Superconducting fault current limiter improves short-circuit strength of power gridsEU Project ECCOFLOW
In the context of Germany’s energy turnaround the change of electricity generation structures has increased risks for reliable distribution network operation. Superconducting fault current limiters can protect distribution networks and medium-voltage components against short-circuit currents. The devices offer a new protection mechanism which improves both security and availability. Switchgear and other network operating equipment can thus be designed to lower short-circuit strength requirements which is more cost effective. Possible applications of superconducting fault current limiters include:
• enabling of busbar couplings while retaining switchgear in place
• protection of generator or transformer feeders
• protection of local distribution and decentralised-generation networks
• enhancing grids for additional electricity feed-in without increasing the short-
Resistive superconducting fault current limiters are “electrically neutral” in regular operation. In this state, the superconductor material shows practically no electric resistance at temperatures of about –200 °C. “Critical currents” exceeding the nominal level, however, will cause the material to instantly build up high electric resistance. This current limiting function is a result of the material’s physical properties only. As a consequence, the superconducting fault current limiter does not require detection and resets automatically.
First devices are being operated in the UK distribution network, while in Germany, Vattenfall has successfully completed field trials of two superconducting fault current limiters at its Boxberg power plant. The ECCOFLOW project which involves Nexans and 13 other partners now provides the framework for an installation that will emphasise the suitability of the resistive fault current limiter for export. The device was designed and built by Nexans SuperConductors GmbH in Hürth, Germany, and shipped for type testing in late 2012. The ECCOFLOW limiter is the first design to match a wide range of grid environments and functional demands. It is scheduled for six months deployment in an Endesa substation in Palma de Mallorca (Spain) and subsequent installation in the Východoslovenská Energetika network in Košice (Slovakia).
Nexans Deutschland GmbH
Dr. Joachim Bock
Director Sales and Market Development HTS Systems Nexans