A relative comparison method of thermal deterioration of pole-mounted transformers is developed. In the developedmethod, smart-meter data is employed to calculate load currents passing through pole-mounted transformers, and theirthermal deterioration is evaluated relatively. The developed method is applied to some pole-mounted transformers,and clear differences are found in the thermal deterioration index of insulating paper and gaskets. The developedmethod will help in determining the priority of the replacement in consideration of the thermal deterioration.
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