Frequency-Domain Dielectric Characteristic Parameter and Moisture Content Assessment Methods Study on Frequency-Domain Dielectric Spectroscopy of Oil-Paper Insulation for Transformers
1. State Key Laboratory of Power Transmission Equipment & System Security and New Technology Chongqing University Chongqing 400044 China 2. Chongqing Electric Power Corporation Electric Power Research Institute Yubei District Chongqing 401121 China 3. Electric power planning & engineering institute Beijing 100120 China 4. Yunnan Electric Power Research Institute (Group) Co., Ltd. Kunming 650051 China
Abstract：In order to better apply frequency-domain dielectric spectroscopy(FDS) in nondestruc- tive diagnosis of transformer insulation status, the experiment of oil-paper insulation sample in different moisture contents were tested by FDS at 30℃ and 60℃. On the basis of further study of the influence of moisture content and test temperature on frequency-domain dielectric property of oil-paper insulation, the loss factors tanδ corresponding to different test frequency points were proposed as characteristics to assess moisture content, and the quantitative relationships between the characteristics and moisture content were initially proposed. The temperature impact on FDS results could be eliminated by introducing the “frequency temperature shift factor”. It demonstrates that in the range of 10-1Hz to 102Hz, tanδ significantly increases with the increases of moisture content. The loss factors tanδ at 10-1Hz、100Hz、101Hz and 102Hz were utilized as characteristics to assess moisture content, and an exponential rule which could further be used for moisture content assessment was observed in the relation between the loss factors tanδ at different frequency points and moisture content. Using the master curve constructing by “frequency temperature shift factor” could eliminate the impact of test temperature on FDS results and improve accuracy of moisture content assessment.
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2013, Vol. 28 
