Modeling and Measurements of Electric Fields in Composite Oil/Cellulose Insulation

In this paper we report on basic studies of the electric fields under DC stress in a composite insulation consisting of transformer oil and oil-impregnated pressboard, typical for HVDC converter transformers. The time dependent electrical fields in our model geometry are measured using electro-optic Kerr method, and theoretically studied with an ion drift-diffusion conduction model. The measured and calculated electrical fields are compared and analyzed.