Modelagem e análise da migração da umidade em sistema isolante papel-óleo de transformadores de potência
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2020-11-20
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Universidade Federal de Goiás
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This thesis aims to present an innovative tool designed to study how the phenomenon of moisture migration occurs inside insulating paper-oil systems of power transformers. The tool consists of a two-dimensional mathematical model, representing the dynamics of humidity in the oil-paper set and including the variations in electrical charging, which was developed using mathematical tools, existing studies, and the experience of specialists/analysts. Furthermore, this study includes a classification method developed to investigate some of the harmful effects of moisture in power transformers, considering the possibility of bubbles and free water formation. The novelty of this numerical method consists of a calculation methodology that contemplates the use of the finite element method - in two dimensions - applied to the concepts of mass transfer and thermal modeling of the transformer loading, considering the temperature differences between two windings. Additionally, the classification method includes the creation of: a) a categorization system for the coupling of a transformer and electric charging in five levels, from “A” to “E”, with the respective recommended actions; and b) an analysis that involves varying the different levels of loading applied to the equipment. The contribution of this work is an efficient method, implemented via a computational algorithm, which provides support for the maintenance team's decision making when unfavorable phenomena and conditions occur that can critically affect the useful life of the equipment, especially its insulation. This thesis presents some case studies of transformers in operation, under real load conditions, in which the data validation is performed through the comparation of obtained data with experimental collection and analysis of oil samples and the results of monitoring device. Therefore, this work is useful in supporting the classification and diagnosis of power transformers, through the prediction of humidity levels in the oil-paper isolating system, assisting on failure prevention in this equipment and capital loss to the owners of the transformers and consumers supplied by these.
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SOUSA, F. R. C. Modelagem e análise da migração da umidade em sistema isolante papel-óleo de transformadores de potência. 2020. 253 f. Tese (Doutorado em Engenharia Elétrica e da Computação) - Universidade Federal de Goiás, Goiânia, 2020.