ITC Holdings is used to severe weather, with a 16,000-mile transmission network that faces harsh winters in Minnesota and tornadoes in Oklahoma.

But the derecho that hit ITC’s operations in Iowa on Aug. 10 was a new kind of challenge, forcing the company to seek mutual aid for the first time in its nearly two-decade history, Director of Real-Time Operations Darrel Yohnk told NERC’s eighth annual Monitoring and Situational Awareness Technical Conference on Tuesday.

A derecho packs wind speeds equal to a Level 2 hurricane, but the winds blow in straight lines rather than circling. They can occur in a band of rapidly moving thunderstorms when rain-cooled downbursts reach Earth’s surface and spread horizontally.

“A lot of thunderstorms have [downbursts],” Yohnk explained. “What makes a downburst a derecho is the fact that these downbursts can be self-propagating, and they suck more dry air into the storm, making the winds even stronger.”

The National Weather Service defines a derecho as wind gusts of at least 58 mph that cause a swath of damage of at least 240 miles, “which is just huge,” Yohnk said.

The National Oceanic and Atmospheric Administration said the August storm was the most costly thunderstorm disaster in U.S. history, causing four deaths and an estimated $7.5 billion in damages over a 700-mile path from Iowa to Indiana.

The storm, which carried wind gusts exceeding 100 mph, knocked out more than 1,200 miles of transmission on 144 lines, nearly 20% of ITC’s Midwest network. Almost 800 workers were brought in from other companies to help replace more than 1,000 wooden and steel poles.

The nuclear-fueled Duane Arnold Energy Center near Cedar Rapids, Iowa, lost off-site power for almost a day. The plant got its emergency on-site power running just 11 minutes before losing off-site power, after the loss of four 161-kV, one 115-kV and two 69-kV lines, Yohnk said.

The system “got weak enough that when the [345-kV] Duane Arnold-Hazleton line tripped, the impedance changes on the system were massive. We experienced a power swing event, with the Duane Arnold area swinging against the rest of the [Eastern] Interconnection.”

During the swing, zone 1 relay settings caused the tripping of a 161-kV and two 69-kV lines which created an electrical island of the nuclear plant and some load out of Hiawatha, Iowa. “A few seconds later, the island breaks up further and the remaining [345-kV] Duane Arnold-Hiawatha line tripped and that isolated the plant by itself,” Yohnk said.

The 161-kV Duane Arnold-Hiawatha line exceeded its system operating limit, with flows 9.5% above the short-term emergency rating for 1.4 minutes. “Of course, we were implementing our operating plan to address that. The plant was ramping down as fast as it could, but this storm activity was impacting us faster than … we could get the unit ramped down,” Yohnk said.

ITC, a unit of Fortis, lost more than 900 MW load, with 500,000 customers — 30% of its Iowa customer base — losing power.

The last customers were energized at midday Aug. 18 after eight days, “which was a phenomenal feat for us,” Yohnk said.

Operating During Pandemic

Yohnk and officials from American Electric Power and Florida Power & Light also shared with the conference their experiences in running their grid operations during the coronavirus pandemic.

ITC’s operations control room (OCR) is located in Novi, Mich., 30 miles from Detroit, which in March was one of three COVID-19 hotspots in the U.S., along with New York City and New Orleans.

ITC had a “fairly generic” pandemic plan, Yohnk said. The plan had been “pretty much theoretical because we really haven’t had opportunities to implement it, fortunately, over the years, unlike our transmission system response plan,” which was activated during the derecho.

ITC removed its operations planning and relay performance engineers from the control room and issued a work-from-home order March 16 while soliciting volunteers for sequestration.

It created three “waves” of staffers to provide day/night coverage for the OCR and two groups for the physical security command center, with one group sequestered on-site and the others sequestered at home. ITC contracted for all three floors of a hotel adjacent to its headquarters to house the workers.

The OCR staff worked 14 consecutive 12-hour day or night shifts before being replaced. Operators tried to avoid using the same consoles in consecutive shifts.

Other staff provided “daily life assistance” to the sequestered workers, such as delivering groceries and medical supplies, and caring for pets.

The company also sanitized its backup control center — a facility 35 miles from its primary control center that is normally used for training — in case it was needed.

Being sequestered increased the camaraderie of the groups, Yohnk said. “A lot of times in their normal day to day … they get focused on their own work activities and they don’t interact as much on a personal level. The sequestration did give them the opportunity to do that on a much more frequent basis.”

Phil Hoffer, the manager of emergency management system applications at AEP Transmission, said the company did not implement sequestration but that 13,000 of its 17,000 employees began working from home and will probably do so until at least summer 2021.

Hoffer said workers used levity — sharing favorite pandemic songs and goofy high school pictures of themselves — to keep their spirits up. “I think that really helped our employees and supervisors with the stress they were experiencing as a result of all the changes,” he said.

“For the most part, we’ve actually been more productive out of the office than we were in the office” because of fewer interruptions, Hoffer said. “Now, my group’s a little different because only one of the people on our team has school-age kids at home. I think your ability to get things done would change dramatically if you had three or four or five school-age kids at home.”

Hoffer said the company uses video of all its attendees for its remote meetings. “I think it’s easier to pay attention if you’re on camera,” he said. “We’re trying to find ways to make it more like we’re in a meeting, where you kind of have to pay attention.”

Rob Adams, FPL’s senior director of grid control systems for power delivery, briefed the conference on the tools the utility deployed to stay connected, including Microsoft Teams to facilitate remote communication and collaboration.

FPL also used Klaxoon, an app that helps managers keep staff engaged during remote meetings by allowing them to answer questions via their cellphones. “They enjoyed the idea of reacting to the presentations,” he said.