Abstract: Adding inorganic fillers to unsaturated polyester helps to greatly improve the electrical properties of polymer insulating materials according to the percentage of fillers concentrations and the types of fillers. Experiments and measurements have been performed to study and analyse the flashover voltage of unsaturated polyester with alumina trihydrate ATH and mica fillers with variety of samples lengths at different weather conditions. The probability of flashover to occur has been studied in this research. Flashover voltage value at dry unfilled polyester was 23.2 KV at 2.0cm sample length. Polyester with ATH filler at 60wt% concentration reached the greatest value of flashover voltage 42.3 KV at the same sample length. Polyester with mica filler achieved good results but the maximum percentage of mica filler concentration to be added was 40wt% with flashover voltage value of 38.4 KV.
Keywords: Flashover, Polymer, Insulators, Outdoor, High Voltage.