With the continuous rise in the load demand at consumer end, the performance of the existing operating electrical machines gets affected. The increasing temperature of earth's surface due to solar radiation is another reason of the rise in the temperature of the electrical machines. Power transformers are one of the electrical machines whose performance is directly affected by its inner and outer temperature values as they are generally installed outdoors. The life of the power transformer

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... es gradually with the time and sometimes the severe outdoors surface temperatures may lead to sudden explosions that also obstruct the operation of the other associated machines as well. Therefore, thermal modeling of outdoor power transformers should include the consideration of variation in environmental temperature. This is expected to create an opportunity for the research in this field. This includes developing computational thermal models simulation using appropriate software tools. These models can be employed to evaluate the actual operational age of power transformers by estimating equivalent life at the reference temperature on the basis of the time period of the estimated temperature cycle causing acceleration of aging. This paper presents a MATLAB/ Simulink based thermal model determining temperature in increasing the aging acceleration factor, which has been used for estimation of the loss of life of the transformer. Further, the effect of outdoors surface temperature due to the influence of solar radiation for increasing the loss of life of power transformer has also been studied and verified by using the thermal model. The proposed model has been validated using real time data gathered from the power transformer in operation at 220kV GSS, Jhalamand, Jodhpur.