1. State Grid Chongqing Electric Power Company Chongqing Electric Power Research Institute Chongqing 401123 China; 2. School of Electronics and Computer Science University of Southampton Southampton SO17 1BJ UK; 3. College of Engineering and Technology Xi’Nan University Chongqing 400037 China
Abstract：At present, most of the researches on space charge characteristics of oil-paper insulation are based on oil impregnated insulation paper. The pulse electro-acoustic system fails to test the space charge characteristics on the mixed insulation with the combination of oil gap and oil impregnated insulation paper. In this paper, the dynamic space charge behaviors of the mixed insulation with the combination of oil gap and oil impregnated insulation paper were studied, using the improved pulse electro-acoustic measurement system for the first time. The effect of space charge accumulation on internal electric field distribution of the mixed insulation system was analyzed. Results show that the conductivity of the oil or the oil impregnated insulation paper has great effects on the space charge and the electric field distortion at the interface and inner of the oil-paper insulation. The insulating oil degradation increases the oil-paper insulation system conductivity, which causes serious electric field distortion inside the oil-paper insulation. The largest electric field strength inside the oil impregnated insulation paper is about 2.5 times higher than the average electric field strength. The conductivity of the oil-paper insulation system increases as the oil impregnated paper conductivity increases, which reduces the electric field distortion inside the oil impregnated paper. But the rapid migration charge will result in significant heat effect that also easily induces breakdown. The following three aspects would be helpful to prevent the damage of space discharge, i.e., eliminating the space charge accumulation effects at the insulation structure interface, limiting the rapid migration of space charge inside the dielectrics or making the charge distributed more evenly within the dielectrics.
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2016, Vol. 31 
