Testing of a 1.25-m HTS Cable Made from YBCO Tapes

Ultera and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested a 1.25-m-long, prototype high-temperature superconducting (HTS) power cable made from 1-cm-wide, second-generation YBa2Cu3Ox (YBCO)-coated conductor tapes. Electrical tests of this cable were performed in boiling liquid nitrogen at 77 K. DC testing of the 1.25-m cable included determination of the V-I curve, with a critical current of 4200 A. This was consistent with the properties of the 24 individual YBCO tapes. AC testing of the cable was conducted at currents up to 2500 Arms. The ac losses were measured calorimetrically by measuring the response of a calibrated temperature sensor placed on the former and electrically by use of a Rogowski coil with a lock-in amplifier. AC losses of about 2 W/m were measured at a cable ac current of 2000 Arms. Overcurrent testing was conducted at peak current values up to 12 kA for pulse lengths of 0.1-0.2 s. The cable temperature increased to 105 K for a 12 kA, 0.2 s overcurrent pulse, and the cable showed no degradation after the sequence of overcurrent testing. This commercial-grade HTS cable demonstrated the feasibility of second-generation YBCO tapes in an ac cable application.