Charge behavior and field measurement techniques in different kinds of insulating oil for power transformers

From viewpoints of low environment impact, some kinds of environment-friendly insulating oils for power transformers have been developed. This paper deals with the discussion of charge behavior in these new oils by an electro-optic field measurement. Several potent insulating oils for power transformers have been proposed because of some excellent features not only on electrical but also chemical and economical points of view. In addition, the charge behavior in the insulating oils should be clarified for the insulation design of power transformers, because the space charge in oils strongly influences the transient and steady state electric field in high voltage apparatus. We compare the electric field characteristics in the insulating oils each other, and discuss the space charge behavior.