluble and non-soluble contaminants. During rain, fog or mist, the soluble contaminants of pollution dissolve in water and provide a conductive path to the flow of current. Due to Joule heating, some parts of the insulator surface become dry resulting into dry bands. Dry band formation along the surface of outdoor high voltage insulators is a very important phenomenon. The formation of clean and dry bands effects the performance of outdoor insulators. To determine the exact location and configuration of dry bands on the insulator surface required sophisticated software and hardware and is not a feasible solution.
In this paper, experiments were conducted to investigate the effect of dry band location and configuration on two important parameters of outdoor insulators: arc inception voltage and flashover voltage. Two types of dry band configuration are considered: vertical and horizontal dry bands. Furthermore, the effect of single and multiple dry bands is also investigated. HTV silicone rubber samples are prepared artificially in laboratory using modified IEC 60507 standard.
All tests were conducted in controlled environmental conditions inside a climate chamber. It was observed from the obtained results that the arc inception and flashover voltage significantly change when dry band forms on the insulator surface. Furthermore, with increase in number of dry bands, flashover strength increases. These results may be helpful for scientists and engineers in the design and selection of outdoor polymeric insulators for polluted environments.