It was a calm November morning when the power cut out to sizable share of Marshall, Minnesota for 13 minutes.
The culprit wasn’t a fallen tree, a gust of wind or an inconsiderate neighbor forgetting to call before digging a hole in the backyard.
It was a much smaller menace: a squirrel.
To most power customers, the question of consequence in the midst of a power outage is when the lights, the refrigerator and the TV will be back on. Not what caused the outage.
But lots of the time, the answer to that question is squirrels.
These wily rodents cause so many power outages that they pose a greater threat to the electrical grid than natural disasters and cyberattacks, said former deputy director of the National Security Administration John C. Inglis. “I don’t think paralysis [of the electrical grid] is more likely by cyberattack than by natural disaster,” he said, per Engadget. “And frankly the number-one threat experienced to date by the U.S. electrical grid is squirrels.”
Scourge on a wire
Minnesota, home to plenty of squirrels, is no exception. “I’ve been working here 20 years and probably the largest (outage) we’ve experienced was caused by a squirrel that got into our main substation right downtown here,” said Scott Mellenthin, purchasing and property coordinator at Marshall Municipal Utilities.
The substation was well squirrel-proofed, except maybe one spot. “We thought, not in a hundred years would that squirrel get there and he did,” Mellenthin said. “The entire building went black and part of town went black.”
Luckily, he said, squirrel-induced outages tend to be quick fixes.
According to the American Public Power Association, which serves community-owned utilities, squirrels caused 3,456 power outages at municipal utilities in 2016, cutting power to nearly 200,000 customers. Squirrel-related outages are most common in the Midwest and the northwest, said Mike Hyland, the American Public Power Associations’ senior vice president of engineering services.
“There’s all sorts of trees in Minnesota, and that means lots of squirrels,” said John Muehlbauer, the superintendent of line operations at Minnesota Power, in Duluth.
A spokesman for Xcel Energy, which serves the Twin Cities and much of greater Minnesota, said the company doesn’t track squirrel-related outages specifically, but noted it is a cause from time to time.
There’s a reason squirrels are the culprit behind so many power outages: the dexterous animals use power lines to move among trees, where they find food and shelter. “I think it’s just their athletic ability,” Mellenthin said. “They love to use overhead lines for accessibility to things. It gets them closer to the things they want to be close to, their food source and cover, that type of thing.”
When something — human, object or animal — touches two of those lines at the same time, or otherwise creates a connection and completes a circuit, said conduit is likely to blow a fuse and burn to a crisp in the process.
“They jump onto our line and as long as they’re on that one line, they’re fine,” Minnesota Power’s Muehlbauer said. “It’s when they touch something else that they tend to complete a circuit or create a fault, which kills them and creates an outage for us.”
Squirrels are not the only animals that tend to disrupt the electrical grid, Hyland said. In South Florida, it’s iguanas, who like to climb power poles to sun themselves. In Guam, it’s snakes, which like to coil out onto power lines. Birds are sometimes to blame, too.
There are things that can be done to squirrel-proof power grids — at least to some degree. Utilities install plastic squirrel guards around equipment and wires to try to save the rodents from themselves.
But squirrels teeth never stop growing. And their predisposition to gnaw in order to grind those teeth down means they like to chew on the very things designed to protect them.
Minnesota Power has installed what are called trip savers, which detect a temporary issue — like a squirrel on a line — and flash the power off quickly, so the squirrel can fall off the line before a fuse breaks, Muehlbauer said.
In Marshall, the utility company has moved some power lines underground, which makes gophers a bigger threat. But they don’t come close to squirrels in terms of the number of outages caused.
All told, Marshall has cut the share of squirrel outages down from about 12 percent of incidents to 4 percent, Mellenthin said.
It’s tough to stop the critters from interfering, though, says Mellenthin: “They’re amazing animals.”