Transfer Impedance Modeling Method for HFCT Considering Current-Carrying Conductor Eccentricity and Air Gap

To enhance the accuracy and reliability of partial discharge monitoring devices for power transformers, this paper focuses on the verification of the transfer impedance of high-frequency current transformer (HFCT), which is a core parameter for assessing their performance. This article examines the influence of air gaps on the performance of the HFCT. Based on the Biot-Savart law, this paper derives the analytical solution for the induced electromotive force of the HFCT under eccentric conditions of the current-carrying conductor. A finite element model of the HFCT and current-carrying conductor was established using the Ansys Maxwell module to perform coupled magnetic circuit simulations. The conductor eccentricity was introduced to investigate the impact of conductor position on the transfer impedance of the HFCT. The research results indicate that the presence of the air gap leads to magnetic field leakage and uneven distribution, increasing measurement errors. The transfer impedance error is only related to the ratio of the inner and outer radii of the coil and the size of the air gap. The smaller the air gap, the less its impact on the transfer impedance verification results. This study provides a theoretical basis for the optimization of transfer impedance verification for the HFCT.