Project Aims to Commercialise Cheaper Coated Conductor HTS Tapes

The development of High Temperature Superconducting (HTS) wires during the last two decades allows to envision large scale applications. Among them, power cables constitute a straightforward way to take advantage of the very high current densities achieved in HTS materials.

The basic features of HTS cables are their ability to transport power at a lower voltage than conventional cables, which drastically diminishes the reactive power and the energy losses, and their low impedance, thus allowing direct linking of substations saving transformers and simplifying the grid. Larger amounts of power can be transmitted more efficiently with lower losses. The HTS cables are also inert for the environment. They do not generate any external magnetic field, thanks to a superconducting shield, and their excellent thermal insulation eliminates any temperature impact on the cable surroundings and any heat exhaust constraint. As a consequence, HTS cables need a minimized space and can be installed, retro-fitted, in existing right-of-way or ducts.

HTS cable prototypes have been manufactured around the world with HTS bismuth-based multi-filamentary wires as current carrying elements. This technology is now moving towards the pre-commercial stage. However, these multi-filamentary wires are expected to be replaced in the near future by a 2nd generation of cheaper HTS wires, the Coated Conductor (CC) tapes. Several CC-based HTS cable projects have been or are being carried out around the world. Among them, the EU-funded project SUPER3C allowed thirteen European partners to develop a medium voltage cable using the latest and most promising type of superconducting wires, the coated conductors.

The SUPER3C project aims at establishing the feasibility of a low-loss HTS energy cable using CC tapes. It comprises the development, manufacturing and testing of a functional model consisting of a one-phase, 30-meter long, 17 MVA (10 kV, 1 kA) cable with its terminations.

The project, carried out from June 2004 to December 2008, involved thirteen partners from six countries and was coordinated by Nexans France. The Tampere University of Technology (Finland) led the cable modelling task with the support of the Bratislava Institute of Electrical Engineering from the Slovak Academy of Sciences in Slovakia, which was in particular in charge of fabricating the short cable models, and the Göttingen Center for Applied Materials Development (ZFW GmbH, Germany) for CC tape architecture and characterization. European High Temperature Superconductors (Bruker HTS, Germany) led the CC tape development and manufacturing task with support from Nexans SuperConductors (Germany) and from the Barcelona Institute of Materials Sciences (ICMAB, Spain). The functional cable model manufacturing task was led by Nexans Deutschland (Germany). Nexans Norway fabricated the cable core which was introduced in the flexible cryogenic envelope. The cable terminations were provided by Nexans France. Labein Tecnalia (Spain) led the cable testing and the network integration task, with support from E.on Engineering. Air Liquide (France) supplied the liquid nitrogen cooling system allowing the CC tape to reach its superconducting state around –200°C. E.on Energie (Germany) led the technical, economical and social assessments.

The project resulted in a one-phase 30-meter cable system which was submitted to a full characterization program including 24 kV class dielectric tests and short-circuit tests up to 40 kA for 1 second. Due to improved design of internal cable architecture, the targeted transmitted power of 17 MVA was demonstrated by lower number of CC tapes and higher dielectric properties.

The project also addressed through several case studies the integration of HTS cables in power grids as well as their social and economical impact. The study allowed the partners to identify the most promising scenarios for integrating HTS cable systems in power grids.

Being an extraordinary technological challenge for the future development of superconducting applications in power grids, the project has achieved most of its objectives and technical goals showing a high degree of interaction between all the partners.

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