Study on the effect of moisture ingression into metal oxide surge arrester using leakage current analysis

This paper describes the effect of internal moisture content of a porcelain housed metal oxide surge arrester(MOSA) on it's operating characteristics. Moisture ingression into arresters internal region is one of the most important degrading external factor which need to be monitored carefully after years of it's operation. So, leakage current analysis is performed on a fresh 11kV ZnO surge arrester to track it's degree of degradation due to internal moisture. Accelerated moisture ingression is done by keeping MOSA immersed into hot water for almost a month. It is already been well established that resistive component of leakage current is more sensitive to any kind of degradation of active ZnO element than total leakage current. Therefore, variation of resistive leakage current and it's different harmonic components with inner moisture content have been investigated and explained in this paper.