Simulation Analysis about Anti-DC Effect of Current Transformer with Air Gapped Core

Current transformer (CT) is wildly used in the power system. The resistance of CT to DC bias is important for the operation of power system. According to the J-A theory, the hysteresis loop of closed and air gapped core was simulated, and the magnetic properties of air gapped cores with different gap length were studied. Based on the simulink tools, the magnetization curve of core was simplified. Furthermore the simulation model was built for the error investigation of the CT with air gapped core. The angle difference and ratio difference were calculated for the CT with closed and air gapped cores in condition of DC bias. The addition of air gap has little effect on the maximum magnetic density of core. But it reduced the slope of the linear part of the magnetization curve, and the core cannot be easily saturated. The air gapped core can improve the error of the CT under DC bias.