Power Cables That Squeeze More Juice Into Less Space

Forget New York. The really pricey real estate is underground, where power cables are stored. These wires are the foundation of America's overloaded and overpacked power-distribution system. Upgrading them without expanding the cable trenches at huge additional cost will be a daunting challenge.

Now, after years of development, researchers say high-temperature superconducting (HTS) wires could be the solution. Because they carry electricity with no resistance, a single, thin strand of HTS wire can carry the same power load as a thick copper bundle. American Superconductor Corp., based in Westborough, Mass., and Pirelli Cables & Systems of Italy recently finished spooling 30 km of HTS supercable to be installed underground at Detroit Edison's 60-year-old Frisbie distribution station next spring. This will be the first use of HTS cable in a commercial utility grid.

Until recently, superconducting wires were impractical because they had to be cooled to near absolute zero; only high-cost liquid helium could do the job. HTS cables operate at warmer temperatures and so can be cooled in relatively cheap liquid nitrogen. Where space is at a premium, this makes them an attractive alternative to conventional copper wire. At Frisbie, nine copper cables, carrying 100 million watts of power, will be replaced with three superconducting cables capable of handling the same load.

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