A Virginia Tech-based research team plans to spend three years studying how to make drilling underground to bury power lines safer and more cost-effective, with a goal of helping to improve the resiliency of the electric grid.
Backed by a recent $2.5 million U.S. Department of Energy grant, the researchers plan to develop a system using sensors and artificial intelligence to give drill operators a picture of what’s ahead as they bore through the ground.
Among the team’s aspirations is being able to detect water lines, sewer mains, boulders and other underground obstacles up to 10 feet in front of the drill, said Joe Vantassel, assistant professor in Virginia Tech’s department of civil and environmental engineering and the principal investigator for the project.
“What we’re going to exactly be able to achieve is an open question of research. … We’re definitely going to push it as much as we can,” Vantassel said.
Benefits and risks of underground power lines
Most electric power lines are strung overhead from one wooden or metal pole to the next. That’s cheaper than running lines underground, but it also means those lines are vulnerable to heavy winds, snowstorms and other damaging events.
Appalachian Power cited the cost of repairing storm-related damage as one of the chief reasons it’s asking state regulators to approve a rate hike that would increase the average residential bill by $10 a month for its 540,000 customers in western Virginia.
There are essentially two ways to bury power lines: dig a trench and bury the line, or drill under the ground and run the line through the tunnel. Vantassel’s team’s research focuses on drilling.
Underground drilling comes with risks. Drill operators might hit a natural gas line, a water line or a big rock that the drilling crew didn’t know was there. That can cause safety issues and delay work.
Digging a trench and placing power lines in it is typically one to two times more expensive than stringing wires overhead, and burying wires via drilling can be three to four times more expensive, said Appalachian Power spokesperson Teresa Hamilton Hall.
The Virginia Tech team isn’t working with Appalachian on its research, but Vantassel said the team would eventually like to explore whether the state’s second-largest utility would be interested in the project.
“Challenges include uneven terrain, rock and rocky soil,” Hall said of underground drilling. “Flood plains are an issue. Some areas are adjacent to rivers and creek beds, which makes undergrounding difficult. Other challenges include right of way. In cities, you have to navigate around other utilities.”
Appalachian maintains more than 5,000 miles of underground lines in Virginia out of a total of 31,500 miles of distribution wire, Hall said.
In situations where the utility is going to bury power lines, it digs trenches, typically about 3 feet deep, whenever possible. But it does use drilling — also called directional boring — in some cases, such as crossing roadways. Hall pointed to Virginia 419 in Roanoke County, aka Electric Road, as one example.
The company has two electricity networks that are entirely underground: in downtown Roanoke and in downtown Lynchburg. All of the equipment — cables, transformers, switches and so forth — is underground, Hall said.
Hall said one misconception about underground power lines is that there is zero chance of the power going out.
“That’s not the case,” she said. “Equipment still ages and fails, and an issue could occur along a circuit prior to the point where the line goes underground. When there’s an outage underground you can’t see where the problem is — or what the problem is — so it will often take longer to dig up, locate, and the splicing to make a repair underground generally takes longer because the work to splice is more detailed and takes longer.”
Making waves, detecting hazards
With those benefits and risks in mind, the Virginia Tech team is looking for a high-tech solution to help.
At the core of the plan is the fact that as a drill bores through dirt and rocks, it creates vibrations, or seismic waves.
The team plans to use those waves to sense obstacles in the drill’s path.
“You can think of, if you tap on a table, if you have a friend on the other end of the table, they can feel that tap,” Vantassel said. “And those are actual waves that are traveling through the table. And in a similar way, we can sense what’s going on around the drill head by listening to the vibration that that drill is putting into the ground.”
Other sensors around the work site would detect other vibrations — for example, from cars driving nearby.
“So you’d have a sensor that’s not at the drill,” Vantassel said, “and it would pick up something, and then the technology would be able to process that in a way that says, OK, well, I know that this is another source separate from what we’re seeing underground.”
Those sensors would be combined with ground-penetrating radar, and all of that data would be tied together and processed with artificial intelligence to provide the drill operator with predictions about what’s ahead in the drill’s path, Vantassel said.
“We’re really excited about this project and the potential that it could have to allow us to put power lines from above over our heads to bring them underground and ultimately to make the electrical grid so much more resilient and to allow us to keep the power on, regardless of large weather events and other things,” Vantassel said.
Looking ahead
The Virginia Tech project is set to kick off in August. The federal grant will pay students working the project and cover hardware expenses as the team works to build a lab-scale prototype.
The research team includes other professors and scientists from Virginia Tech as well as professors from the Colorado School of Mines and Brigham Young University.
The researchers are collaborating with the Virginia Tech Electric Service, which powers the Blacksburg campus, where most power lines are underground. Vantassel said the electric service has helped inform the team about what some of its challenges are and what it sees on a day-to-day basis as a utility that runs power lines underground.
If successful, the team’s work could have applications beyond burying lines.
“This idea of — at a very basic level, of course — of digging underground and being able to sense what’s ahead and using that array of sensors … that could potentially go into areas of mining, construction, things like that,” Vantassel said.