ABSTRACT As a critical hub in energy transmission, the operating condition of the large power transformer directly determines the safety and stability of the modern power system. Dielectric loss (tan δ ) measurement is a fundamental and widely adopted technique for assessing transformer insulation conditions. However, conventional dielectric loss testing primarily reflects the overall insulation state of the transformer, making it difficult to accurately identify and localize insulation defects within specific components. To address this challenge, this study proposes a novel part dielectric loss assessment method. By separately measuring the dielectric loss factors of different structural components and explicitly accounting for transformer configuration and inter‐component coupling effects, refined diagnostic parameters are established for localized insulation evaluation. The proposed method effectively suppresses the capacitance‐induced averaging effect inherent in conventional measurements and enables independent assessment of individual insulation paths. Finally, experimental results demonstrate that the proposed approach can accurately identify the location of insulation defects under low‐voltage test conditions, while maintaining high robustness against measurement interference. The proposed method provides a practical and scalable solution for precise insulation diagnosis in large power transformers, offering significant potential benefits for improving fault localization accuracy, reducing maintenance uncertainty, and enhancing the long‐term reliability of power equipment.
Zhan et al. (Thu,) studied this question.