Analysis of the Effect of Materials and Structural Parameters of Current Transformers on Their Excitation Current and Errors

This paper introduces the equivalent circuit of the current transformer (CT) represented by “Γ” type. Then, the relationship between the inductance, resistance, and excitation current in the excitation branch of the CT's equivalent circuit is explained according to the definition of excitation current provided in the standard GB 28040.2 (IEC 61869-2). Furthermore, the factors that influence the CT's excitation current and error, which include the magnetic permeability, losses, structural dimensions of the magnetic core, and resistance of the secondary circuit, are analyzed. This analysis serves as a theoretical basis for predicting changes in errors resulting from adjustments in material characteristics during the CT's long-term operation. Additionally, it can be utilized as a theoretical basis for the CT's design and performance improvement.