A novel measurement-protection-integrated current transformer based on hybrid core and magnetic field sensor

Current transformers (CTs) are widely used for energy metering, relay protection, condition monitoring and control circuits. However, CT saturation may lead to non-negligible measurement errors and relay malfunctions, posing a threat to the stability and security of the power grid. In order to address the problem of CT saturation, a novel measurement-protection-integrated current transformer (MPICT) is proposed. First, the working states of the MPICT are summarised and the approximate expressions for the steady-state measuring characteristics, the transient response characteristics, and the measurement errors are derived from the equivalent circuit model. Then, the feasibility of the MPICT and the theoretical analyses are verified by the 3D FEM simulation imitating the presented MPICT excited by diverse currents. Finally, a down-scale prototype is fabricated and a series of tests are conducted in the laboratory to validate the effectiveness of the equipment. The simulation and experimental results suggest that the output of the MPICT can accurately reconstruct the primary current waveform, even if the primary current contains decaying or constant DC component. In order to address the problem of CT saturation, a novel measurement-protection-integrated current transformer (MPICT) is proposed. To verify the feasibility and effectiveness of the MPICT, a series of theoretical analyses, 3D FEM simulations and laboratory tests are conducted. The simulation and experimental results indicate that the MPICT not only simultaneously satisfies the accuracy requirements in IEC 61,869-2 for measuring CTs and protective CTs, but also has excellent DC tolerance capability. image