FCL/B: An Integrated VSC-HVDC Fault Current Limiter/Breaker

Multi-terminal DC networks and meshed DC grids have been advocated by transmission utilities, industry and academe, as a potentially more cost effective means of integrating offshore renewable energy than point-to-point links. National Grid's Electricity Ten Year Statements and the European Network of Transmission System Operators for Electricity's Ten Year Network Development Plan as well as studies by The North Seas Countries' Offshore Grid Initiative all support this view.
To realize such HVDC networks, DC circuit breakers are necessary to isolate faulted DC sections. The unacceptable alternative would be to temporarily de-energise the whole DC network to then allow isolation of the faulted section. This is unacceptable because the resulting simultaneous loss of supply to the AC system would radically exceed onshore network design limits and would lead at least to severe disruption among consumers. For larger DC grids and power loss it would even cause widespread black-outs.
ABBs proactive HVDC circuit breaker comes close to the required efficiency and operational speed and indeed provides a solution for some cases. However it is fairly large, especially when the series 100mH inductor it requires to operate is considered. It is also appears to be targeted at a 5ms operating time, and commentators have indicated the need for protection against frequent faster events. The fastest such events have a rate of rise of current that requires breaking action in 2ms. A faster, smaller, cheaper solution is therefore still needed to enable offshore location of circuit breakers to allow offshore wind park integration.
This project will investigate novel designs integrating the circuit breaker with fault current limiter technology, which may thus be capable of achieving these size, speed and cost transformative targets.

The principle impact of this project will be the thorough assessment of the capabilities and multi-physics limits of superconducting Fault Current Limiters and HVDC Circuit Breakers for VSC-HVDC systems. DC circuit breakers form a bottleneck in the development of HVDC offshore grids, and if suitable devices are not available, the construction of large integrated DC grids will not be possible and more expensive solutions will be required. This project's research will thus majorly shape the development of DC offshore networks. The research will accordingly influence investment decisions in future networks by transmission utilities and design decisions by manufacturers, as well as influencing grid code development and system regulation decisions.

The project is also expected to generate IP in the form of new DC circuit breaker/fault current limiter component inventions and designs. This will be protected and developed through the intellectual property management arm of the University of Manchester (UMIP) either in the form of licensing, or should sufficient novelty arise, as potentially a spin-out company in partnership with project sponsors.

The potential expenditure on offshore VSC-HVDC networks is up to £30billion in just the UK, and just in the foreseeable future. Savings of up to one third (Peter Jones, ABB) are possible for getting the system 'designed right.' Making the right network design decisions is important - this proposal aims to ensure that the appropriate research as regards DC protection is available to inform such decisions.