A Dynamic Top Oil Temperature Model of Power Transformers with consideration of the Tap Changer Position

In this paper, an optimized physical model for calculation of top oil temperature in power transformers is presented. The main contribution of this paper is to consider and to employ the heat transfer phenomenon inside transformer from bottom winding to top winding and from cooler inlet to cooler outlet of transformer with consideration of number of operating fans and pumps as well as the position of the tap changer. To validate the model, the empirical factors are estimated based on measurements of one month during the normal operation of the transformer and the model is tested and validated with measurements of other months during the normal operation of the transformer. It is worthwhile to note that the inputs of the model are ambient temperature, load and number of operating fans and…