X-ray Vision

New Scanning Technology Helps Monitor Transmission Lines

On an ordinary day at TVA’s lineworker training facility, you might see apprentices learning to climb with gaffes strapped to their legs, playing catch with a basketball while perched high in a forest of 50-foot wooden power poles.

But this isn’t an ordinary day at the Bellefonte site in northeast Alabama.

And no apprentices are present.

Just seasoned TVA experts who’ve become trainees for a day.

They’re sheltering from the stifling heat and humidity under a covered pavilion, dodging the occasional wasp.

There’s a lot on the line, so to speak: 16,000-plus miles of electricity-conducting cable and more than 104,000 towers and poles.

With that much transmission infrastructure, how does TVA continuously improve reliability and safety?

Today’s training advances that mission with a new X-ray device that lets TVA better inspect its transmission lines to determine which need maintenance attention, or even replacement.

But first, TVA’s lineworkers and its radiography team must learn to operate the new technology.

From left, transmission maintenance foreman John Garner and lineworkers Phillip Walker and Ryan Anderson ground the bucket truck.

Broken Splice

“Fire in the hole,” radiography specialist Todd Kirk calls out.

About a dozen people shuffle backward, a safe distance from the X-ray machine.

The oddly shaped device, about the size of a fireplace grate, emits a brief tone.

Then the group surges forward, clustering around Kirk’s laptop to view an image like what you might see at the emergency room if you broke your arm.

Except the broken part is a transmission line splice.

Joe Turk, TVA’s senior program manager for transmission lines, points to a slight gap appearing in the sample the team has just X-rayed.

“The grip is separated from the core,” he says.

With the integrity of the steel core compromised, there would be only an aluminum casing bearing a load of 9,000 to 15,000 pounds.

That type of flaw in a splice could cause a transmission line to fail, producing an outage or even a hazardous situation.

This new alliance of radiographers and lineworkers is determined to prevent that from happening.

The team studying transmission X-rays includes, foreground from left, radiography specialist Todd Kirk, senior program manager for transmission lines Joe Turk and Garner; rear from left, transmission system maintenance specialist Jason Hunt, transmission general foreman Micah Livingston and senior program manager for transmission asset strategy Tyler Daniel.

Preventive Maintenance

The X-ray training is part of an ambitious campaign to strengthen preventive maintenance of TVA’s transmission system, which delivers electricity to 153 local power companies and 61 industrial customers in seven states.

“We want to be proactive, not reactive,” Turk said. “We want to replace the thing the day before, or the year before, it breaks.”

This effort builds on the work of TVA’s 26 line crews, each one responsible for inspections and maintenance over a territory spanning hundreds of miles of line and thousands of structures.

“Each of those crews knows their area inside and out,” Turk said. “If I call a foreman and say, ‘I need to get to Structure 10 on Line XYZ,’ he tells me, ‘Alright, you go down here, you turn at the red barn, you cross three gates and you're there. And watch out for that bull over in that pasture – it’s mean.’”

The idea is to equip line crews with tools that can serve as early warning systems.

For instance, research shows nearly half of transmission line failures are due to joints breaking down, Turk said – but any internal weaknesses are invisible to the naked eye.

The new X-ray technology can identify those problems before they get big.

It lets crews in the field make a more accurate assessment of what they’re dealing with and how best to proceed, said Jason Hunt, TVA’s transmission system maintenance specialist, who advises crews on tricky cases.

“This is one of the tools in our tool bag,” Hunt said. “You’re going to look at the very inside of a joint and see exactly – does it still have the proper amount of filler? Was it properly installed? Has the interior core degraded over time?”

X-ray images like this allow crews to examine the steel core and other features invisible to the naked eye.

Enhancing Infrared Scans

Line crews patrol annually on foot and by helicopter. Once every four or five years, they also do complete infrared scans, which detect overheating.

“Infrared only shows you there's a problem when it's a really bad problem,” Turk said. “What we're doing with the X-ray technology and some of the other scanning technologies is trying to get ahead of that and understand how the age and the environment and construction methods affect longevity.”

Alongside the splice X-rays, the preventive maintenance campaign is incorporating:

• Drones that can provide close-up photos of components crews can’t see well from the ground.
• A robot that rides along lines, scanning for signs of corrosion of the steel core.
• Soil sampling and corrosion mapping programs to prevent below-ground damage to steel structures.

Daniel shows a dead-end fitting, like the one in the X-ray above, which is used to attach a transmission wire to a tower or pole.

‘Pennies Today'

If a creek floods in the middle of the night and washes out a transmission tower, Tyler Daniel is the guy who gets called to look up specs for an emergency repair.

As you might expect, Daniel is a big believer in preventive maintenance – and not just because it lets him sleep through the night.

“Preventive maintenance is way cheaper than emergency maintenance,” Daniel, senior program manager for transmission asset strategy, said. “It’s pennies today, dollars tomorrow.”

TVA’s maintenance culture is built on the understanding that preventing small problems from escalating keeps the power on for the people of the Valley region.

Daniel gives the example of insulators, the glass or porcelain components that keep electricity away from towers and poles. A cracked insulator may still function, but once it actually breaks and fails, circuit breakers will trip the line off, causing an outage.

“We go through and inspect those,” Daniel said. “If we can change them out before that happens, we’ll prevent an outage.”

Turk and his team will use the X-ray data to help make important decisions such as when aging conductor wire needs to be replaced.

Setting Priorities

The preventive maintenance program also helps prioritize which infrastructure to replace.

Conductor – the actual wire that transmits electricity – is expected to last between 75 and 100 years, Turk said.

By that math, TVA has more than 3,200 miles of transmission line nearing the end of its life expectancy.

“We're looking at major investments in asset replacement over the next 10 to 12 years,” Turk said. “Our modeling is trying to figure out what projects are more important than others. Everything can’t be Priority 1.”

The data accumulated from X-ray scans and other preventive tools will help Turk’s team identify trends about TVA’s equipment.

That data goes into the mix with other factors, such as the age, location, load and history of the line, as well as reports from line crews who know the infrastructure most intimately.

Safety is the most important issue.

Lines that cross rivers, roads, railroads and parking lots are always closely scrutinized, Turk said.

“The public safety component of what we do is something we take very, very seriously,” he said.

Hunt readies a grounding cable that makes it safer for the crew to work on transmission lines.

Wise Investment

TVA is not alone.

Electric utilities around the country are developing best practices for maintaining and replacing older infrastructure, Hunt said.

“We all have aging assets, and one of the big pictures in having a readily available supply of electricity is keeping current assets up and running,” he said. “To do that, we've got to have a lot of maintenance – and not just any maintenance, but the right type of maintenance.

“That’s what I’m here for, to figure out exactly what is the right type of maintenance going forward."

At day’s end, investing in maintenance is the same smart choice most car owners make, Turk said.

“You could choose not to change your oil,” he said. “That’s fine, but eventually it’s going to cause a reliability problem.”

Photo Gallery

Garner straps on a safety harness before going up in the bucket.

Walker sets up the X-ray device to make images of a splice.

These samples give lineworkers and radiography experts practice using the new X-ray technology.

The crew removes the ground rod after completing X-ray scans.

Kirk and others inspect an X-ray image.

At TVA’s lineworker training facility at the Bellefonte site in northeast Alabama, this table of parts helps apprentices learn to identify transmission line hardware.

PHOTO AT TOP OF PAGE: Walker positions the new X-ray device on a transmission line for training.