Thermal Experimental Evaluation of a Power Transformer Under OD/OF/ON Cooling Conditions

Power transformers are extremely important for electrical systems and its internal temperatures rule the equipment lifespan. To keep the operation under safe conditions, with temperatures below the limits from standards, a cooling system must be designed to ensure the correct heat transfer to the external environment. The internal circulation of cooling system can be by natural-oil, forced-oil or directed-oil, each one with its characteristics. This study presents an experimental comparison of the thermal performance of a prototype transformer operating with the three cooling modes. A set of 22 optical fiber sensors along the HV windings, top oil and radiator inlet, and a thermal camera make possible to observe the temperature distribution along the transformer and to identify the effects of each cooling mode, providing valuable information for thermal design of more reliable transformers.