Coil Design of 200 MVA/200 kV DC Superconducting Fault Current Limiter by Employing Iron Yoke

With increase of direct current (dc) transmission voltage and capacity, the short-circuit fault current of dc transmission is one of the serious difficulties in a high-power dc system. In order to reduce the fault current, we propose a coil design method of a 200 MVA/200 kV resistive dc superconducting fault current limiter (DC-SFCL). The target is to limit the short-circuit current to less than 1-35% of the predicted value when the dc short-circuit occurs. However, the cost of DC-SFCL in high-power dc system is relatively high, which weakens the advantage of resistive DC-SFCL. For economic reasons, a pair of iron yokes is installed with the DC-SFCL limiting component, a superconductor coil, to alter the magnetic field and promote the utilization efficiency of YBCO coated conductors. We design two resistive DC-SFCLs without and with iron yokes for comparison for target limiting resistance 5 Ω. Influence of the iron yoke is investigated and discussed in two-dimensional finite element method models by simulation. The simulation result shows that the proposed method is effective and economical.