Burying Power Lines

Burying power lines (also called “undergrounding” by engineers) seems like an obvious way to improve reliability. Those of us in the industry are used to seeing interest in this idea surge at the local and state level every winter, with another bump sometimes after hurricane season! An honest study of the costs and benefits, however, reveals a more complex picture, one in which the true value of undergrounding is highly dependent on local conditions.

The assumption by most people is that burying power lines will reduce the amount of time they spend without power. And it’s true that buried lines are less likely to experience outages, though it’s probably not as much an advantage as people think. Underground lines can be affected by flooding, digging, corrosion, and tree roots. When a line is underground, it’s also much more difficult to locate and isolate a problem. Thus when there are problems with buried power lines, the lines tend to remain out-of-service for longer.

Speaking of problems, let’s address maintenance, where again the story is not so simple. Getting to underground lines requires more time, bigger crews, and heavier equipment. On the other hand, compared to overhead lines, vegetation management is a lot simpler and can be performed at significantly reduced cost. Buried lines also avoid clearance issues in commercial areas.

Construction of new underground lines is a lot more expensive than putting up overhead lines for similar reasons to the cost of maintenance. [See the video below for a walk-through of the underground construction process.]

Other significant factors affecting the cost-benefit calculation include aesthetics and safety, both of which typically support undergrounding. Simply put, people don’t like looking at poles and lines in their neighborhoods. Exactly how much of an affect there is would be difficult to say, but the analysis usually assumes that overhead lines negatively impact property values. Safety is a factor mostly because of the poles. Tens of thousands of accidents and a significant percentage of vehicle fatalities involve utility poles.

Yes, it would be nice to have those lines and poles out of the way. The question is, are we willing to pay the price?

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