Charge behavior in Palm Fatty Acid Ester Oil (PFAE) / Pressboard composite insulation system with charged oil flow

Palm Fatty Acid Ester Oil (PFAE) is expected as one of the substitutes for mineral oil of transformers owing to not only the high biodegradation but also the good insulation performance. In this paper, the electric field strength and its time transition in PFAE / Pressboard composite insulation system??under charged oil flow were directly measured by using Kerr electro-optic technique. We found that the electric field was generated by space charges in PFAE and was temporally changed with charge behavior. By comparison with high charging mineral oil, we clarified that the feature of the charge behavior in PFAE was similar to that in the mineral oil, but the behavior of electric field was different due to the variation of electric properties such as permittivity, relaxing time and charge density.