Condition Evaluation for Aging State of Transformer Oil-paper Insulation Based on Time-frequency Domain Dielectric Characteristics

Author： Liu Jiefeng Liao Ruijin Zhang Yiyi Gong Chunyan Wang Cong Gao Jun

Publisher： Taylor & Francis Ltd

E-ISSN： 1532-5016|43|7|759-769

ISSN： 1532-5016

Source： Electric Power Components and Systems, Vol.43, Iss.7, 2015-04, pp. : 759-769

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Abstract

For the oil-impregnated power transformers in service, the condition of the main insulation system is very important. This article reports a non-destructive evaluation technique based on time-frequency domain dielectric characteristics. First, the polarization/depolarization current and frequency-domain spectroscopy were well measured under controlled laboratory conditions. Then, the recovery voltage curves and recovery voltage polarization spectroscopy were also obtained by using the conversion method between polarization/depolarization current and recovery voltage based on the extended Debye model. After that, the time-domain dielectric characteristics, which can represent oil-paper insulation aging, were extracted from the polarization/depolarization current curves, recovery voltage curves and recovery voltage polarization spectroscopy. In addition, the frequency-domain dielectric characteristics, which can represent the oil-paper insulation aging, were also proposed in terms of frequency domain spectroscopy. Finally, the change rules of time-frequency domain dielectric characteristics under different aging times were investigated in depth. Results show that the time-frequency domain dielectric characteristics are sensitive to the aging states of power transformers, which could be utilized to diagnose the aging state of oil-paper insulation in field power transformers.