Two-step Broadband Equivalent Circuit Modeling Method for Power Transformer Winding Based on Frequency Response Analysis and Bayesian Optimization

Frequency response analysis (FRA) is a well-established technique to detect transformer winding deformation faults. Its diagnostic application is based on the principle that a transformer winding can be represented by an equivalent circuit consisting of resistors, inductors, and capacitors. However, rapidly obtaining an accurate and physically meaningful broadband equivalent circuit model for windings remains challenging, limiting both the understanding of fault mechanisms and the generation of data for data-driven fault diagnosis methods. To address these difficulties, this study proposes a two-step broadband equivalent circuit modeling method for the transformer winding based on FRA and Bayesian optimization (BO), considering long-distance mutual inductances and capacitances. The proposed method is validated in a specially designed 10 kV power transformer. Subsequently, two kinds of winding deformation faults, including inter-disk short circuits (IDSCs) and disk space variations (DSVs), are simulated on the basis of the built model and compared with the experimental FRA data. The validation results confirm the accuracy and effectiveness of the proposed method in the construction of the equivalent winding circuit.