CHARLOTTE — If you lose power after a strong summer storm blows through the area, you’re probably wondering when it’ll come back on and what can be done to keep it on.
According to Duke Energy, falling trees and branches are the No. 1 cause of storm-related outages, so it stands to reason why many want to know why the utility doesn’t move the power lines underground and out of the way.
Research shows undergrounding does help. According to a report from the Department of Energy, a 10% increase in underground lines in any given utility system means on average, a 14% decrease in annual outages.
Robert Cox, the executive director of the Energy Production and Infrastructure Center at UNC Charlotte, explains the biggest barrier nationwide is cost.
“Undergrounding in and of itself is a pretty expensive proposition,” he said. “[Regulated utilities] have to make the most prudent financial decision based on the risk that they face.”
The risks are highest in northern climates that deal with more icing concerns, but Cox said in places, such as the Carolinas, other less expensive resiliency interventions often win out.
Duke Energy spokesperson Jeff Brooks said the work could involve tree trimming, upgrading power lines and utility poles, possibly making them taller, and installing “self-healing” grid technology.
“That technology can automatically reroute power around a problem to restore service faster when an outage occurs,” he said.
North Carolina studied the potential benefit of undergrounding in 2003 after an ice storm in 2002 knocked out power to more than half of Duke Energy customers in North and South Carolina.
In their findings, the study found undergrounding the entire existing system would roughly halve the number of expected outages but the process would take 25 years and more than double customer power bills.
Additionally, while undergrounding does improve reliability, Cox said it’s not full proof. Outages do occur on underground systems, especially due to water getting into the system.
“Those outages are going to be a lot longer, typically because it’s harder to replace it,” he said.
Depending on where those lines are buried, fixing them could mean digging up roads or sidewalks and working around other infrastructure, including fiber and gas lines. Brooks explains that’s also why retroactively undergrounding lines tends to be so expensive and time-consuming.
“We often have to get new easements to be able to move that line to another area where we can place it underground,” he said. “We often have to remove lots of trees to create a path for that line to be placed underground and then you have to place it with other things that are down there like fiber optics and natural gas lines.”
In some cases, Duke Energy will approve undergrounding projects, particularly if an area sees a disproportionate number of outages and adding additional resiliency measures are unfeasible.
Otherwise, Brooks said areas that have underground lines typically started with those lines underground in the first the place.
“In new developments, we place lines underground working with developers,” he said. “They pay the difference between the overhead line and the underground line. But because it’s new construction, it’s much less intrusive, much easier to place that line underground than in an established neighborhood.”
Currently, about one-third of Duke Energy’s 300,000 miles of power lines are underground and if you happen to be in a neighborhood with underground feeding, you’ll likely notice a difference.
“In my neighborhood, one side of the street, we have underground lines and across the street they don’t,” Cox said. “They have a lot more outages on the side with overheads than we do, but when we have outages, they’re a lot longer.”
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