Error Analysis of Current Transformer with Combined Magnetic Core under the Influence of DC Component

The increasing DC current component in the power supply system will have a great impact on the measurement accuracy of traditional current transformers. Since the hysteresis loop of the magnetic core material is nonlinear, the secondary current will be distorted when the measured current contains a DC component. In this paper, the distortion characteristics of the secondary current under different magnitudes of DC component and AC current are studied, and the hysteresis loop of the magnetic core material is considered. Then, the core structure of the transformer, which can accurately measure the current with the DC component, is studied. Specifically, high permeability permalloy and high saturation magnetic induction cold rolled silicon steel are combined radially, axially, and circumferentially. The analysis found that when the two types of materials are radially combined, and the inner layer is permalloy and the outer layer is cold-rolled silicon steel, the measurement accuracy is higher. The current transformer with combined magnetic core can not only reduce the measurement error of low excitation and no DC component, but also solve the problem of core saturation caused by DC component.