Performance analysis of transformer liquid insulation system under various environmental conditions

The proposed work aims to investigate the aging behavior of distribution transformer's (DT) liquid insulation system at various environmental conditions, by considering humidity as a frequently variable environmental factor. Most commonly used liquid insulation system in DT's is mineral oil (MO) as it is cheap, having good physical, dielectric and thermal properties. While varying the relative humidity of air artificially using humidity chamber from 20 % – 100 %, there is a notable increase in water content level of MO samples. After that, the samples are aged at 120°C upto 1000 hours at closed condition. Then critical electrical, chemical and physical characteristics are analyzed. It is found that, degradation rate of MO increases rapidly with increase in relative humidity.