Study on static electrification of palm fatty acid ester (PFAE) oil using mini static tester

Palm fatty acid ester (PFAE) oil is an alternative insulating liquid of power transformer that has good biodegradable properties. As a part of insulating system of power transformer, PFAE should also has a low risk in term of static electrification that may degrade electrical strength of solid insulation due to charge accumulation at its surface during oil circulating. Charge potential value could describe the possibility of insulating oil in involving on charge accumulation at the surface of solid insulation. This can be calculated from charge density through electrostatic charge tendency (ECT) and volume resistivity. This study using mini-static-tester to measure ECT since it is easy to reproduce the specimen and suitable for standardization. Since PFAE has higher polarity than mineral oil, PFAE has larger charges than mineral oil. Even though static charges are estimated to generate on the pressboard surface easily, generated charges are estimated to escape from pressboard surface because of its lower resistivity. Variation of charge density and volume resistivity of several types (i.e. PFAE and mineral) and conditions (i.e. with-additives, non-additives, unused, and aged) of oil will influence to its charge potential.