CURRENT-LIMITING PERFORMANCE OF A YBA2CU3O7-X SUPERCONDUCTOR BY THE TRANSITION FROM SUPERCONDUCTING TO NORMAL-CONDUCTING STATE

Current-limiting performance of a YBCO superconducting element in a lo w-voltage circuit is described. The element produces the resistance as soon as the instantaneous value of an AC overcurrent passing through the element exceeds the critical current. The resistance does not appe ar in part but in all parts throughout the length of the element. Howe ver the resistance of the single element in normal-conducting state is too low to limit the overcurrent ent. Therefore, the model fault-curr ent limiter (FCL) is constructed by connecting 28 pieces of supercondu cting elements in series. The FCL produces total resistance of 4.5 Ome ga at 12 A. The FCL actually limits the peak value of the scaled-down short-circuit current from 23.0A to 12.8A in an AC 100 V circuit. For an actual FCL in power distribution systems, a huge total number of 9. 9 . 10(5) elements are necessary to be assembled. This number is expec ted to be reduced by an improvement of the electrical characteristics of the YBCO superconducting element.