Measurement of pollution level of 66 kV transmission line insulators

The presence of unwanted constituent on insulator surface of transmission tower plays an important ignition property for the likelihood of occurrence of flashover. In this paper, the pollution level of two aged insulators namely the longrod silicon rubber and the cap-and-pin glass insulators are measured. The results from the measurement shows that the Equivalent Salt Deposit Density (ESDD) of the cap-and-pin glass insulator, particularly near the pin is found to be 0.169 mg/cm² while the composition over the cap surface is 0.136 mg/cm². For the case of longrod silicon rubber insulator, the ESDD for both the pin and the cap are found to be 0.063 mg/cm² and 0.016 mg/cm² respectively. The outcomes from the ESDD measurements suggest that the cap-and-pin glass insulator string is severely contaminated with salt spray as compared to the longrod silicon rubber. Furthermore, a mathematical model of ESDD expressed in terms of salinity and temperature for both insulators is derived from multivariable regression method. The coefficients for both the cap-and-pin glass and longrod silicon rubber insulator are found to be 0.9984 and 0.9867 respectively.