HTS fault current limiter concept

Fault current limiter (FCL) concepts based on non-inductive high temperature superconducting (HTS) coils were studied. The coils employed second generation (2G) HTS wire based on YBCO coated conductor currently under development at American superconductor corporation (AMSC) and other places. Two FCL concepts were studied: a) series and b) shunt. The series limiter employs a coil in series with the load and limits current by its increased resistance during the current limiting phase. This design is best for a single fault current limiting action, with resetting after the several minutes required cooling it down to its prefault temperature. The shunt limiter employs an inductor in parallel with the HTS coils. Once the HTS coil transitions to its normal state, fault current is limited by the impedance of the external inductor. An advantage of the shunt limiter is that with proper design, it could withstand multiple closely timed current limiting events. Since the 2G wire is becoming available in long lengths, now is the right time to initiate a commercial FCL product development program.