Influence of oil property on the space charge characteristics and electric field distortion in oil-paper insulation

The formation of space charge in oil/paper insulation system can lead to material degradation in the high electric field region and affect system reliability. It is important to understand factors that affect space charge formation in oil/paper insulation system. All the researches on the space charge characteristics of oil-paper insulation are all based on the oil impregnated insulation paper. In this paper, the space charge dynamic behavior of the oil impregnated insulation pressboard and the mixed insulation with a combination of oil gap and oil impregnated insulation pressboard were both studied. The oil property effect on the charge and electric field distribution behavior were discussed. The injected charge in aged oil impregnated insulation pressboard has a higher migration rate than that in new oil impregnated insulation pressboard. Compared with the oil impregnated insulation pressboard, a lot of space charges accumulate at the interface between oil and pressboard, which leads to obvious electric field distortion in oil gap and in oil impregnated insulation pressboard. The charge injected in new oil-paper insulation is more difficult to dissipation than that in aged oil-paper insulation.