(John Kemp is a Reuters market analyst. The views expressed are
By John Kemp
LONDON Nov 13 Much as the anger at continued
power outages in New York and other states hit by storm Sandy is
understandable, past experience shows a two-week wait is far
Thirteen days after the post-tropical cyclone hit the East
Coast, almost 90,000 customers were still without mains power on
Monday, the vast majority in New York state (80,000).
More than 8 million customers have already had their supply
restored. But for those still without light, power and in some
cases heat, lengthy delays restoring electric service have
become a source of mounting frustration and anger.
The Long Island Power Authority (LIPA) and Consolidated
Edison of New York (Con Ed), have borne the brunt of that anger
as the principal suppliers in New York City and Long Island.
However, lengthy re-connection delays for customers on
small, remote or badly damaged circuits are unfortunately common
after big storms.
On June 29, 2012, a major storm system known as a derecho
formed over Illinois and moved down the Ohio valley to the
Mid-Atlantic, with winds gusting up to 80-100 miles per hour.
The derecho blacked out power to 4.2 million customers
across 11 states and the District of Columbia, according to a
review of the outages compiled by the Infrastructure Security
and Energy Restoration (ISER) Division of the U.S. Department of
Five days later, more than 400,000 customers were still
without power in West Virginia (198,000), Ohio (97,000),
Virginia (72,000), Maryland (33,000) and other states. Small
groups of unlucky customers were still power-less 9 days after
the storm ("A review of power outages and restoration following
the June 2012 derecho" August 2012).
RESTORATION CURVE ANALYSIS
In the aftermath of a major outage, power suppliers and
policymakers study "restoration curves" to derive lessons from
the experience. Restoration curves plot the number of customers
still without power, or those reconnected, each day after the
storm hits (Charts 1 and 2).
Chart 1: link.reuters.com/haf93t
Chart 2: link.reuters.com/kaf93t
"There is no normal restoration curve following major
storms, as each event offers a unique set of conditions and
circumstances," ISER warns.
"However, utilities typically focus initial efforts on
repairing utility-owned power plants, substations and
transmission lines that serve them. Next utilities work to
restore customers that provide essential services to the
community, such as hospitals, police stations and fire
"Once essential customers are restored, utilities focus on
completing repairs to circuits that serve the largest number of
customers and can be restored in the least amount of time."
"After large circuits are repaired, restoration efforts
typically experience diminishing returns, as crews turn their
attention to circuits serving fewer customers. The final stages
of restoration often take the longest, as utilities restore
power to small groups and individual customers."
This is precisely the pattern which has been observed in New
York, New Jersey and Pennsylvania since Sandy hit (Chart 1).
On Nov 1, almost 350,000 customers had power restored in New
York state, but by Nov 7 daily restorations had fallen to
115,000, and by Nov 11 it was just 61,000.
In Pennsylvania, power was restored to 415,000 customers on
Oct 31, but by Nov 4 restorations had fallen to 81,000 and by
Nov 8 to 4,000.
Given that post-tropical storm Sandy took out power to
roughly twice as many customers as the June derecho, it is not
surprising some customers have so far had to wait about 1.5
times as long to have their power restored.
HARDENING AND RESILIENCY
Following the storm and flooding, many customers, utilities
and public utility commissions (PUCs) in the Northeast are
asking whether more could be done to strengthen the transmission
and distribution system to reduce outages from future storms.
In fact much has already been done in states along the U.S.
Gulf Coast and in the Southeast on making electricity systems
harder and more resilient following the devastating hurricanes
in 2005 (Katrina and Rita) and 2008 (Gustav and Ike) which
devastated the city of New Orleans and wreaked widespread havoc
on the region's oil refineries and communities.
The results are summarised in a lessons-learned report on
"Hardening and resilience: U.S. energy industry response to
recent hurricane seasons" published by ISER in August 2010.
The report documents measures which can be used to harden
power networks to make them less susceptible to damage from
extreme wind, flooding and flying debris: raising substations
and control rooms on the flood plain or relocated them to higher
ground, upgrading power poles from wood to steel, strengthening
poles with guy lines, and burying power lines underground.
Officials also talk about making networks more "resilient"
essentially a measure of their ability to recover more quickly
after a major storm. For example that can be bolstered by
conducting preparedness and training exercises, participating in
regional mutual aid groups to share linemen and equipment,
stockpiling spare transmission and distribution equipment, and
even purchasing or leasing mobile transformers and substations
that can be delivered by road.
GULF COAST HURRICANE LESSONS
As the Northeastern states contemplate how to harden their
electricity system in case of future storms, the question is how
much customers and utility commissions are prepared to order the
utilities to spend and recover through higher rates.
Following 2005 and 2008 hurricanes, public utility
commissions in traditional hurricane states Florida, Louisiana
and Texas have all introduced stringent new reporting
requirements and regulations for power companies covering
reliability, storm and flood preparations.
It is entirely understandable that New York, for which Sandy
was a once in a century occurrence, was less prepared.
The storm surge last month also appears to have done at
least as much damage as high winds, though in general wind
damage poses a greater threat to electrical assets according to
A category 1 hurricane (74-95 miles per hour) is likely to
result in "extensive damage to power lines and poles that will
likely result in power outages that could last a few to several
days" says ISER.
A category 3 storm (111-130 miles per hour) will mean
"electricity is unavailable for several days or a few weeks."
Any region hit by a category 4 or 5 storm is likely to see some
customers without power for months.
Even if transmission and distribution lines, poles and
towers are designed to withstand high winds, they are unlikely
to survive a strike by a 3 tonne tree flying at 120 miles per
Public utility commissions in Texas, Louisiana and Florida
have all demanded that poles in coastal areas be upgraded to
withstand winds of 140 or even 150 miles per hour. Poles can
also be guyed to cope with extreme winds at a cost of about
$1,500-3,000 per pole.
In the case of the high-voltage transmission circuits, Gulf
Power company guyed 300 transmission towers and other vulnerable
assets, and replaced wooden cross arms with steel ones, for a
total cost of about $600,000, according to ISER.
BURYING LINES, CUTTING TREES
Burying power lines is an extreme option. The frequency of
outages on buried lines is 50 percent less than for overhead
wires, but when they do go wrong outages last 58 percent longer.
But the catch is that burying does not necessarily protect
power lines from flooding and storm surges. It is also very
"Southwestern Electric Power Company estimated a 79 percent
premium for undergrounding, with the cost of overhead wires at
$250,000 per circuit mile and undergrounding at $447,200 per
circuit mile," ISER explained.
For major transmission circuits, the extra cost could be
much more. Louisiana power companies warned the state utility
commission that undergrounding high-voltage circuits would cost
5-10 times as much as overhead lines, $500,000 to $2 million per
mile, plus coolants and pumping stations to prevent the system
overheating (wires give off a lot of warmth). The state's
utilities put the total cost of conversion at $1,500-4,500 per
More cost effective is raising substations and control
centres to protect them from flood damage. The Public Utility
Commission of Texas (PUCT) recommends all new substations
located on a 100-year floodplain be raised so the floor of the
control house and all water-sensitive components above the
100-year flood level.
The single most useful resiliency measure, however, is
keeping trees and vegetation near power lines well trimmed.
"Tree and vegetation-related damage to power lines is the
most common cause of electricity outages," ISER warns, not just
for local low voltage circuits but for the major inter-regional
distribution system as well.
Uncontrolled tree growth was significantly responsible for
the giant August 2003 blackout that left 50 million people
without power in the Northeast for up to four days. Every
utility, says ISER, should have a formal vegetation management
(Editing by Patrick Graham)