A new circuit breaker design for high-voltage direct current means supergrids connecting resources on a global scale will be more efficient and reliable.
Supergrids connecting electricity networks and renewable energy resources on a global scale will be more efficient and reliable, thanks to a new circuit breaker design for high-voltage direct current [HVDC] power lines, recently unveiled by the Swiss technology corporation ABB.
The breaker means power flow equivalent to the electrical output of a large power station can be interrupted in just five milliseconds – 30 times faster than the blink of an eye – protecting against overloads which cause damage and cuts.
“A circuit breaker is the key to building HVDC networks, as they need an elegant mechanism to force the current to zero”, says Kang Li, a professor at Queen’s University Belfast’s School of Electronics, Electrical Engineering and Computer Science. “Reliability is the big issue, and ABB’s HVDC breaker represents a big step forward.”
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Joe Hogan, CEO of ABB, explains that DC grids will be able to interconnect countries and continents, balancing loads and reinforcing the existing alternating current [AC] transmission networks. “This breakthrough will make it possible to build the grid of the future”, he adds. While high voltage technology has been around for almost 60 years, HVDC lines have been notorious for turning local power disruptions into widespread outages.
The absence of an effective circuit-breaker has limited current high voltage transmission mostly to point-to-point power lines, with AC grids used for longer hauls. However, with this safety feature in place, DC’s greater efficiency – up to 50% over long distances – could make transmission between countries and across continents more economic. The potential to run DC cables both underground and underwater means existing AC grids can be linked both to each other and to far-flung renewable energy sources, reducing reliance on fossil fuels, and boosting prospects for global trade in electricity from renewable sources.
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The HVDC transmission lines will help to connect renewable energy generated in many different locations, says Claes Rytoft, Head of Technology at ABB’s Power Systems Division: “Take Europe, for example. We have hydro in Scandinavia and the Alps, we have wind in the North Sea, and we have sun in the south. If you really want to optimise the use of these energy sources you need a very strong transmission backbone, and there we believe DC is the right choice.”
Kang Li is enthusiastic about the potential for wind energy: “The European Wind Energy Association estimates that 120GW of offshore wind power will be installed in the next two decades,” he says. “The integration of offshore wind farms into the existing electrical grid has brought several technical challenges, renewing interest in HVDC networks which draw little capacitive current compared with the high voltage AC solution.”
By. Ian Randall