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United Cooperative Services News

Blink, Blink, Blink

Occasional power blinks often indicate circuit reclosers prevented a permanent outage

Spring and summer storms or sometimes even just the wind can cause momentary interruptions in member electricity delivery called blinks.

While United Cooperative Services always wants to hear from members when the power goes out, it’s often best to wait a few minutes before contacting the co-op, said Jared Wennermark, the vice president of Planning & Procuring.

“There are devices on our system called reclosers that are designed to open and close circuits several times before they stay open (an open circuit means the current cannot flow from one end of the power sources to the other),” Wennermark said. “Think about breakers in your home. When they trip, they stay tripped until you flip them back on. These reclosers will open and close a circuit up to four times with the purpose of clearing a temporary fault and avoiding a permanent outage.

“The main thing we want members to know is that when they see occasional blinks, a permanent outage was avoided. They can understand that the system is working the way it’s designed to work. The technology has prevented members from experiencing a permanent outage that could take up to two hours to fix. While we strive to avoid any interruption, occasional blinks are much more preferable than a sustained outage.”

When debris, such as a tree limb, falls across the lines, reclosers will trip off the electricity to test whether the obstruction was temporary, Wennermark said. For the vast majority of incidents, this prevents members from experiencing a permanent outage in which lineman are dispatched to make sure lines are cleared before restoring power.

On a clear day, the trips are set to open four times slowly since contact with the lines is unexpected. During a storm, though, the trips open more quickly to prevent damage from lightning strikes.

“The normal routine is up to three open intervals from a few seconds to up to 15 on a clear day, and in stormy weather, the intervals last only a few seconds. That’s controlled by programming in the recloser itself,” Wennermark said.

“United has the technology to remotely change from a clear day setting to a rainy-day storm setting. The reasoning behind a slower response and longer open intervals, allows more time for obstructions such as swaying tree limbs to clear the line,” he added.

Recently, United began emphasizing blink-pattern analysis. By plotting all the blink data collected from advanced metering technology, engineers are able to identify patterns that dispatchers might not observe in real-time. By plotting all the blinks over time, clusters of problem areas may emerge, tipping engineers off that a certain area may need more tree maintenance to prevent blinking or even future permanent outages that will take time and man-hours to correct.

United engineers also are looking at other ways to minimize blinks and outages caused by trees and vegetation contacting the lines, Wennermark said. The majority of blink issues usually come from this problem.

The last two seasons have seen more rain, which has caused a surge of new growth on area trees, Wennermark said.

“Naturally, we’re seeing a lot more growth compared to past drought years, and that growth creeped up to the extent that, now, when you have a storm situation and the wind blows you have some of that new growth contacting that line. Or, you can have limbs pushing wires against each other when the wind blows. So now, the question is what are you going to do about trees?”

United plans to launch a more strategic vegetation management effort to remediate tree growth in areas where the contact problems are most persistent. Members in these areas will be contacted about upcoming right-of-way work throughout the system.