Very Light Pollution DC Flashover Characteristics of Short Samples of Polymer Insulators

Continuity of electric power transportation is an essential goal for power distribution companies to avoid revenue losses. Nowadays, the existing good insulation systems besides live-line maintenance procedures can secure this target. However, the pollution traces over insulating surface may cause the failure of power transmission systems. This research aims to find to what extent is the effect of very light pollution severity on the flashover performance of polymeric insulators under DC voltages. Two insulating materials are employed in this research, fiberglass reinforced plastic (FRP) and high temperature vulcanized silicone rubber (HTV-SiR). The sample's lengths are 130 mm and their diameters are 32 mm. The artificial pollution tests are performed according to the IEC 507 clean fog test method and the flashover voltage is determined by applying the up-and-down method technique. The results show that the pollution flashover voltage decreases as the pollution severity increases and is dramatically decreased as compared to the DC flashover voltage of clean samples. Moreover, the effect of equivalent salt deposit density (ESDD) on the 50% flashover voltage of the two materials is expressed as a power function. The pollution flashover voltage gradient of HTV-SiR samples is found to be better than that of FRP materials. It is highly recommended to wipe the hot sticks with silicone wiping clothes before and after the maintenance work to remove the very light pollution layers and provide the FRP surface with a layer of silicone which increases its flashover performance. These recommendations will promote the followed procedures for live-line maintenance to preserve crew's life from unintentional accidents.