/images/PowerCableUpdate.jpg/images/southwire_100x70.jpgWorld-First Power Superconductor OnlineWorld1stPwrSuperconductorOnline.htmWorried about pushing more plant power through existing duct banks? A new option is on the horizon. Three Southwire plants in Carrollton, Ga., are now drawing power from the world's first working power-distribution application of superconductors.
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World-First Power Superconductor Online

Power-level superconductors go live in the world's First working installation.

Worried about pushing more plant power through existing duct banks? A new option is on the horizon. Three Southwire plants in Carrollton, Ga., are now drawing power from the world's first working power-distribution application of superconductors. "We officially threw the switch on February 18," says RL. Hughey, manager of the superconductor project. "The superconductors carried 60 percent of the plant load for 20 straight days."

The high-temperature superconductors, which run in circulating liquid nitrogen, performed flawlessly for the initial 20-day trial. Southwire engineers then took the line down for additions to the instrumentation system.

First runs were shared-load

"For testing purposes, we have three sets of cables carrying the 12.4kV service to these plants," Hughey says. "The overhead lines we're replacing, the superconductor lines, and a set of conventional underground lines. A typical plant load is 1,000A, and the design capacity of the superconductor is 1,250A."

When all three circuits work in parallel, the superconductors carry about 20 percent of the current. "You might expect the superconductors to carry more, but the resistance of the feeder lines and connectors is a factor in the load sharing," says Hughey. "When you take out the underground cables, which are quite large, the superconductor gets about 60 percent of the load."

 

"The commercial appeal of   superconductivity is the high current density it can provide." -RL. Hughey, Project Manager

 

More testing coming up

Hughey's team is running the entire plant load on the superconductors for a multi-week test.  "After the run at 100 percent, we'll run a series of tests where we have one or two phases running on the superconductors, and the other phases running on conventional cables," Hughey says. "We'll also experiment with raising the nitrogen temperature, to see what that does to performance."

While mixed testing and live online operation goes on, Hughey's team is continuing to develop the technology toward commercial uses.

"The commercial appeal of superconductivity is the high current density it can provide," Hughey says. "We expect the first applications to be in situations where it's prohibitively expensive to enlarge existing duct banks."

Low temperatures are high temperatures for superconductors

In the superconductor world, "hightemperature" is a very relative term. Liquid nitrogen boils at -321°F. What makes that a high temperature? Something even colder. Earlier superconductor technologies used liquid hydrogen at -423°F. That makes liquid nitrogen seem like a day at the beach.

Southwire's high temperature superconductor uses a bismuth-based ceramic material encased in a thin silver tape, which is wrapped around a flexible, porous pipe carrying liquid nitrogen. The pilot program conductors operate at 12.4kV above ground, and they use a fully shielded design similar to MV 90 power cable architecture.