2-D coupled fluid-thermal analysis of oil-immersed power transformers based on finite element method

The thermal dynamics of transformer is a critical issue during operation, since it limits the lifespan and the load capacity of transformers. This paper introduces a finite element method (FEM) coupled fluid-thermal to investigate the thermal performance of oil-immersed power transformers. A two-dimensional (2-D) axially symmetric model is established, according to the basic parameters of a 250 kVA/10kV oil-immersed transformer under rated load. The model, which is established by COMSOL Multiphysics, calculates the oil flow velocity, hot-spot temperature and average temperature rise of different parts in the transformer, and the location of hot-spot and the characteristic of temperature distribution was found out. In order to guarantee the accuracy of simulation, discs, insulation cylinders, and the effects of temperature on oil parameters are considered. Moreover, the influence of thermal performance by using barriers and radiators are investigated. The results indicate the specific effect of improving thermal performance by using barriers or radiators. In the end of the paper, the possibility of using the proposed model to optimize cooling-system configuration, and the applicability to set parameters of non-electricity protection are discussed.