Moisture effects on AC dielectric strength and partial discharge inception voltage in natural monoesters

摘要

It is essential to analyse the dielectric performancein a humid environment of insulating liquids of plant origin,considered as alternatives to mineral oil (MO) which is notenvironmentally friendly. This paper focuses on the effects ofdifferent moisture levels on the dielectric strength and partialdischarge initiation voltage of two natural monoesters, basedon castor oil (CO) and palm kernel oil (PKO), and MO. Thedifferent samples were moistened with a glycerol solution,then sealed and stored for 12 days to allow further diffusion ofmoisture into the samples. Dielectric strength was statisticallyevaluated from IEC 60156. Partial discharge inceptionvoltage (PDIV) experimentwas performed in conformitywithamodified IEC 61294 purpose at ambient temperature. Basedon the experimental observations, the moisture has differentbehavior on dielectric strength and PDIV of insulating oils.Monoesters have a better withstand to water contaminationthan MOs in power transformers.