Investigation on static electrification phenomenon of ester liquids and mineral oil

This paper aims at the comparison of the Electrostatic Charging Tendency (ECT) of mineral, vegetable and synthetic oils using a spinning disk system (CIGRE Cell) covered on its both sides with different types of pressboards and papers. The ECT of insulating oils generated by the charge concentration gradient at the oil - pressboard/paper interfaces are analyzed in function of the rotating speed of the disk. It is shown that the generated charge is slightly higher with vegetable oil than that with mineral and synthetic ester oils. This may be due to differences in the molecular structures of these oils, whose interaction with the pressboard/paper is different; the phenomena occurring at the double-layer (interface) are not identical. However, the differences observed do not constitute an obstacle to the use of vegetable oil as a substitute for mineral or synthetic oils, with respect to the problems and risks associated with static electrification phenomena.