Compact high-temperature superconducting cables demonstrated at NIST

February 11, 2011, National Institute of Standards and Technology
Cross-section of a high-temperature superconducting cable design invented at NIST. In the center are copper wires bundled with nylon and plastic insulation. The outer rings are a series of superconducting tapes wrapped in spirals around the copper. The cable is 7.5 millimeters in outer diameter. Credit: van der Laan/NIST

A researcher at the National Institute of Standards and Technology has invented a method of making high-temperature superconducting (HTS) cables that are thinner and more flexible than demonstration HTS cables now installed in the electric power grid while carrying the same or more current. The compact cables could be used in the electric grid as well as scientific and medical equipment and may enable HTS power transmission for military applications.

Described in a paper just published online,* the new method involves winding multiple HTS-coated conductors** around a multi-strand copper “former” or core. The superconducting layers are wound in spirals in alternating directions. One prototype cable is 6.5 millimeters (mm) in outer diameter and carries a current of 1,200 amperes; a second cable is 7.5 mm in diameter and carries a current as high as 2,800 amperes. They are roughly one-tenth the diameter of typical HTS cables used in the power grid. (Standard electrical transmission lines normally operate at currents below 1,000 amperes.)

HTS materials, which conduct electricity without resistance when cooled sufficiently (below 77 K, or minus 196 C/minus 321 F, for the new cables) with liquid nitrogen or helium gas, are used to boost efficiency in some power grids. The main innovation in the compact cables is the tolerance of newer HTS conductors to compressive strain that allows use of the unusually slender former, says developer Danko van der Laan, a University of Colorado scientist working at NIST.

“The knowledge I gained while working at NIST on electromechanical properties of high-temperature superconductors was very important for inventing the initial cable concept,” van der Laan says. “For instance, my discovery that the conductor survives large compressive strains made me realize that wrapping the conductor around a small diameter former would most likely work.”

Van der Laan and NIST colleagues demonstrated the feasibility of the new concept by making several cables and testing their performance. They used an HTS material with a critical current that is less sensitive to strain than some other materials. Although the prototype cables are wound by hand, several manufacturers say mass production is feasible.

NIST researchers are now developing prototype compact HTS cables for the military, which requires small size and light weight as well as flexibility to pull transmission lines through conduits with tight bends. Beside power transmission, the flexible cabling concept could be used for superconducting transformers, generators, and magnetic energy storage devices that require high-current windings. The compact cables also could be used in high-field magnets for fusion and for medical applications such as next-generation magnetic resonance imaging and proton cancer treatment systems.

The work was supported in part by the U.S. Department of Energy.

Explore further: Widespread use of high-temperature superconductors on horizon

More information: * D.C. van der Laan, X.F. Lu, and L.F. Goodrich. Compact GdBa2Cu3O7-δ. coated conductor cables for electric power transmission and magnet applications. Superconductor Science & Technology. 24 042001, doi: 10.1088/0953-2048/24/4/042001

** The superconducting compound used in the work is gadolinium-barium-copper-oxide, or GdBa2Cu3O7-δ.

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1 / 5 (2) Feb 11, 2011
When did 77K become high temperature? :-p Its good to see that there is effort to develop superconducting wires, they hold a lot of future potential
5 / 5 (1) Feb 11, 2011
it's high enough that it doesn't cost an arm+leg to cool it. and by shrinking the diameter of the cable while simultaneously increasing the current, and you go along way to helping make a superconducting grid.
1 / 5 (1) Feb 11, 2011
Personally, i have strong doubts about the feasibility of true room temp superconductors. Maybe they squeeze another 50-100k in the next 50-100 years, but you're never going to have a superconducting chip in your cell phone.
5 / 5 (5) Feb 11, 2011
Liquid nitrogen is a generic, renewable commodity, unlike Helium which is rapidly being depleted...

I'd prefer my superconductors to run at -40'C/F, but I'd settle for 77K if it tolerates a very large current...
not rated yet Feb 11, 2011
WHy can't i pass the darm spam filter ???

this keeps track of the superconducting world -- the record as 'I believe' has been verified independantly is at 278K or -5C which is high enough to scream about -- but until this gets further research it means nothing. This is hot news in the SC world.

go to this site:

i had to take off the www and the http:// to get this to post -- sorry
not rated yet Feb 11, 2011
Worst spammer ever.
not rated yet Feb 12, 2011
There has to be a molecular structure that allows Cooper pairs to become ballistic at room temperature. Tuning the recipe may take years, but there is nothing magical about our planet's average temperature that prevents superconductivity.

Can't some ambitious programmer write a genetic algorithm to evolve a superconducting material? If BOINC can test molecular binding sites, why can't something similar be done for plain old bulk materials?
not rated yet Feb 12, 2011
jimbo92107. a good starting place for your research project would be reviewing the available literature. you may be surprised by how long intensive research in this field has been carried out.
not rated yet Mar 03, 2011
Personally, i have strong doubts about the feasibility of true room temp superconductors. Maybe they squeeze another 50-100k in the next 50-100 years, but you're never going to have a superconducting chip in your cell phone.

Uhh... you do realize the record for S.C.'s is about 250k, you squeeze an extra 50-100k and you're looking at over room temp or about room temp if you take the low end of that , for super conductors... so your statement is kind of fail...

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