The role of the type of insulating liquid in the transformer temperature distribution

The mineral oil is most frequently used liquid in insulation transformer system. However, increased interest in alternative insulating liquid for it, which includes synthetic ester and natural ester is observable for several years. However, for several years, the increased interest in insulating liquids as alternatives to mineral oil is observable, which include synthetic ester and natural ester. This is due to increasingly restrictive environmental legislation and fire safety. Mineral oil, in comparison with esters has a very good electric insulation properties and a lower viscosity. In turn the esters in comparison with oil, have a much greater biodegradability and have a much higher flash point, which suggests their favor. The influence of the type of insulating liquid on the efficiency of the cooling system of the transformer was presented in the paper. This efficiency was determined by designating the heat transfer coefficient α by liquids. This factor depends on the thermal properties of liquids, which includes the thermal conductivity λ, kinematic viscosity υ, specific heat cp, density ρ, and thermal expansion β. For the study mineral oil, synthetic ester and natural ester were used. The measurements of thermal properties were carried out in the temperature range from 25°C to 80°C