HTS wire consumption reduction in a coil with an actively controllable magnetic core for a fault current controller

For an effective fault current management in a smart grid, a fault current controller (FCC) has been proposed and actively developed. A previous attempt to reduce the superconducting wire consumption in a high-temperature superconducting coil for the FCC was to use a reversely magnetized core (RMC) using permanent magnets. Despite the previous study being effective to shorten the wire, there were some potential drawbacks: a demagnetization of the permanent magnets and uncontrollability. In the smart grid with renewable sources, a nominal line current can be time-varying, so a reverse bias point should not be fixed. Therefore, an actively controllable RMC is required. In this paper, an electromagnet was applied for a source of RMC. A reverse-bias point was actively adjusted by taking account of time-varying line current. This proposed bias method could reduce wire consumption. With optimal reverse bias current, the effective inductance was 4.3 times larger than that of the air core case. If we want to make the same inductance without RMC, wire consumption should be more than 2.07 times. This proposed method was so effective to apply to the distribution class FCC, which is our final target.