Fault current limiter

Prototype superconducting fault current limiter using Magnesium Diboride wire

The control of fault current levels in land-based electrical power distribution systems is causing increasing concern. The rise in environmental and political pressure to increase the levels of distributed energy systems (DES) is leading to increased fault current levels that will require major system re-enforcement.

Superconducting coils offer significant potential as fault current limiters (FCL) but have suffered from high material/cooling costs and operational instabilities. Recently a new superconducting material – Magnesium Diboride – has been introduced that offers great promise as a low-cost, reliable current limiter. It can be produced in simple wire-form and the cooling requirements are reasonably easy. A simple resistive fault current limiter has been prototyped, under a Rolls-Royce led DTI project at Manchester, and has demonstrated effective and repeatable fault current action. The technology is very simple; the resistive wire-wound superconducting FCL presents negligibly small impedance to the system in the superconducting state. If a fault current rises above the superconductor critical current, it quenches in a sub-cycle response time to present a high resistance to the fault.

Prototype superconducting fault current limiter installed in cryostat ready for testing

The growing commercial potential of this work led to a £4M project funded by the Energy Technology Institute (ETI) to produce the first commercial Magnesium Diboride superconducting fault current limiters to operate on the UK distribution network. The project was announced by the Energy Secretary in July 2011 and the consortium partners include Applied Superconducting Conductors, Rolls-Royce, The University of Manchester, Western Power Distribution and E-ON.

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