Underground vs. Overhead Power Lines

There are two methods of installing the power lines that carry electricity to your home, overhead and underground. Lane Electric Cooperative members sometimes ask why we use one versus the other, or why all power lines are not installed using the underground construction method. These are great questions, and the answer is that each method has its place.

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Let’s look at some the advantages and disadvantages of each method.

Overhead

Overhead line construction starts with the setting of utility poles. Poles can be set in nearly any type of terrain, and are less expensive to build and maintain. Overhead lines are also easier to locate, and repair faults or damage. Once the poles are in place, wires can be strung and equipment installed.

Overhead lines are, however, more susceptible to extreme weather conditions, like wildfires and ice storms. As a part of our advanced wildfire mitigation planning, we are exploring additional options to make our system even more resilient, such as pole wraps, coated power lines and relocating overhead lines to less sensitive locations.

Pros:

• Less expensive to build and maintain
• Easier and quicker to locate and repair faults or damage
• Can be built in any terrain
• Faster construction time

Cons:

• Exposed to wind, wildfire and weather, including ice
• Susceptible to damage from trees and vegetation
• Vulnerable to blinks when animals and branches contact lines
• Risk of damage from vehicles colliding with power poles
• Possibility of contact with energized downed lines
• Less attractive

Underground

Underground line construction requires digging a trench that is deep enough to keep the lines well away from surface activities, like digging or construction. Where the terrain is extremely rocky, underground lines may not be an option. Wires are then laid in the trench directly or placed in conduits for protection. Currently, Lane Electric has more than half of our distribution system (754 miles of line) underground, which is significantly higher than the national average.

While underground lines are protected from wind, wildfires and tree branches, they are vulnerable to earthquakes and flooding. They are also more expensive to build and maintain. By comparison, it costs approximately 3-5x more per foot to construct underground power lines versus overhead lines. Furthermore, it would cost in excess of $600 million to bury the remaining overhead lines in our service territory. In order to avoid passing that cost onto our members, we continue to apply for FEMA grants to underground more of our system each year.

Pros:

• Protected from wind, wildfire, weather, tree branches and damage from most animals.
• Less susceptible to outages from vehicles colliding with poles.
• Reduced risk of electrocution from downed lines.
• Aesthetically more pleasing, with poles and wires out of sight.

Cons:

• More expensive to build and maintain.
• Time consuming and expensive to locate and repair a malfunction.
• Vulnerable to damage and electrocution from digging or other construction.
• Susceptible to damage from earthquakes and flooding of the transformer box.
• Not practical in unstable sandy or rocky mountainous areas.
• Ultimately fed by overhead lines.

What is Lane Electric doing?

Trees are the number one cause of outages in our rural service territory. Our tree-trimming program is staffed with arborists and forestry experts who work tirelessly to keep our members safe and reduce the chance of power outages. Our tree crews are constantly trimming and removing trees under power lines in our ongoing effort to make your electric service as reliable as possible. In addition to tree trimming, our crews perform regular equipment maintenance and take planned outages as necessary to repair or replace equipment.

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Additionally, we are actively applying for FEMA grants to move as much of our system underground as is feasible and mitigate the extreme weather risks above-ground power lines are susceptible to. We are committed to doing so as effectively as possible and at no-cost to our members.

What can you do?

There are two methods of installing the power lines that carry electricity to your home, overhead and underground. San Patricio Electric Cooperative members sometimes ask why we use one versus the other, or more to the point, why all power lines are not installed using the underground construction method. Isn’t one method better than the other? These are great questions, and the answer is that each method has its place.

Let’s take a look at some the advantages and disadvantages of each construction method, beginning with overhead.

Overhead construction

Overhead line construction starts with the setting of utility poles. Poles can be set in nearly any type of terrain, even rocky. In the case of heavy rock, special equipment is used to augur out the hole. If placement occurs in boggy or wet terrain, many techniques are available to set poles securely. Once the poles are in place, wires can be strung and then equipment––like transformers, fuses and reclosers­––are installed.

Pros:

• Lower cost. Overhead power lines are a less expensive way to get power to your home. They are also less expensive to repair and upgrade.
• Quicker construction. Overhead lines can be installed relatively quickly, since there’s no need to trench.
• Easier to spot damage and faults. Our linemen can see the entire line when its placed overhead, which makes it easier to spot outage causes or potential problem areas.
• Can be built anywhere.
• Any voltage can be placed overhead.

Cons:

• More susceptible to bad weather, such as high winds.
• More vulnerable to damage from trees and vegetation, which requires right of way trimming.
• Vulnerable to blinks when animals and branches contact lines.
• Susceptible to damage from vehicle collisions.
• Less attractive.

Underground construction

Underground line construction requires digging a trench that is deep enough to keep the lines well away from surface activities. Where the terrain is extremely rocky, underground lines may not be an option. Next, wires are laid in the trench directly or placed in conduits for protection. The trench is filled in, and the surface is restored to its original condition. Padmount transformers and additional equipment are installed as needed.

Pros:

• Not vulnerable to damage from tree branches; no right of way trimming required.
• Less susceptible to damage from vehicle collisions
• Not impacted by wind
• Less vulnerable to blinks when animals and branches contact lines.
• More attractive. Some people choose to install underground power lines so the infrastructure doesn’t obstruct their view.

Cons:

• More expensive to build and repair
• Fed by overhead lines. At some point, all underground power lines are connected to overhead lines, which makes them vulnerable to outages.
• Susceptible to flooding
• Difficult to locate faults
• Limitations on voltages that can be buried underground.
• Can be vulnerable to dig-ins. Make sure you always call 811 to locate underground utilities before you dig.

Determining if power lines should be overhead or underground boils down to what is best for the situation. Underground lines might be ideal in situations where there is a desire to keep the poles and wires out of sight, such as a residential neighborhood, park or historical area. There are many cities and towns that construct only underground lines for a variety of reasons.

Overhead systems work well when appearance is not a major concern. Examples include extremely long line distances across country, and where the voltages are higher than the limitations set for underground lines.

The company is the world’s best Overhead Line supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.