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.