Development of Mold Transformer Life Evaluation Technology

In this paper, the fault history and main stress factors of molded transformers were identified, the long-term life was confirmed through accelerated deterioration experiments and failure rate analysis of epoxy insulators, and diagnostic parameters were derived. Through accelerated degradation experiments (accelerated stress: voltage and temperature), it was confirmed that $\tan\delta$ is a major state parameter that can determine the age change of mold transformer insulation. To verify the derived condition diagnosis parameters at the product level, we measured the $\tan\delta$ of each part under various conditions for mold transformers, and operated and discarded them. From the $\tan\delta$ measurement results, we have derived a life formula for knowing the life and remaining life of each part of the mold transformer.