Calculation of Temperature Field of Oil-immersed Transformer under Varying Loss Loadings

Accurate prediction of the internal temperature is significant for assessing the operating status and remaining life of the oil-immersed transformer. In this study, a two-dimensional closed-loop simulation model of thermal-flow field for a 110-kV power transformer with the oil natural/air forced cooling mode is developed to predict the temperature distribution. The influence of eddy current loss, loss distribution and loss temperature effect on temperature distribution of transformer are compared and analyzed. The results showed that the ignorance of eddy loss makes the temperature of the high-voltage winding and the low-voltage winding decrease in the simulation, and the hot-spot temperature decreases by 3.44 °C. The loss distribution mainly affects the temperature at the top of high-voltage winding and the bottom of low-voltage winding, and the influence is insignificant. The temperature effect of loss is indispensable to be considered in the simulation as it is difficult to accurately estimate the reference temperature used in the calculation of loss. It is found that the loss loading mode has negligible effect on the location of the hot-spot temperature.