Evaluation and comparing the loss of life for outdoor and MV/LV prefabricated oil immersed power transformer based on nonlinear thermal models

Power transformers are the most critical and expensive equipment in the field of transmission and distribution of electric energy. Any major fault in these units can cause not only catastrophic damage to various equipments but also cause interruption of electricity supply. These direct or indirect effects often lead to large economic losses. The most important parameter in transformers life expectancy is the insulation hot-spot temperature value which accelerates the rate of aging of the insulation. This Study proposes a life expectancy model for oil immersed power transformer using the hot-spot temperature based on transformer nonlinear hot-spot and top-oil temperature rise models. Since the thermal transfer is different for indoor and outdoor transformers considering their operating conditions, their thermal and loss of life models are different and are analyzed and compared in this study.