Mechanism and numerical model of bubble effect in oil-paper insulation based on microtubule model

In this paper, a numerical model of bubble evolution is established by studying the microstructure of pressboard and the physical process of bubble generation. In the model, the porous structure of fibers is equivalent to microtubules, the gases in the bubbles are classified into two categories, and...

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Bibliographic Details
Published in:IEEE transactions on dielectrics and electrical insulation 2020-10, Vol.27 (5), p.1529-1537
Main Authors: Liu, Yunpeng, Chao, Nijie, Zhao, Tao, Tong, Yixin, Jia, Chenhao
Format: Article
Language:English
Subjects:
Aging
bubble effect
Bubbles
Equations of state
Evaporation rate
Evolution
Gases
Ideal gas
Insulation
Mathematical model
Mathematical models
mechanism
Moisture
Moisture content
numerical model
Numerical models
oil-paper insulation
Power transformers
transformer
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Summary:In this paper, a numerical model of bubble evolution is established by studying the microstructure of pressboard and the physical process of bubble generation. In the model, the porous structure of fibers is equivalent to microtubules, the gases in the bubbles are classified into two categories, and the ideal gas state equation is used to describe the bubble state. Then the pressure conditions at the bubble boundary and the evaporation rate of water are taken as solution conditions to solve the physical quantities in the state equation. The numerical model provides a new way to calculate the initial temperature of bubble escape (ITBE). And the bubble evolution inside the pressboard is obtained which is hard to be observed in experiment. After that, the influences of moisture content of pressboard and cellulose aging on ITBE in the numerical model are discussed. The model results show that the expansion rate of bubble is not uniform. Bubble growth is slow in the early stage of temperature rise, when the temperature reaches a certain threshold the growth rate of bubble radius increases significantly, which is of great significance to the temperature limit on oil-immersed power transformers.
ISSN:1070-9878
1558-4135
DOI:10.1109/TDEI.2020.008744