Abstract
In order to study the characteristics of the temperature variation in oil-immersed power transformer windings during operation, a two-dimensional transient fluid-thermal coupling calculation method for the transient temperature rising of transformer windings is proposed. Based on the dimensionless least-square finite element method (DLSFEM), the two-dimensional transient fluid-thermal coupling calculation method calculates the velocity distribution of the transformer flow field at different time instants, and based on the upwind finite element method, the temperature distribution at each moment is calculated. Considering the influence of the nonlinear material properties and winding Joule loss on the calculation results, the sequential iteration method is applied to solve the fluid-thermal coupling problem, and finally, the characteristics of the field temperature change are obtained. Compared with the traditional least-square finite element method, the DLSFEM has smaller stiffness matrix number conditions, and the corresponding discrete equations have better convergence. An oil-immersed power transformer winding model is taken as an instance, and the temperature distribution is calculated by the proposed method and the commercial computational fluid dynamic software Fluent. The calculation results of the proposed method are basically consistent with those of Fluent, and its iterative number is much less than that of Fluent, which greatly improves the calculation efficiency.
Highlights
The oil-immersed power transformer is one of the main equipment in the power system, whose safe and stable operation is essential to the power system
The calculation of the temperature rising of the oil-immersed power transformer windings is a heat transfer problem of fluid–solid coupling
The results show that the leastsquare finite element method (LSFEM) has better convergence and accuracy than the finite volume method (FVM), and it has found a wider range of application in the computational fluid dynamic field
Summary
The oil-immersed power transformer is one of the main equipment in the power system, whose safe and stable operation is essential to the power system. The calculation of the temperature rising of the oil-immersed power transformer windings is a heat transfer problem of fluid–solid coupling.. The partition method needs to establish the heat transfer computational models of the fluid and the solid region separately, and the coupling interface conditions between the fluid and the solid are satisfied by the sequential iteration. The FEM is an efficient numerical calculation method that can solve various computational fluid dynamic problems, and the continuity of heat flow density can be satisfied automatically and does not need to be treated separately as the FVM does. It has good adaptability when dealing with complex boundaries.
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