Aging evaluation and moisture prediction of oil-immersed cellulose insulation in field transformer using frequency domai
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ORIGINAL RESEARCH
Aging evaluation and moisture prediction of oil-immersed cellulose insulation in field transformer using frequency domain spectroscopy and aging kinetics model Jiefeng Liu . Xianhao Fan . Yiyi Zhang
. Chaohai Zhang . Zixiao Wang
Received: 29 December 2019 / Accepted: 15 May 2020 Ó Springer Nature B.V. 2020
Abstract This work aims to propose an improved model for aging evaluation and moisture prediction of transformer cellulose insulation, which is based on the combination of the advantages of both frequency domain spectroscopy (FDS) and cellulose aging kinetics model. In the present work, the FDS was firstly employed to achieve the prediction of the inside moisture according to its moisture-sensitive property. Then, the predicted moisture is applied to construct the
improved aging kinetics model, so that the aging condition of the transformer cellulose insulation can be predicted as well. The presented lab tests, as well as the field tests, have demonstrated the accuracy and feasibility of the proposed model. In that respect, the present contributions attempt to present a novel idea for the aging evaluation and moisture prediction for transformer cellulose insulation.
J. Liu X. Fan Y. Zhang (&) C. Zhang Z. Wang School of Electrical Engineering, Guangxi University, Nanning, China e-mail: [email protected]
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Cellulose
Graphic abstract
Keywords Transformer Cellulose insulation Frequency domain spectroscopy (FDS) Aging kinetics model
Introduction Power transformers are serviced as the key equipment in the modern power grid. The inside oil-paper system, the main form of insulation system in the transformers, will gradually deteriorate during the long-term service due to the synergistic effects of various stresses, such as thermal fields and electric fields (Emsley 1994, 1997, 2000; Liu et al. 2019a, b, 2020a). It is a fact that the aging of insulating oil can be improved (recovered) by filtering or changing oil (Feng et al. 2019), while the degradation of solid (cellulose) insulation is exactly irreversible. It means that the service life of transformer mainly depends on the aging degree of its solid (cellulose) insulation materials (Feng et al. 2018; Yang et al. 2018, 2019). Therefore, the condition prediction of both aging
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degree and moisture content (mc%) of transformer cellulose insulation is of great interest to the scholars. Reviewing the existing researches, the approaches for predicting the aging condition of transformer cellulose insulation materials are constituted of direct methods and indirect methods. The direct method is mainly formed of the viscosity test (Bozzini 1968; Van Bolhuis et al. 2002), which can be utilized to obtain the corresponding degree of polymerization (DP) of cellulose insulation materials. However, due to the incidental destructiveness, such the approach is usually applied in the lab condition rather than the field testing. In contrast, the indirect approaches can be achieved by various
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