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Electric Power Cables That Just Can't Resist

One by one, utilities around the world are testing a new generation of technologies that could revolutionize the way electricity is delivered to homes, schools, and factories.

Based on unique materials discovered 12 years ago, these technologies are built around wires and cables made from superconductors, which, under the right conditions, allow electric current to flow through them virtually without resistance.

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Already finding uses in small-scale electronic devices, these newest superconducting materials are poised to break into large-scale applications with savings - and markets - estimated in the billions of dollars.

In Michigan, Detroit Edison is on track to become the world's first utility to install superconducting cables as part of its electrical distribution grid. The demonstration project involves high-voltage cables installed within a Detroit substation. The first current will flow through them in 2000.

In California, Southern California Edison is planning to test at a Los Angeles substation a superconducting device designed to smooth out sudden spikes in current along distribution lines. Such devices, known as fault current limiters, could prevent problems ranging from temporary local blackouts caused by lightning to cascading regional blackouts.

In North Carolina, Carolina Power and Light Company in Raleigh, is offering commercial customers superconducting magnetic storage devices that keep momentary surges and sags in electric power from bringing a company's assembly lines to a costly halt. The downtime from such outages is estimated to cost industry $12 billion a year.

Meanwhile, in Europe, Electricit de France and the Swiss firm ABB are developing superconducting high-voltage transformers and hope to have a prototype installed and tested in an EDF substation by the end of 2000.

"In the next year, we'll see a lot of prototypes operating," says Dean Peterson, who heads the Superconducting Technology Center at the Los Alamos National Laboratory in New Mexico. "It's going to be pretty exciting."

In the United States, the potential payoff from cable alone is enormous, analysts predict. "The [Department of Energy] recently estimated that if utilities changed all of their existing transmission and distribution lines and replaced them with superconducting lines that are 50 percent more efficient, they could save $6.5 billion a year," says Donald Von Dollen, of the Electric Power Research Institute in Palo Alto, Calif. The key to the savings lies in superconductors' ability to carry electricity with virtually no resistance losses. Currently, power plants have to generate enough electricity to compensate for those losses.

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Superconductors can be finicky, however. They must be cooled to sufficiently low temperatures to allow current to flow unhindered. If the temperature rises too high, or if superconductors face currents or magnetic fields that exceed certain thresholds, their resistance returns. Until 1986, commercial superconductors were made from materials that had to be chilled to 23 Kelvin (minus 418 degrees Fahrenheit) in order to operate properly. They have found a small, if profitable market, in specialized areas. Electromagnets made from these low-temperature superconductors, for example, are used in research applications such as particle accelerators and in hospitals for imaging the human body.

In Japan, the government has built a demonstration version of its high-speed bullet train that uses superconducting magnets to travel on a cushion of magnetic fields. Utility cables using low-temperature superconductors have been built and tested, but their cooling costs have been too high to give them much commercial appeal.

In 1986, however, researchers at an IBM laboratory in Zurich, Switzerland, discovered a new class of ceramic-like superconductors that lost their resistance at 35 K. Within a few months, scientists in the United States had found similar materials that lost their resistance to current at 92 K. At these temperatures, cooling becomes much more economical. Such "high temperature" superconductors form the basis for the cable Detroit Edison will test.

Indeed, the cables represent a turning point for high-temperature superconductors as a whole. "They are creating a market on a much more rapid time scale than anyone predicted," says Gregory Yurek, president of American Superconductor Corp., a Westborough, Mass., company that developed the wires for Detroit Edison's new cables.

In the Detroit project, announced last month as a US Department of Energy contract, three thinner superconducting cables with a combined weight of 200 pounds will carry as much electricity as the nine conventional cables they replace, which weigh 18,000 pounds.

Today, as states press forward with efforts to deregulate electric utilities, the most successful competitors will be utilities, generating companies, and distribution firms that not only can match low prices but can guarantee the quality and reliability of the power they deliver, Dr. Yurek says, adding that superconducting equipment for utilities holds the key to quality and reliability.

As much progress as wiremakers such as Yurek have made bending the new superconductors to fit their vision of the future, the price of the wire needs to drop further, says EPRI's Von Dollen.

Currently, Yurek's company is working with EPRI, Los Alamos, and the Oak Ridge National Laboratory to develop a new form of wire fabrication that uses a less costly recipe for high-temperature superconductors.

"The biggest commercial promise comes when you make high-performance wire that's really cheap," Von Dollen says. "If this pans out, all of the power applications become a lot more attractive. We're not there yet, but any day now."

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