Few things are more disruptive and frustrating than the power going out.
While storms and vegetation are leading causes of power outages, Duke Energy responds to a variety of other outage causes as well, requiring crews to be ready at any time – in every type of weather – to repair equipment and get power restored for customers.
So couldn’t power outages be prevented altogether by putting all lines underground? The short answer is no, said Duke Energy spokesperson Jeff Brooks.
For one thing, while underground lines may be more resistant to weather-related outages than overhead lines, they are not immune to outages. Common causes of outages on underground lines include equipment dig-ins to cables, water intrusion and even rodent damage. And underground line repairs can take much longer than overhead lines, which are easier to access.
Then there’s the cost: Converting existing overhead power lines to underground lines can be expensive and may involve tree removals and new easement acquisitions to complete. And that translates to increased costs for customers.
A more holistic approach to reliability
Duke Energy does underground some power lines, with about one-third of the company’s 300,000 miles of power lines located underground. New developments often elect to place power lines underground, an extra cost typically paid for by the developer. And in some instances, burying sections of outage-prone overhead lines has proved to be an effective solution for reliability concerns.
Improvements can include pole and power line upgrades, vegetation management, capacity improvements, and wood to steel pole conversions, as well as flood protections and the installation of smart, self-healing technology.
Self-healing technology can automatically detect a power outage and quickly reroute power to other lines to isolate problems and restore service faster – often in less than a minute.
More than 55% of Duke Energy customers are served by self-healing and automated restoration capabilities. That represents a nearly 65% increase in customers served by these technologies over the last two years.
“About 80% of our self-healing customer benefits across the enterprise so far in 2024 were gained during severe storms,” Brooks said. “There may still be damage for crews to repair, but it also means far fewer customers may be impacted by an outage. And that means getting life back to normal faster when our customers count on us most.”
This technology is also fundamental to expanding cleaner energy, like private rooftop solar, electric vehicles and battery storage.
“The same multidirectional power flow that this system enables to restore power faster is what we need to support innovative power solutions across our service areas,” Brooks said.
Burying all power lines would lead to higher electric bills
When Duke Energy does need to bury a power line for reliability reasons, it is based on the analysis of high-resolution data that looks at the performance as far down as individual spans of power lines between two poles.
This data allows crews to place sections of outage-prone line underground while leaving the rest of the line overhead – saving customers money while still delivering improvements.
Burying thousands of miles of lines would increase costs exponentially – and may not even be feasible in some areas. Take the North Carolina mountains: Cutting through rock in this area to bury lines would cost about 10 times as much as elsewhere in the state, and would require tree removal to place lines where tree roots are today.
Widespread replacement of overhead power lines would increase monthly electric bills by more than double and take at least 25 years to accomplish in North Carolina, according to a study by the state’s utilities commission.
“Such an undertaking would be cost-prohibitive,” Brooks said, “and not deliver enough reliability improvement to justify that significant expense.”
Finding solutions to improve reliability
In the end, there is no single failsafe approach to preventing outages. After all, power lines under ground cannot exist independently; they are connected to substations, which operate above ground, and overhead transmission lines, which supply power across entire regions to Duke Energy’s 8.4 million customers in six states. Instead, for Duke Energy, it’s a case of the right tool for the right job.
“People tend to imagine that placing all lines underground is a panacea for all reliability problems,” Brooks said. “But there’s a right solution for every location.”
