Kerr electro-optic measurement of electric field distribution in rapeseed ester oil and pressboard composite system

In oil-immersed power transformers, an insulating oil/pressboard (PB) composite insulation system is generally applied. In order to make power transformers more compact, it is necessary to optimize the insulation design with considering the charge behavior in liquid dielectrics. In addition, environment-friendly insulating oil for transformers is being interested. In this paper, we directly measured the electric field in parallel-plane electrodes and rapeseed ester oil/PB composite insulation system under dc voltage application using Kerr electro-optic technique. From the results, we compared the electric field in rapeseed ester oil with that in mineral oil and discussed the charge behavior in composite system. Finally, we confirmed the basic applicability of rapeseed ester oil for transformers.