Use of wavelet transform to analyze leakage current of silicone rubber insulators under polluted conditions

Leakage current is a very important parameter in the performance evaluation and monitoring of outdoor insulators. This paper presents experimental results of leakage current under different contaminated conditions of silicone rubber insulators. HTV silicone rubber sheets were utilized for tests and pollution was coated artificially in laboratory. The effect of temperature, humidity and pollution severity on leakage current of silicone rubber insulators were investigated. It was observed that leakage current magnitude increases with an increase in relative humidity, temperature, NSDD, and level of pollution severity. A discrete wavelet transforms (DWT) technique based on multi-resolution analysis (MRA) was used to study the time-frequency characteristics of leakage current. DWT-MRA technique can be used to detect frequency bands corresponding to different pollution severity levels and location of dry bands. These results can be used to predict dry band arcing activity on the surface of outdoor polymeric insulators.