HTS Cable System Shows Promise for Transforming Power Transmission and Distribution

By Consulting Specifying Engineer Staff September 25, 2006

A new second-generation high-temperature superconducting (HTS) cable system was unveiled this month in a $9 million project to deliver electric power to approximately 8,600 homes and businesses in suburban Columbus, Ohio.

The HTS cable is designed to reduce the cost of superconducting systems and bring the technology a step closer to commercial viability. The system was developed by a partnership of Carrollton, Ga.-based Southwire Company, American Electric Power, American Superconductor and the U.S. Dept. of Energy’s Oak Ridge National Laboratory.

Approximately 660 ft. of Triax HTS cable from Southwire is part of a system that distributes electric power to residential, commercial and industrial customers through AEP’s Bixby substation in Groveport, Ohio, in the installation phase of the two-year demonstration project.

Superconducting cables, operating at extremely low temperatures, eliminate virtually all resistance to the flow of electric current. Operators claim that one HTS cable can carry as much current as 18 large copper cables, with much less energy loss.

“This project demonstrates the potential role for superconductivity in modernizing our electricity system,” said U.S. Secretary of Energy Samuel W. Bodman. “This new development allows power lines to increase capacity in congested urban areas while using less space. I’m pleased to be part of this excellent and innovative team.”

Superconducting cables are seen as one solution to the challenge of providing electric power to densely populated areas. In an increasing number of cities, there is little room underground to bury cable. The cost of building new tunnels or ducts, including the cost of acquiring the rights-of-way, to lay additional cable is prohibitive—representing up to 75% of a cable project. With their higher capacity, superconducting cables have the potential to multiply the supply of electricity to an area using the existing infrastructure footprint.

Despite these advantages, high-temperature superconducting cable systems are still expensive. The U.S. Department of Energy provided partial funding through its Superconductivity Partnership with Industry program to help make the Columbus project possible.

“AEP has a long history of supporting innovation in power generation, transmission and distribution. The demonstration of the Triax cable at our Bixby Station is another example of how we seek to advance technologies to help increase the capacity and ensure the reliability of our power delivery network,” said Michael G. Morris, AEP’s chairman, president and chief executive officer. “Over the next two years, this project will provide an invaluable, real-world test of state-of-the-art superconducting cable technology on an operating power distribution system.”

Designed in a joint venture of Southwire and nkt cables, a European cable manufacturer, this second-generation cable design can carry up to 3,000 amps of power, approximately three times more current than other superconducting projects now energized or under construction.

The Triax cable places the three necessary phase conductors concentrically around a common central core, surrounded by a copper shield. Earlier designs required a separate cable for each phase. The compact Triax design reduces by half the quantity of HTS wire needed. It also reduces the cold surface area, and with it, the critical cooling requirements. Both of these innovations lower the cost of HTS systems.

For more information on the new HTS cable design and the Bixby substation demonstration project, go to .