Background. The linearized magnetization characteristic is widely used for analyzing transient processes in current transformers. Its main parameter is the magnetizing branch inductance corresponding to deep core saturation. Currently, analytical expressions for its calculation based on the geometric dimensions of the magnetic core are known. However, their application is complicated by the absence of actual core parameters in technical documentation. Another method for determining the magnetizing branch inductance involves the use of the peak dynamic and average magnetization curves obtained for the secondary winding. It is known that the magnetization curves of modern current transformers are almost horizontal under high magnetizing excitation, which makes it difficult to determine the magnetizing branch inductance with an accuracy of tens of µH using test equipment employed at electric power facilities. Therefore, the development of a method for determining the magnetizing branch inductance in the equivalent circuit of a current transformer under core saturation, providing measurement capability in the µH range, is an urgent task.
Materials and methods. Methods for determining the peak dynamic and average magnetization curves of the current transformer secondary winding were used. The proposed method is based on mathematical modeling techniques for nonlinear electrical circuits. Analytical expressions for calculating the inductance of a toroidal winding were used to evaluate the obtained results.
Results. Processing of experimental data obtained during a physical experiment using a TOL-10 current transformer made it possible to determine the magnetizing branch inductance values according to classical and proposed methods. It was found that the calculated inductance values obtained using classical methods have a spread of up to 50 µH for each magnetization curve, whereas the proposed method provides a spread of no more than 2 µH.
Conclusions. The proposed method makes it possible to measure the magnetizing branch inductance of a current transformer with an accuracy of several µH.