Investigation of saturation moisture in the PD behavior in the biodegradable ester oil

Abstract

In an oil-filled transformer, mineral oil (MO) is widely used as an insulating and cooling agent worldwide. Due to new environmental regulations, scientists have recommended highly environment-friendly insulating liquid for transformers. Polar contaminations in the oil always affect the dielectric and thermal performances of the oil negatively. Therefore, in this paper, the investigation is carried out on the effect of relative moisture content on the dielectric strength and partial discharge behavior of the oil. Moisture in the ester oil is an allied component that is very hazardous and can cause an inevitable degradation with its contamination of the paper-oil insulation in the transformers. To investigate the effect of moisture on dielectric degradation, two natural esters namely FR3 and palm fatty acid ester (PFAE) oils are used for the study. Partial discharge inception voltage (PDIV) is studied using a needle plane electrode to evaluate the effect of moisture on the oil. The study is performed at different temperatures and moisture levels for each oil. The relative saturation moisture content at a particular temperature is investigated for both the ester oils. It is observed that with the rise in temperature, the viscosity of the oil decreases, and relative moisture content increases. As the viscosity decreases oil molecules' movements ease with heat making the oil molecular randomness, and PDIV decreases. From the experimental investigation, the effect of moisture on PDIV and its relationship is analysed.