* ABB says beats rivals Alstom, Siemens in breakthrough
* High voltage circuit breaker could improve green energy
* Says solves DC current conundrum from birth of electricity
(Adds detail, background)
By Caroline Copley and Chris Wickham
ZURICH/LONDON, Nov 7 Swiss firm ABB
announced a breakthrough in technology to carry electricity over
long distances, making desert solar plants and ocean wind farms
much more viable.
Its new circuit breaker makes it easier to send electricity
through high-voltage direct-current (DC) lines into the grids
that link power stations to consumers, the engineering company
said on Wednesday.
DC lines are much more efficient over long distances than
the alternating current (AC) lines that are largely used at the
moment. They are also more compatible with some forms of
renewable power generation.
But using DC lines widely has been impractical without a
heavy-duty circuit breaker that can cut power when need be.
The search for such a circuit breaker has taken more than
100 years and ABB has been battling rivals Alstom and
Siemens to invent one first - potentially giving it
an important advantage in what it hopes will be a multi-billion
dollar market for DC grids.
"If they've managed to do this it's very significant," said
Roger Kemp, an engineering professor at Lancaster University in
northern England. "DC transmission is a much higher efficiency
way of moving electricity around."
It could bring closer the idea of huge solar power arrays in
the Sahara Desert supplying electricity to Europe, Kemp said.
ABB Chief Executive Joe Hogan hailed what he said was "a new
chapter in the history of electrical engineering."
High voltage DC is already used to connect wind farms to the
power grid and for delivering power to offshore oil and gas
platforms. But without a breaker, its use is very limited.
If you try to switch off direct current at the very high
voltages needed for power transmission, it can cause a spark
across the switch which simply keeps the electricity flowing.
That is not a problem with alternating current because there is
a window to interrupt the flow.
STOPPING A TRUCK
The challenge of breaking direct current can be compared to
quickly stopping a truck hurtling down a highway at top speed,
ABB's chief power engineer, Claes Rytoft, said.
ABB's circuit breaker works by combining mechanical and
power electronics that are capable of interrupting power flows
equivalent to the output of a large power station within five
milliseconds - 30 times faster than the blink of a human eye.
Conventional AC grids are also not compatible with the DC
power produced by many renewable sources, particularly solar
energy. Computers, televisions and mobile phones also run on DC,
meaning electricity has to be converted from AC.
The two systems have been at odds since their proponents,
Nikola Tesla and Thomas Edison, battled for supremacy in the new
technology a century ago.
Edison even electrocuted an elephant to highlight the
dangers of Tesla's AC power, but his rival's system took off
because it could transmit electricity further. At the time, DC
power couldn't carry power beyond a few city blocks.
High voltage DC can transmit 30 to 40 percent more energy
than conventional overhead lines carrying alternating current,
however, making it a better option for bringing power from
ABB is in talks with utility companies to identify pilot
projects for the technology over the next 12 months.
ABB has already installed a 2,000 km (1,250 mile) line in
China that operates DC power while a 2,375-km HVDC project under
construction in Brazil will be the world's longest such
transmission line when it comes online in 2013.
In Europe, high voltage DC is currently used to connect
Britain and the Netherlands. The island of Majorca, whose
tourists push up power demand every summer, was hooked up to the
Spanish mainland in September 2011.
(Editing by Matthew Tostevin)