Hot-spot aging state assessment of transformer oil-paper insulation based on the distribution of relaxation time

Transformers are critical components in power systems, energy storage systems, and electric vehicle charging infrastructure, making the assessment of their insulation condition highly important. To address the challenge of accurately evaluating the aging state of transformer hot-spot insulation paper, this paper proposes an oil–paper insulation aging assessment method based on the distribution of relaxation times (DRT). In this study, nonuniform oil–paper insulation samples with different aging degrees were prepared and tested. The DRT of each sample was obtained using the Regularized Non-Negative Least Squares (RNNLS) method, and the influence of aging on DRT characteristics was analyzed. Characteristic parameters representing the hot-spot aging condition were extracted, and a quantitative relationship model between these parameters, test temperature, and aging degree was established. The proposed approach provides a potential tool for precise evaluation of insulation aging, enabling more accurate information extraction and improved assessment of transformer hot-spot insulation conditions.