Abstract —The first industrial demonstration of a three- phase high-temperature superconducting transmission power cable at the Southwire manufacturing complex is in progress. One crucial issue during operation of the 30-m HTS cables is whether they could 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 15 simulated fault-current shots without any degradation in its V-I characteristics. Index Terms —Critical current, current limitation, fault current, high-temperature superconducting cable. I. INTRODUCTION OUTHWIRE Company is demonstrating the world’s first industrial application of high-temperature superconduct- ing (HTS) power cables with a 30-m, three-phase cable system at its Carrollton, Ga., plant [1]. Oak Ridge National Laboratory (ORNL) worked very closely with Southwire in developing this cable system. An HTS cable test facility [2] was built and was used to test two 5-m single-phase cables for their dc and ac characteristics and the high-voltage integrity of the cold-dielectric design [3]. Another crucial issue for the operation of the 30-m HTS cables is whether they could survive the fault current (which can be over an order of magnitude higher than the operating current) in the event of a short circuit and how HTS cables and the cryogenic system would respond. Fault-current simulation tests were performed on the second 5-m HTS cable at the ORNL 5-m test facility. A 25-kA, 12-V dc power supply was reconfigured for this test. Tests were performed with fault-current pulses up to 15 kA for 0.5 s and 6.8 kA for 5 s. The cable survived all the fault-current pulses. We report in this paper the responses of the cable and the coolant during and immediately after the pulses. II. CABLE RESPONSE TO SIMULATED FAULT - CURRENT PULSES The cable was cooled down to about 81 K with liquid nitrogen (no pumping on the sub-cooler bath) at a pressure of Manuscript received August 18, 2000. This work was performed under a cooperative agreement between Southwire and ORNL. The latter is sponsored by the Office of EE-RE, DOE under contract DE-AC05- 00OR22725 with UT-Battelle, LLC. J. W. Lue, G. C. Barber, J. A. Demko, M. J. Gouge, and J. P. Stovall are with the Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA. R. L. Hughey and U. K. Sinha are with the Southwire Company, Carrollton, GA 30119 USA. about 4.7 atm and a flow rate of about 0.19 L/s (3 gpm). Short current pulses much larger than the critical current, I c (about 910 A), of the cable were applied to the cable to simulate fault currents in case of an in-service short circuit. The voltages across the phase conductor and the joint, the current and voltage of the shield conductor, and the temperature and pressure of the coolant during the pulse and for a period after the pulse were monitored. Shots were made first with a 1-s pulse at increasingly higher current from 4.8 to 12.8 kA. The pulse length was then increased to 2 s, and again up to 12.8-kA current pulses were applied. The pulse length was shortened to 0.5 s and a current of 15.3 kA was applied. Finally, the pulse length was lengthened to 5 s and a current of 6.8 kA was applied. A. Cable and Joint Voltages Fig. 1 shows the current and voltage traces of the cable on a typical shot. A fault-current pulse of about 12.8 kA was programmed to apply to the cable for 2 s. As soon as the current reached 12.8 kA, a voltage (V-cable) of about 3.2 V was developed across the cable. This and the voltage drops along the terminations and external power supply cables had apparently exceeded the power supply limit (12 V) and caused the current to drop. By the end of the 2-s pulse, the current was lowered to about 6.9 kA. However, the cable voltage continued to rise to over 5 V, indicating heating in the conductor. On the other hand, the cable-to-connector joint voltage (V-joint) was lowered from about 0.3 to 0.17 V in the same proportion as the current drop. 0 2 4 6 8 10 12 14 -1 0 1 2 3 4 5 6 0 2 4 6 8 10 Current V-cable V-joint C u r r e n t ( k A ) V o l t a g e ( V ) Time (s) Fig. 1. Cable (phase conductor) and joint voltages in response to a 12.8-kA, 2-s fault-current pulse. Fault-Current Tests of a 5-m HTS Cable J. W. Lue, G. C. Barber, J. A. Demko, M. J. Gouge, J. P. Stovall, R. L. Hughey, and U. K. Sinha S