Southwire Company and NKT Cables have formed a joint company to continue development and eventual commercialisation of HTS cable systems. Named ULTERA(TM), the new company will design and produce a 300-metre cable that will be installed during late 2005 in an electricity distribution system operated by American Electric Power (AEP) in Columbus, Ohio. Southwire and NT Cables will split the cost of developing the cable with the US Department of Energy, which will fund half of the project.
The new design used by Southwire and NKT Cables combines a three-phase system, which before required three separate HTS lines, into one cable. While the design has changed, the basic operation of the cable remains much the same. A hollow pipe forms the core. A layer of superconducting materials is wrapped around that tube, followed by a layer of electrical insulation. A second layer of HTS tape is added, acting as the second phase conductor. Another layer of insulation is added and the process is repeated. The final cable is wrapped in a copper shield and fed into a doubled-walled stainless steel tube. Liquid nitrogen is pumped through the tube’s inner chamber to cool the cable to an optimal superconducting temperature, around –321 degrees F. A vacuum between the two layers of stainless steel provides thermal insulation for the cable.