Experimental investigations on different insulating liquids and mixtures for power transformers

This paper presents a comparison between mineral, ester and silicone oils, and mixtures with mineral oil based on their mean properties, namely the heat transfer, the dielectric strength, the aging stability and the electrostatic charging tendency (ECT), in order to select the most appropriate one for power transformers. The heat transfer is studied by means of kinematic viscosity. The measurements of breakdown voltage are achieved according to IEC 60156 specifications and analyzed by Gaussian's statistics method. The results of aging tests in temperature and in contact with atmosphere as well as the ECT versus the oil humidity and resistivity are also presented.