Underground Construction - December 2017 - 10

By Jeff Griffin Senior Editor

Unique
Undergrounding Program
Reduces Outages, Maximizes Response Time

In late August, Hurricane Harvey
devastated Houston and other
areas in Southeast Texas, leaving
more than 750,000 customers
without electric power. Immediately after Harvey, Hurricane Irma
struck Florida, leaving much of the
state and more than 6 million customers in the dark.
Discussions about converting
overhead power lines to underground frequently occur after
every weather event that downs
lines and causes power outages.
New power lines have gone underground for decades, and outages
from weather-related causes can
be significantly less in areas were
infrastructure is buried.
"Why don't they bury them
where they'll be 'safe'," is an often-asked question following every
major storm-related outage.
But immediately after a major
storm isn't the time to begin planning an undergrounding program
- the priority is public safety and
restoring services as fast as possible. However, undergrounding is a
viable option for many power suppliers, and the number of carefully

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planned programs to replace aerial
infrastructure under the ground is
increasing.
Cost always has been the primary roadblock for undergrounding - it costs more to bury power
cable than to suspend it from
poles. However, considering
repeated replacements in stormprone areas, along with other
factors, many power companies
are considering ways to go underground in areas with older, established infrastructure.

Compromise
In Virginia, Dominion Energy has
had an underground program
underway for several years. Alan
Bradshaw, Dominion director of
electric distribution-underground,
said the company's Strategic Underground Program identifies the
most outage-prone areas with
overhead tap lines and targets
them for underground placement.
"The goal of the program," Bradshaw explained, "is to reduce the
number of work repair locations
required to restore power outages.
Our data suggest that converting

just 10 percent, or 4,000 miles, of
the most outage-prone lines could
reduce restoration times following
severe weather events by up to 50
percent."
Since July 2014, Dominion has
converted more than 650 miles of
outage-prone, overhead tap lines
to underground. This includes
more than 1,900 individual tap
lines across the company's Virginia
service territory.
Bradshaw said legislation
passed by the Virginia General
Assembly enables investor-owned
electric utilities to bury overhead
electric distribution lines that are
most prone to outages during
major storms, and to recover costs
for doing so. The law declares undergrounding outage-prone tap
lines to be in the public interest
and cost beneficial by providing
local and system level benefits for
customers.
Funding for the program comes
from a small rate adjustment
called a rider, which must be approved by the State Corporation
Commission (SCC) that monitors
the costs for the program. The

Strategic Underground Program
is subject to annual regulatory reviews and approvals by the SCC.

Evaluating the cost
Dominion's underground program
is based on research.
In 2003, Hurricane Isabel left
some Virginia customers without
power for more than two weeks.
Following that storm, Bradshaw
said the Virginia Corporation
Commission estimated the cost to
underground the overhead electric
distribution system in the state
would be $83 billion. Since that
time, costs will have increased.
"When we started to look at the
data," Bradshaw said, "we found
that a significant number of outage events occur on the tap line
portion of our distribution system.
"Looking deeper, we found
that over 60 percent of the outage
events that occur on tap lines actually occur on about 20 percent
of those tap lines, many located
in backyards with heavy tree canopies, exposing lines to damage
from trees."
Such areas are the most difficult
Underground Construction December 2017

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Underground Construction - December 2017

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