Relevant previous work in this area included estimating the current density distributions along polluted insulator surface, using surface charges simulation method [5]. Other studies simulated the leakage current while accounting for amount of salt in the contamination layer [6]. Other experimental studies were made on the effect of desert pollution on polymeric insulator [7,8]. In another study, leakage current was estimated using the FEMLAB software with different conductivities of contamination layer [9].
This paper aims to investigate the prime factor responsible for initiating insulator failure under power-frequency voltage, namely leakage current flowing through surface pollution.
Insulator simulation was carried out using an accurate 3-D ANSYS software program, which is based on the Finite Elements method. The program required higher performance computing and gave results with high accuracy. The ratings of transmission lines in Sinai are mainly 500 kV, 220 kV, and 66 kV. A typical two-shed insulator, which may be used on 220 kV power lines is used as a case study. Such leakage current distributions are determined with different sand grain thickness and with different sand conductivities. Realistic data are used, which are based on sand samples collected from Sinai desert near present and future transmission lines’ corridors and were reported by an earlier study [10]. In that study, the statistical distributions of sand grains size in the desert soil were acquired from random samples, where their salinity and subsequent conductivity were measured. Based on the calculated influence of sand grain size and salinity on the resulting leakage current, statistical distribution mapping was carried out to produce the overall probability density distribution of leakage current. The cumulative statistical distribution of leakage current was then employed to assess the risk of insulator failure.