Condition monitoring of 11kV porcelain pin insulator extracting surface current from total leakage current

Insulators are one of the most important components of the power system. Outdoor insulators get contaminated easily due to various kinds of pollutants. Leakage current flows even when surface is dry though magnitude is very low but this leakage current gets strengthened due to increase in humidity, light rain, fog, mist etc. It ultimately leads towards flashover which is highly undesirable. Therefore, condition monitoring of power system insulators is very much necessary. Leakage current monitoring is one of the prime techniques for insulator monitoring. Leakage current consists of both volume current and surface current. Only surface current is affected by external causes like contamination and humidity. Therefore, surface current is a more accurate indicator for condition monitoring. Using harmonic analysis method surface current is extracted from total leakage current. Phase angle analysis at different humidity conditions has been carried out for both total leakage current and surface current. From above mentioned analysis, it may be observed that a significant difference in phase angle may be obtained when only surface current is considered instead of total leakage current. Therefore, this paper gives rise to the possibility of using only surface leakage current for more accurate condition monitoring of insulator.