Fault current limiters and fault current switches based on wide HTS tapes: low cryo-consumption, new applications

When the fault current limiter yields influential response within 0.1 milliseconds, it demonstrates ultra-fast switching behaviour that is significantly faster than the response of the best mechanical and superconducting devices. Such ultra-fast response was demonstrated in recently developed superconducting fault current limiters (SFCLs) of inductive type. Secondary coil of the limiter was constructed from a set of closed rings made out of 40 mm wide YBCO coated conductor that was capable of nucleating wide normal zone in the beginning of quench process. Due to reduction of heat capacity and avoiding internal and external shunts, the ultra-fast switching behaviour with characteristic times of 50-100 microseconds was achieved. The ultra-fast performance results in a suppression of energy absorbed in the device during transient/quenching process as well as in low power dissipation after quenching of the superconducting element. This allows to maintain a very low power dissipation in the limiting modus duration which may be extended therefore to hours. Drastic reduction (by a factor of 10-50 in comparison with conventional types of SFCLs) of cryoconsumption was experimentally demonstrated at both normal operating modus and limiting (quenched) modus. Different ways for implementation of ultra-fast switching performance in fault current limiters are considered and discussed.