Document Type : Original Paper


       Temperature, especially the hot spot temperature and top oil temperature, have played the most effective factor on the insulation life of the transformer. The prediction of top oil temperature and hot spot temperature is very important for estimating the loss of life of the transformer in the system. Therefore, an accurate technique is needed for solving the thermal models. This study determines an accurate hot spot temperature and then evaluates the loss of life of transformer according to the numerical analysis method. An alternative solution for solving the thermal model is proposed in this work. Results are compared with the actual temperature, which were measured by fiber optic sensors. The proposed technique is implemented on 250 electrical power transformer