Numerical Analysis of Internal and External Radiation Heat Transfer in Oil-immersed Transformer

Abstract

Hot spot temperature is an important index to measure the insulation performance and safety margin of oil-immersed transformer, and it is of great significance to calculate it quickly and accurately. In this paper, the internal and external radiation heat transfer mechanism of oil-immersed transformer is studied. A numerical calculation model of radiation heat transfer is set up based on the radiation transfer equation (RTE) and Stephen-Boltzmann Equation. A set of 110 kV oil-immersed transformer is taken as an example, the numerical analysis of its internal and external radiation heat transfer process is performed through finite element simulation. The results show that the temperature error of the winding hot spot caused by ignoring the internal radiation process is less than 2%, and the calculation efficiency can be improved by 33%. The external radiation heat transfer coefficient is in the same order of magnitude as the convective heat transfer coefficient. The effect of external radiation heat transfer on the hot spot temperature of the winding reaches up to 16%, which cannot be ignored in the numerical calculation.