Power transformer thermal analysis by using an advanced coupled 3D heat transfer and fluid flow FEM model

Thermal performance in oil-immersed power transformers is governed by the flow of oil, acting both as an electrical insulator and a medium for the transfer of heat generated in the core and windings toward the tank and the surrounding air. This paper presents the development of an advanced three-dimensional (3D) finite element model for the coupled solution of heat transfer and fluid flow equations governing transformer thermal performance. The main advantages of the proposed method are: (i) no need to predefine the convection coefficients at the interfaces between the active part/tank walls and the circulating oil, (ii) detailed representation of specific transformer parts that play an important role in the accurate representation of oil flow and heat dissipation (such as winding cooling ducts and corrugated tank panels) through an automated design process, enhancing the model accuracy with the least possible computational effort and (iii) accurate definition of the transformer heat sources (core and windings loss). The proposed methodology provides an integrated tool for thermal simulation, able to predict detailed thermal distribution in a specific transformer, without requiring prior knowledge of nodal temperature or temperature gradient values. ►Advanced 3D FEM transformer model for the coupled solution of CFD-heat flow equations. ► Integrated tool for transformer thermal simulation. ►No need to predefine convection at the interfaces between the active part and oil. ►Automated design process, increased model accuracy and small computational effort. ►Predict thermal distribution without prior knowledge of thermal nodal properties.