1. Key Laboratory of Engineering Dielectrics and Its Application Ministry of Education Harbin University of Science and Technology Harbin 150080 China; 2. State Key Laboratory Breeding Base of Dielectrics Engineering Harbin University of Science and Technology Harbin 150080 China; 3. Heilongjiang Electric Power Research Institute Harbin 150090 China
Abstract:Oil-paper insulation is the main insulation of oil-immersed transformer. To study the effects of different oil replacement cycles on the aging state of transformer oil-paper insulation, the XY equivalent models of transformers were prepared under laboratory conditions, and the accelerated aging tests were carried out under different oil replacement cycles. Meanwhile, the dielectric responses in frequency domain were tested at different aging days, as well as the moisture, acid value and polymerization degree of oil-paper insulation. According to the comparative experimental results, it is found that, the longer the oil replacement cycle, the more obvious the turning point in the curve, and the turning point of the curve moves to the high frequency with the increase of temperature. The longer the oil replacement cycle, the more obvious the decline of dielectric loss factor before and after oil replacement. With the increase of test temperature, the coincidence degree in the high frequency range before and after the oil replacement is greater. The activation energy of oil-immersed pressboard by translating the dielectric loss factor curve in different frequency ranges before and after oil replacement is basically the same. Consequently, this paper studies the influence of different oil replacement cycles on the aging of transformer oil-paper insulation. A method for calculating activation energy of insulating paper in oil paper insulation before and after oil replacement is proposed, which establishes the theoretical basis for the quantitative characterization of oil replacement cycle, aging temperature and oil-paper insulation life of transformer in the follow-up study.
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