Analyzing of Polymeric Insulators Aging under Humidity and Pollution Condition using Leakage Current, Flashover Voltage and SEM Analysis

Polymeric insulators in overhead transmission lines are under different stresses such as: electrical, environmental and mechanical stresses. These factors cause the insulator aging and the increase of leakage current and also the decrease of flashover voltage. When layer of environmental pollutants is formed on the insulator surface and combined with atmospheric moisture, low impedance path created on the surface that prone to more leakage current and also less flashover voltage. This event makes the fault in the insulators especially in aged insulators. In this paper to investigate the effects of aging on the leakage current and flashover voltage of polymer insulators under contamination and humidity, four different types of 20 kV polymer insulators put inside the artificial aging chamber for 1,000 hours. Then every two weeks one of each type of insulators was removed from aging chamber and flashover voltages and leakage current signals were measured and the obtained results were evaluated. In addition for monitoring the insulator surface state at different stages of aging, scan electron microscopy (SEM) was conducted and the results show that aged insulators have more pores and with weaken hydrophobic properties, leading to poor performance of insulator and increase the leakage current and decrease the flashover voltage.