Modular Superconducting Cable Qualified for 10kA Currents with 3.2GW Power Transmission

June 12, 2019 by Scott McMahan

A group of 10 academic and industry partners of the EU-funded Best Paths project have developed a new modular HVDC superconducting cable system for bulk power transmission over long distances with minimal resistive losses. Nexans, which led the project, reported that it tested and qualified the high-voltage dc superconducting cable that the project created for 320kVdc for currents up to 10kA with a 3.2GW power transmission capability.

Superconducting cables could help enable Europe's power grids to meet their challenging CO2 reduction targets by enabling the transfer many gigawatts of electricity over distances of several hundreds of kilometers without the losses associated with conventional resistive cables. Such cables could transfer power from remote solar or wind farms to population centers.

Nexans has helped to bring these high-power superconducting cables a step closer to reality with the successful completion of qualification tests on the Best Paths superconducting cable created for high-voltage dc links.

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Notably, a number of superconducting cables are already operating in ac networks.

However, the EU-funded Best Paths project has focused on the research and development of modular HVDC solutions for bulk power transmission.

According to Nexans, the superconducting cable developed for the project is easily adaptable so the rated current and voltage can be matched to any power grid specification.

Nexans lead the project with nine other industrial and academic partners including CERN, Columbus Superconductors, ESPCI Paris, Ricerca sul Sistema Energetico (RSE), Karlsruhe Institute of Technology (KIT), IASS Potsdam, Réseau de Transport d'Électricité (RTE), Technische Universität Dresden, and Universidad Politécnica de Madrid (UPM)

The Best Paths project culminated with the first successful qualification (on a test platform) of a full-scale 320kV HVDC superconducting loop. This loop was comprised of two terminations and a 30 meter length of cable carrying a current of 10kA for a rated power transmission capacity of 3.2GW.

The program included a complete sequence of voltage testing at 1.85 times the rated voltage (up to 592kV) and impulse tests.

The Best Paths superconducting cable is based on magnesium diboride (MgB2), a simple compound using raw materials that are abundant in nature. According to Nexan, the compound is easy and inexpensive to produce, providing a substantial cost benefit compared to other relevant superconductor materials with the need to cool at a lower temperature. The cable is housed in a thermally insulating cryostat cooled by helium.

The primary advantage of superconducting cables in HVDC applications is their ability to carry high currents for transferring very large amounts of power with minimal losses. This high power capacity gives it a very compact installation footprint in the range of one meter in width for a dipole carrying 6.4GW. However, a traditional circuit based on XLPE insulated copper cables would typically have to be 10 meters wide. This footprint reduction by a factor of 10 offers significant cost savings and makes it easier to obtain permits for rights-of-way.

"Participation in the Best Paths project has further reinforced Nexans' leading position in superconducting cable technology and the new HVDC cable system is an important addition to our portfolio of technical solutions to increase the integration of renewable energy resources in Europe's power grids," says Dr. Christian-Eric Bruzek, Project Manager at Nexans.

"In the longer term, we expect HVDC superconductor cables to carry power over hundreds of kilometers. But in the short term we see them as part of an overall solution alongside conventional overhead lines and underground cables, helping to create corridors in challenging installations such as when crossing rivers, in congested urban areas or where environmental impact must be minimized."

While the Best Paths project targeted HVDC applications, the same cable technology could be employed in ac applications with ultra-high voltage levels of up to 400kV.

Development and testing of the Best Paths cable involved Nexans facilities in Calais(France), Hannover (Germany), Cortaillod (Switzerland), and Halden (Norway).