Independent Effects of Aged Oil and Aged Paper on Moisture Evaluation of Power Transformers

Estimating the moisture content of insulation paper is important in transformer condition evaluation, the results of which are affected by thermal aging. This study investigates the independent effects of aged oil and aged paper on moisture equilibrium charts to determine which of the two primarily...

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Bibliographic Details
Published in:Electric power components and systems 2016-03, Vol.44 (5), p.556-564
Main Authors: Liao, Ruijin, Lin, Yuandi, Zhang, Yiyi, Xia, Huanhuan
Format: Article
Language:English
Subjects:
acidity
Charts
condition assessment
degree of polymerization
Electrical engineering
Equilibrium
Insulation
Mathematical analysis
Migration
Moisture
moisture absorption capacity
Moisture content
moisture equilibrium curves
moisture estimation
oil-paper insulation
Polymerization
power transformer
relative moisture content
thermal aging
Transformers
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Summary:Estimating the moisture content of insulation paper is important in transformer condition evaluation, the results of which are affected by thermal aging. This study investigates the independent effects of aged oil and aged paper on moisture equilibrium charts to determine which of the two primarily causes the inaccuracy in moisture estimation of aged transformers. A thermal aging experiment was conducted. At five aging degrees, four kinds of oil-paper insulation systems were formed: new oil-new paper, aged oil-new paper, new oil-aged paper, and aged oil-aged paper. Moisture equilibrium curves were drawn for each insulation system. The relative moisture content of oil and that of paper were calculated. Results showed that the moisture content of insulation paper decreased with aging, which led to the migration of the moisture equilibrium curves and further influenced the moisture estimation results. A comparative analysis showed that the migration of the moisture equilibrium curves was mainly caused by aged paper at the early and middle aging stages and by the synergistic effects of aged paper and aged oil at the late aging stage. The effects of aging on moisture distribution were verified using a retired transformer.
ISSN:1532-5008
1532-5016
DOI:10.1080/15325008.2015.1122104