Application of resistive type SFCL to protect Bi-2223/Ag tape against AC over-currents

Based on the electrical behavior of Bi-2223/Ag tape in transient state, the possibility of SFCL application was investigated as a fundamental study for the protection of HTS power apparatus. For the experiments, the Bi-2223/Ag tape having the critical current of 56 A and the resistive type SFCL fabricated using three elements of YBCO thin films were examined. When the applied current exceeds the rated current of the SFCL, the current was limited to sufficiently low level, however, higher than 40 Vrms was not allowed considering power density of SFCL. On the other hand, as a method to increase the power density, a shunt resister across the SFCL was adopted to increase the allowed power density. In this case, the results showed that the over current was limited below the safe range for HTS tape and the SFCL was safe, although 100 V-rms was applied to the circuit. In conclusion, the switching power capacity of a SFCL could be increased by using a shunt resistor, and HTS tape could be protected safely within the quench margin.