Undergrounding vs. Overhead lines
Electric utilities sometimes face obstacles in the siting process of
overhead transmission lines because lengthy stretches of land –
known as rights-of-way – are required for construction. Many
people would prefer to receive electricity without ever seeing how it
gets to their home or business. This is especially true in particularly
scenic or historic areas, and in heavily populated areas. To
eliminate the visual impacts of overhead transmission lines, some
industry observers believe that transmission lines should routinely
be buried underground.
The pros and cons of undergrounding
Placing transmission lines underground can ease the challenges of
siting major transmission projects by eliminating visual impacts.
Underground transmission lines are also less susceptible to
outages caused by severe weather.
However, there are other factors policymakers should be aware of
when considering the feasibility of underground transmission.
First, underground transmission projects cost many times more
than the equivalent overhead project. In most instances, installing underground lines is more intrusive because of the need to cut roads and sidewalks, dig a trench,
refill a trench, and repair the surface.
Underground lines also must be routed to avoid gas, water and sewer lines and wetlands, all of
which can add time and cost to construction.
When an underground line endures some
kind of fault, the outage is usually longer
because it cannot be identified and
isolated as easily as an overhead line. In
addition, the process to repair the cable is
more time-consuming, resulting in longer
outages and an increased reliability risk.
Underground lines are less efficient at
carrying electricity, so they must be short or
use expensive methods to improve the flow
The combination of higher construction costs and maintenance and
reliability problems have resulted in underground transmission
representing just a small fraction (<1%) of all transmission lines.
None of these concerns rule out the use of underground
transmission lines completely and there are circumstances where
underground is the appropriate choice (in urban settings and near
airports, for example).
However, regulated utilities are obligated to prove their costs are
“just and reasonable” to a state utility commission. All factors, with
cost being at the forefront, must be considered when evaluating
options for transmission lines.
AEP understands there are
situations that require
transmission lines be placed
underground, but the higher
cost of constructing, repairing
and maintaining underground
transmission lines effectively
prohibit their routine use.
AEP will build underground
transmission lines when it is the
economically and technically
appropriate solution. If
underground lines are
technically feasible and will
maintain reliability, AEP will
consider placing transmission
lines underground when a third
party absorbs the costs instead