SUPERCABLE ON THE WAY

ELECTRICITY: Nine of the world’s largest copper electricity cables are required to transmit 3,000 kW of electricity. One new supercable from Denmark’s NKT Cables can replace all nine, while at the same time avoiding the energy loss of copper cables

Dag Willén, head of development at NKT Cables, with the one supercable which will replace nine heavy copper cables

Economic growth and the world’s insatiable need for more energy has put the energy industry under pressure. One problem is the production of energy itself, whether from conventional or renewable energy sources. Another problem is transmitting the energy, especially in big cities where there is no more space available underground for laying electricity cables, and where costs are rapidly rising.

The solution is the HTS supercable, a single cable which can replace nine of the largest copper cables while saving around 75% of the energy loss which inevitably happens in a copper cable because of its intrinsic resistance.

Denmark’s NKT Cables a/s is the world’s first cable manufacturer to offer the supercable on a commercial basis. After more than 20 years of research in superconductor technology and more than six years of practical use in various pilot projects, the first TRIAX superconducting cable is coming on the market.

Conducting at minus 200°C

“Those teething problems that any new technology naturally generates have been solved,” says Dag Willén, head of development at NKT Cables. “The fine adjustments have been made, and the price of the individual cable components is rapidly on their way down. We are now close to the point of intersection where the price of a conventional copper cable and a supercable meet.” HTS (high temperature superconductor technology) is a young technology based on the discovery of a ceramic material which becomes superconducting when it ^{is cooled down to minus 200}°^{C. In addi}tion to being able to transport around five times as much capacity as conventional copper cables, the voltage loss has been reduced to a tenth.

“The cable is built around three phases with a core through which liquid nitrogen flows,” says Dag Willén. “The cable has some small built-in pumps which distribute the nitrogen around the phases. The whole process takes place

continuously, and the energy loss mainly comes from the energy that runs the pumps.” The first time that NKT Cables put its supercable into commercial use was in a transformer station in Copenhagen in 2001. The 30 metre long cable made it possible to avoid building a completely new transformer. It has been working ever since without problems, while NKT Cables’ technicians have refined the cable to its current form. The second generation cable is now deployed in a number of projects in New York and in Columbus, Ohio. In addition, the so far longest cable of six kilometres is to be installed in Amsterdam, the Netherlands.

Ready for mass production

“All around the world, electricity companies are probably among the most conservative when it comes to taking new technology into use,” says Dag Willén. “To them, security of supply is paramount and so they prefer well-known and thoroughly tested material. We have proved that HTS technology works, and that it is far more reliable at intermediate voltage than conventional cables at high voltage. The supercable does not require extra space underground, but can be installed as a direct replacement of existing copper cables, while at the same time removing the necessity for a number of transformer stations across the entire cable grid. Briefly stated – a lot more energy in a loss less space.

Dag Willén believes that the breakthrough for HTS technology as the future carrier of large amounts of electricity will come with the three ongoing projects, which will lay the foundation for making the supercable really competitive.

 “The future now lies in the production phase itself – upscaling production and optimising all the cable components. The cable is already transitioning from development laboratory to actual large-scale production. And we are right at the cutting edge, ready to deliver.”

http://www.nktcables.com

New York has an insatiable appetite for electricity. But each time new supplies are needed by the city, it requires costly new systems and enormous investments in transformer stations and cables. A joint venture between NKT Cables and America’s Southwire is now supplying a new type of HTS cable for the electricity company ConEd in New York. The cable can be installed without expensive excavation and at the same time removes the necessity for several current transformer stations, thus freeing up valuable new lots of land.

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