6.6 kV resistive superconducting fault current limiter based on YBCO films

We present the fabrication and short circuit tests of a three-phase 6.6 kV resistive superconducting fault current limiter (SFCL) demonstrator based on YBCO films. The SFCL is operated at three-phase 6.6 kV_rms and has the quench development current of 200 Arms in the liquid nitrogen temperature. Individual components were YBCO films of 300 nm thickness covered by 140 nm thick Au on the sapphire substrates of 4´´ diameter. The films were patterned into bi-spiral lines of width 5 mm. The wafers have the operating voltage 600 V_rms and the critical current 47 A in average. Eight wafers were connected in series to make a unit of rated voltage 4.8 kV_rms, and six units were connected in parallel to complete a single phase SFCL. Equal shunt resistors across the wafers in series have been adopted to induce the simultaneous quenches of the components for equal voltage applications. Voltage enhancement of single unit is to handle asymmetric faults such as a line-to-line fault. Short circuit tests for line to ground, line to line and 3 phases fault showed that the SFCL is highly reliable for the current limiting capability. The SFCL successfully suppressed the fault current up to 10 kA below 900 A. Particularly, the current limitation was found to be independent of the maximum fault current. Detailed study on the fabrication and short circuit tests will be presented.