(John Kemp is a Reuters market analyst. The views expressed are
By John Kemp
LONDON Nov 22 Businesses and households expect
reliable electricity to be available at the flick of a switch.
But the frequency of large-scale blackouts in the United States
has not fallen in the last 30 years, and big blackouts remain a
common occurrence throughout emerging markets.
The risk of massive failures affecting the supply to
millions of customers and darkening whole regions or countries
may even be increasing as demand rises, especially for air
conditioners, and electricity networks are integrated over
increasingly wide areas.
India's power failure earlier this year has heightened
concern about the reliability of power networks integrated over
wide areas, and raised questions about the wisdom of China's
plan for an ultra-high voltage super-grid.
On July 31, power cuts rolled across 22 states in the north
of India, which are home to 620 million people (and about 320
million electric customers), about 9 percent of the global
population. It was easily the biggest power outage in history.
Other mass blackouts recently have included the Java-Bali
blackout in Indonesia in 2005 (100 million people); the 2009
Brazil-Paraguay blackout (which left the whole of Paraguay and
parts of Brazil without electricity); and the 1999 South Brazil
blackout (75 million people).
But the advanced industrial countries are not immune --
though widespread failures are much rarer. In August 2003, a
blackout cut power to 50 million people across the Northeast
United States and neighbouring parts of Canada, in some cases
for up to four days.
Just a month later, in September 2003, a blackout cut power
to 4 million people across southern Sweden and eastern Denmark.
Five days after that, the whole of Italy was plunged into
darkness by a cascading power failure across the country's grid.
Blackouts are expensive. The August 2003 blackout in the
United States resulted in $3 billion of insurance claims,
according to one estimate.
But many insurance policies exclude power failure, and in
any event only cover the direct economic costs, not the
inconvenience and widespread disruption to daily life and
business activity. The total cost of the August 2003 blackout
was almost certainly many times the published insurance claims.
Restarting a network after a big blackout is no simple task.
Most power plants rely on power from the grid in their start up
procedure to work fuel and pumping systems and other control
equipment. Only a small proportion of power plants are equipped
with "black start" capability to begin generating power again in
the event the grid is lost completely.
In a sign that should worry policymakers, the frequency of
big blackouts does not appear to be falling despite heavy
investment on power transmission networks and improvements in
grid control systems.
In the United States, the frequency of major blackouts
(supply interruptions involving at least 300 megawatts or 50,000
customers) does not appear to have decreased between 1984 and
2006, according to one recent analysis of large-scale
interruptions ("Trends in the History of Large Blackouts in the
United States" 2008).
In fact, the risk may actually be increasing as a result of
changes in modern power system. Studies show the risk of failure
increases as demand on the grid rises and the margin of spare
capacity shrinks. In the United States, big power failures are
most likely to occur in late afternoon on hot summer or cold
winter days when air conditioning or heating demand is greatest.
Across much of the developing world, capacity margins are
shrinking as investment in generation and transmission struggle
to keep pace with burgeoning power demand. Low levels of spare
capacity contributed to India's mega-blackout this summer.
But margins are also shrinking in advanced economies as
coal-fired power stations are taken out of service and
market-based electricity systems fail to provide big enough
incentives to maintain large amounts of back up capacity.
In an further wrinkle, much of the growth in demand is for
airconditioning. There are concerns about the way in which the
modern high-efficiency motors used in many airconditioners
interact with the grid.
Many are exceptionally sensitive to a very brief drop in
voltage on the network and react in ways that can make the
voltage drop even worse -- known as microvoltage collapse.
"There is concern that these microvoltage collapse events
will begin to lump or interact together and cause large-scale
voltage collapse," the U.S. Oak Ridge National Laboratory wrote
in a 2008 report ("Local Dynamic Reactive Power for Correction
of System Voltage Problems").
In August 2003, it was a local voltage collapse in the
Cleveland-Akron area of Ohio, on a summer day, that helped pull
down the power supply to the entire U.S. Northeast
"These levels of airconditioning motor load truly present a
concern, because if several circuits stall at the same time, the
resulting level of inductive current flow may cascade into a
wider-scale voltage collapse," Oakridge warned.
Power supplies are being networked over wider and wider
areas, increasingly the risk a local problem will cascade across
the entire network and cut power to millions at a time.
The July 2012 blackout rolled across India's four northern
grids, which have been linked and synchronised in recent years,
highlighting the risks as well as benefits of interconnection.
The fifth grid, serving the south of the country, which is not
due to be synchronised until 2014, and was still relatively
isolated remained unaffected.
So the current fashion for connecting up local and regional
power networks to form national or even cross-national
super-grids may be unwitting making them more vulnerable to
China is a case in point. The country is building the
biggest super-grid of them all. State Grid Corporation is
lobbying the government to approve as many 20 ultra-high voltage
power lines criss-crossing the country, to help move power from
generators in the coal-rich north and northwest, and hydropower
from the gorges of Yunnan and Sichuan, to the main consuming
centres along the south and east coasts.
But critics warn it could also increase the risk of local
problems cascading across the national network and plunging the
entire country into darkness, as happened in India.
"The building of a large-scale long-distance ultra-high
voltage transmission system should be avoided," the Energy
Research Institute wrote in a recent report to the government's
powerful National Development and Reform Commission ("China
Energy Outlook" 2012).
"This kind of system is relatively fragile ... If all the
country's grids are connected by ultra-high voltage lines, if
the lines broke because of some natural or human incident, it
would result in a national power outage. The potential hazard is
In any event, some aspects of reliability, such as local
voltage collapse, are much easier to handle if there is plenty
of generation in the affected area, rather than relying on
transmission from distant generating units hundreds or even
thousands of kilometres away.
The August 2003 blackouts proved a wake-up call for
policymakers and grid companies; a lot of work has since been
done to improve grid management procedures and staff training.
The focus is likely to be redoubled following India's
dramatic problems this summer. China's State Grid has already
held a special conference to examine what lessons can be
But the truth is that the risk of major blackouts affecting
millions or hundreds of millions of customers at a time is
probably still increasing, as the rush to connect up networks
outstrips in improvements in control.
(Editing by William Hardy)