Fault current tests of a 5-m HTS cable

The first industrial demonstration of a three-phase, HTS power transmission cable at the Southwire manufacturing complex is in progress. One crucial issue during operation of the 30-m HTS cables is whether they can survive the fault current (which can be over an order of magnitude higher than the operating current) in the event of a short circuit fault and how HTS cables and the cryogenic system would respond. Simulated fault-current tests were performed at ORNL on a 5-m cable. This single-phase cable was constructed in the same way as the 30-m cables and is also rated for 1250 A at 7.2 kV AC line-to-ground voltage. Tests were performed with fault-current pulses of up to 15 kA (for 0.5 s) with pulse lengths of up to 5 s (at 6.8 kA). Although a large voltage drop was produced across the HTS cable during the fault-current pulse, no significant changes in the coolant temperature, pressure, or joint resistance were observed. The cable survived all 15 simulated fault-current shots without any degradation in its V-I characteristics.