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The tri-axial HTS cable design uses three concentric superconducting layers for the phase conductors separated by a cold dielectric material. It offers an efficient HTS cable configuration by reducing the amount of superconductor needed, and placing all three phases in a single cryostat. Ultera and ORNL tested a 5-meter long tri-axial HTS cable and terminations designed to operate at 3 kA ac and 13.2 kV. Test results, including the thermal loads on the system, will be reported. An existing liquid nitrogen skid that circulates subcooled liquid nitrogen through the cable was initially designed for the heat loads on single phase cables at lower current ratings. The refrigeration needed for the 3 kA tri-axial cable configuration made it necessary to upgrade the nitrogen system to increase the cooling capacity. A description of the upgrades and performance of the system is provided. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The Southwire/ORNL team has conceived, designed, built, and tested a 5-m, three-phase, tri-axial cable with terminations. The cable has three concentric superconducting phases made of BSCCO-2223 HTS tapes, separated by layers of cold-dielectric tape with a copper braid as the grounding shield. The cable is enclosed in a flexible cryostat. Cooling of the cable and terminations is achieved by liquid nitrogen flowing through the annulus between the cable and the cryostat. A challenging analysis and design issue was development and implementation of an insulator material between the concentric phases with high enough thermal conductivity to meet temperature gradient requirements and acceptable mechanical and electrical performance. The resulting 3-phase, cold dielectric, cable and termination design is nearly as compact as the single-phase, co-axial design developed previously by Southwire/ORNL, and it represents the highest cable current density achievable in an electric ac power cable. This paper presents results from operation of the 1.3-kA root-mean-square (rms) phase current termination and design changes required to scale to 3-kA rms phase current. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Southwire Company is operating a high-temperature superconducting (HTS) cable system at its corporate headquarters. The 30-m long, 3-phase cable system is powering three Southwire manufacturing plants and is rated at 12.4-kV, 1250-A, 60-Hz. Cooling is provided by a pressurized liquid nitrogen system operating at 70-80 K. The cables were energized on January 5, 2000 for on-line testing and operation and in April 2000 were placed into extended service. As of June 1, 2001, the HTS cables have provided 100% of the customer load for 8000 hours. The cryogenic system has been in continuous operation since November 1999. The HTS cable system has not been the cause of any power outages to the average 20 MW industrial load served by the cable. The cable has been exposed to short-circuit currents caused by load-side faults without damage. Based upon field measurements described herein, the cable critical current — a key performance parameter — remains the same and has not been affected by the hours of real-world operation, further proving the viability of this promising technology. [ABSTRACT FROM AUTHOR]