Saturated iron-core superconducting fault current limiter is a kind of promising device for short-circuit current limiting. During normal operation, large ampere-turns created with DC in the secondary superconducting HTS coil drive the core into saturation. This lowers impedance of the copper coil in the primary AC side near to that of an air - core coil. During a fault, a large fault current demagnetizes the core and drives it from the saturated to unsaturated state (linear B - H region). This increases the primary AC coil impedance. The increased impedance limits the fault current to the desired level. The HTS DC bias coil with Bi2223 and YBCO is developed. Since strongly anisotropic Bi-2223 exhibits an enormous suppression of irreversibility field to the very low value of ~0.2 T at 77K, the second-generation YBCO is used to optimize the magnetic field distribution. The HTS DC coil is composed of 80 Bi-2223 double pancake coils and 8 YBCO double pancake coils, and the rated ampere-turns are 468000 at 72K. The used Bi-2223 tape is produced by Sumitomo, and the critical current is 220A (77K, self-field). The used YBCO tape is produced by Shanghai Superconductor, and the critical current is 100A (77K, self-field). Both of the Bi-2223 and YBCO double pancake coils are fabricated, and the critical current is more than 175A (77K, self-field) for each double pancake coil, which are essentially in agreement with the simulation results.
|Submitters Country||P.R. China|