High temperature superconducting (HTS) cables have gained attention in the last couple years as a solution to the shortage of transmission capabilities. Superconductors are materials that lose their resistance to the flow of electrons when cooled to temperatures close to absolute zero – hence, they conduct electricity almost ideally. European researchers initiated the ‘Super coated conductor cable’ (Super3c) project to develop, manufacture and test a 30 meter prototype system expected to be the first in the world based on low-loss HTS cable technology using CC tapes.
Several High temperature superconducting (HTS) cable prototypes have been manufactured in the world with HTS bismuth-based multi-filamentary wires as current carrying elements. This technology is now moving towards the pre-commercial stage through already announced or under discussion multi-hectometre cable projects. However, these multi-filamentary wires are expected to be replaced in the near future by a generation of cheaper HTS tapes, the Coated conductors (CC). According to their final report, SUPER3C is one of the first cables in the world using second generation (2G) HTS tapes as current carrying elements. The 2G-hybrid conductor utilises the advantages of both superconductivity and copper, enabling it to work and interconnect smoothly with conventional network components.
30 meter prototype of the Super Coated Conductor Cable (expected to be cheaper than multi-filament superconductor wires
EU cordis – Super Coated Conductor Cable
The project aimed at establishing the feasibility of a HTS power cable using CC tapes. It comprised the development, manufacturing and testing of a functional model consisting of a one-phase, 30-meter long cable system targeting a 1 kA current at 10 kV for a transmitted power of 17 MVA.
The feasibility of the High temperature superconducting (HTS) cable technology was proven through several projects using Bi2Sr2Ca2Cu3O10-x multifilamentary HTS tapes as current carrying elements. Lengths up to 600 meters, voltages up to 138 kV, currents up to 3 kA were demonstrated. This technology is now moving towards the pre-commercial stage through kilometric cable projects. However, expensive multifilamentary HTS tapes are expected to be replaced in the near future by the second generation of HTS wires, the YBa2Cu3O7-x (YBCO) Coated conductor (CC) tapes, which, through a lower production cost, will allow for a wider use of HTS cables. These CC tapes exhibit a multilayer structure which consists of a metallic substrate covered by a few buffer layers, the YBCO HTS layer and a thin metallic cap layer.
After an extensive modelling program, cable and terminations designs were validated through the test of prototypes. In parallel, a HTS-copper hybrid CC tape was developed using Alternating beam assisted deposition (ABAD) and High-rate pulse laser deposition (HRPLD). The main deliverable, the 30-meter one-phase functional cable model, including terminations and liquid nitrogen cooling system, was manufactured and successfully tested through an extensive program including short-circuit tests up to 40 kA during 1s. The 17 MVA target was met through a voltage of 20 kV and a current of 0.5 kA.
The work carried out within the framework of this project also provided a much clearer vision of how superconducting cables could be integrated in power grids and how they compare with conventional technologies on an economical standpoint. The SUPER3C functional model has been one of the first HTS coated conductor cable in the world and has positioned Europe in the leading group for that technology.