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Bird’s-eye view of OPPD’s transmission system

Last week, OPPD personnel wrapped up yearly aerial transmission inspections of the utility’s system. Each fall, OPPD contracts a helicopter to take line maintenance technicians up so they can get a unique and comprehensive view of the transmission system.

The OPPD system spans from South Sioux City, Iowa, to the north, to the Missouri border to the south. In all, they fly about 1,000 miles over five days.

“We always try to focus on all our rural 345-kilovolt (kV) and 161-kV lines,” said Gary Wohlman, an OPPD line technician and veteran of many flights. “Most of those are in pretty rugged terrain, so it makes it more efficient using the helicopter. We can cover a lot of land in a week’s time.”

Wohlman said the lower the voltage of the lines, the more difficult they are to fly and inspect. Structures on lower voltage lines are shorter, which makes it more hazardous. He said they do fly some of the lines on the outskirts of Omaha and Lincoln.

Weather factor

The flights have proven to be the quickest and most economical method to spot potential problems in OPPD’s transmission system.

A helicopter contractor pilots the aircraft. The duration and path of inspections depend on the weather. Wohlman said it is best to fly into the wind. They fly about 35 mph and come within about 25 or 30 feet of the lines. State and local law enforcement agencies are notified and updated of the flight path and timelines.

Wohlman said since he was unfamiliar with the pilot in last week’s flight, they flew the 345-kV lines first since they have more limited hazards.

“That way we can get used to each other, the language and terminology we use,” he said. “It’s kind of like going with a new driver, you’re going to go on country roads or parking lots.”

Flying with two

Inspectors generally find a few issues that require quick attention to ensure the system’s reliability. When they do, OPPD dispatchers and T&D Operations personnel are notified so they can arrange for planned outages, crews, material and equipment needed to make repairs.

“Some years you find more damage than others,” Wohlman said. “There’s no rhyme or reason to it, but you are pretty sure you are going to find something.”

And they always fly with two line technicians. The one in front, typically Wohlman, does the inspections, while the one in the back of the helicopter looks out for potential hazards.

In addition to the condition of transmission lines and structures, inspectors check the clearance around the lines. Trees, sheds and other objects placed too close can cause service disruptions.

The flights are a valuable tool for the utility to keep the system healthy and reliability high.