Superconducting fault current limiter benefits from Nexans technology

Voltimum Founder Member company Nexans has successfully completed performance testing on a new design of high temperature superconductor (HTSC) component developed for use in a superconducting fault current limiter (SCFCL). With a protected power of more than 130 kVA these are the world's most powerful components developed for SCFCLs so far:

The Superconducting Fault Current Limiter (SCFCL) is a new appliance for the power engineering sector. SCFCLs will considerably improve the resistance of power networks to short circuit currents. This will offer an important gain in the quality of the energy supply, especially as networks become more complex as a result of deregulation and the integration of renewable sources such as wind and solar energy.

When existing networks are extended, the capacity of the installed protection equipment is often exceeded by the additional fault power. In such cases, the use of a SCFCL unit can help to reduce infrastructure costs or even avoid the installation of new substations. The innovative SCFCL could also be of particular importance for projects such as the modernisation of the US power networks.

The design of the superconducting elements:

The superconducting elements, which form the core of the SCFCL, were designed and built by Nexans SuperConductors in Hürth (Germany), within the framework of an integrated project sponsored by the German Federal Department of Education and Science (BMBF). The high temperature superconducting components are bulk tubular parts based on a ceramic compound of Bi (Bismuth), Sr (Strontium), Ca (Calcium) and Cu (Copper) and produced by Nexans' own melt cast process. This is in contrast to HTS tapes or wires produced by the normal oxide powder in tube technology, as these are not suitable for use in SCFLs. The final components are cut into a double spiral providing a long active length with a compact design.

Successful testing:

The Nexans superconducting components were subjected to a variety of tests in the laboratories of the FGH (Research Association for High Voltage Technologies) in Mannheim/Germany and the FZK (Research Center in Karlsruhe/Germany). This included exposure to short circuit currents up to 18 kA and an artificial lightning impulse of 75kV. All tests proved the effective current limiting capability of the device without causing any defect to the superconductor. Nine components, connected in series, were capable of switching a total power of 1.2 MVA.

Further to these successful tests, Nexans SuperConductors is now working on a 10 MVA demonstrator for the 10 kV network level. This is scheduled to be completed by the end of 2003 and intended to be tested under field conditions by RWE (the German energy operator) in the German network.