Análise de métodos de estimativas de perdas por indução de Corrente de Foucault com consideração da temperatura por análise fluidodinâmica em enrolamentos de transformadores de potência

Abstract

Temperature rise in transformers is caused by heat dissipation due to internal losses. The main sources of heat in power transformers in steady-state are those generated when under full load being mainly caused by the applied current and those originated by the magnetic field. Consideration of the magnetic field in the loss estimation is necessary because it can reach high values depending on the design and make the internal temperature calculation inaccurate. To reduce the inaccuracy in the results, in this work the losses are calculated using the Finite Element Method (FEM) considering the conductor temperature by coupling with fluid dynamic analysis. 2D and 3D approximations with single and sectioned cables were used to make comparisons with the calculation modes, analyzing the influence of the temperature effect on the additional losses created by Eddy current and compared with the analytical form presented in the specialized literature. The results show that the analytical calculations present a good initial estimate of additional Eddy current losses, being more conservative than those obtained by computer simulation and indicating in advance the projects that should be applied for mitigation strategies. However, the models considered in this research disregard radial magnetic fields, being a source of uncertainty that can cause unforeseen hot spots depending on the project. In addition, the results obtained by the 3D models had lower values in relation to those obtained by the 2D case and the analytical one, identifying correction factors for both cases. The consideration of the electromagnetic coupling with the dynamic analysis of fluids indicated that the temperature rise causes a decrease in Eddy current losses, being identified the sensitivity that measures the influence of temperature in the calculation.