Super-fuse

A UK research project led by Rolls-Royce plans to use superconducting materials to protect electrical networks from sudden damaging surges in current.

The project team aims to develop a superconducting fault current limiter (FCL) which can act as a new type of self-resetting, solid-state fuse for heavy electrical equipment and power networks. The FCL under development will use magnesium diboride (MgB2) as its superconducting material. Rolls-Royce will work with Cambridge-based Diboride Conductors – one of only a handful of companies in the world working with the material – during the three-year programme.

Philip Sargent, managing director of Diboride, said the properties of superconducting materials make them ideal for protecting power networks from the sudden surges that occur when a fault hits the system.

At present, transformers and switchgear have to be designed to cope with current of up to 30 times the normal level simply to deal with faults.

This fault current could be reduced to just three or four times normal by using a superconducting FCL in the role of a fuse, according to Sargent. ‘If you get a current pulse or spike, it would stop superconducting and become a normal conductor and you would get an increase in resistance. There is nothing else which cuts out so completely and so quickly.’

This would not only give the networks better protection but also mean they do not have to be so drastically over-designed in the first place.

‘Electrical products are over-specified, and if you can remove the need for that the capital saving would be immense,’ claimed Sargent.

MgB2 was developed as a superconductor in Japan in 2001. According to Sargent, the material has the potential to overcome the major obstacle that has prevented the widespread application of superconductors to powernetworks – their prohibitive cost. Most materials currently available cost around $200 (£120) per metre, making them too expensive for anything but specialist niche applications.

Sargent said a superconductor begins to become economical for more widespread use in the $10-$20 per metre range, which he claimed was achievable with MgB2.

The project partners believe the development of the MgB2 FCL will coincide with a need for a major overhaul of the UK’s electricity infrastructure to deal with new power generation technologies such as wind, solar and tidal.

The initiative – which also includes electrical equipment manufacturer VA Tech and Cambridge University – signals the growing interest of companies such as Rolls-Royce in superconducting technology. The finished device will be installed on a ship based at the New and Renewable Energy Centre at Blyth, Northumbria. The centre is being built on the site of a former coal port to test a range of new power generation and energy-efficient technologies.

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