By Eric Barendsen 

When frigid temperatures cascaded south across the country in February, demand for electric power surged and generation faltered. Electric grids from Montana to Texas buckled under the strain. The Southwest Power Pool had to roll blackouts throughout its 14-state power grid to avert a disastrous, long-term outage. 

While 21 WAPA customers experienced approximately one-hour outages over the course of two days, WAPA and the Army Corps of Engineers worked together to step up hydropower production and help stabilize the grid.

WAPA also flexed its financial reserve strategy and purchased power on the spot market to make its contractually guaranteed deliveries. These critical measures and other takeaways will inform WAPA’s response to future grid challenges.

The cold reality

Driven by a polar vortex, severe winter weather arrived mid-February, delivering record-setting low temperatures in the Midwest and a snow and ice storm all the way down to the Gulf Coast. Arctic air plunged into Texas, which reported some of its coldest temperatures on record, including two degrees below zero in Dallas.

Residents and businesses across the region dialed up their thermostats, causing a spike in electricity demand. At the same time, the bitter cold sidelined a number of powerplants—including both traditional and renewable resources—which reduced available electricity.

Shock to the system

Upper Great Plains is part of a group of transmission operators managed by the Southwest Power Pool. One of 13 reliability coordinators in the Eastern Interconnection, SPP’s grid covers a 14-state footprint from Montana to Minnesota in the north, reaching into Arkansas, New Mexico, Oklahoma and the Texas Panhandle in the south. 

SPP is WAPA’s reliability coordinator and market operator in UGP; much like an air traffic controller, SPP coordinates WAPA’s transmission system in Iowa, Minnesota, Montana, Nebraska, North Dakota and South Dakota.

Beginning at midnight Feb. 9, SPP asked the transmission operators within its power grid to begin implementing “conservative operations,” a status used when SPP is operating its system conservatively based on weather or other threats. 

The severe conditions hit the grid with full force beginning the weekend of Feb. 13-14. That Sunday afternoon, SPP informed WAPA that it would likely need to declare an Energy Emergency Alert Level 1 starting at 5 a.m. on Monday. 

“When we heard about that, we started pulling out our emergency operation plans, and the Merchant group started talking with the Army Corps of Engineers to see what we could do to help in that situation,” said UGP Vice President of Operations Lloyd Linke.

Stressed to the limit

At all times, energy supply must match customer demand on the transmission system to avoid catastrophic failure. 

On Feb. 15, SPP’s grid reached a peak load of 43,661 megawatts. After expending its reserves and importing power from other regions, SPP faced a supply shortfall of 641 MW. At 10:08 a.m., it was forced to issue the first Energy Emergency Alert Level 3 in the organization’s 80-year history.

“Shortly thereafter, SPP directed its member utilities to institute rolling blackouts across much of its territory to protect the grid, and the communities that rely on it, from damaging and prolonged outages,” Linke said.

Under an EEA 3 order, member utilities decide how best to cut back their use based on their individual contingency plans. Due to the fast-evolving emergency operations, most utilities were initially unable to notify their customers in advance. 

On Tuesday, Feb. 16, WAPA was again directed by SPP to periodically shut off power on a rolling basis to maintain the integrity of the grid. As a wholesale hydropower provider, WAPA worked with its utility customers to implement and communicate controlled interruptions, while warning them to prepare for curtailments persisting through Thursday.

Twenty-one WAPA utility customers throughout UGP experienced outages for an average of 55 minutes, some of them multiple times for different loads. For some larger electric cooperatives, WAPA cut power at various delivery points at different times but never curtailed the same load twice.

In total, SPP temporarily interrupted electric service on two different days to reduce regional energy consumption. The first curtailment was by about 1.5% systemwide for 50 minutes Feb. 15 and again by about 6.5% for just over three hours Feb. 16. SPP cited inadequate supplies of natural gas, wind-forecast uncertainty and the persistent, widespread and extreme cold as the driving forces behind the shortage.

Mitigating actions

“Last week marked the first time SPP has ever had to direct controlled interruptions of service to our entire region,” said SPP President and CEO Barbara Sugg in a statement. “We did so only after exhausting every other option, including bringing emergency generation online, importing power from neighboring regions and more.”

SPP required utilities to appeal directly to consumers, urging them to reduce electricity and natural-gas use, both at work and home, and follow their local utilities’ guidance on conservation measures. This helped reduce overall system load and minimized the duration of the shortage. 

Fort Pierre, South Dakota, fired up its diesel-powered backup generators, which supplied the town with about 6 MW for 82 hours during the emergency. 

“WAPA would like to thank our impacted customers and the families, farms and businesses they serve in Upper Great Plains for their tremendous efforts to maintain the integrity of the grid,” said Acting Senior Vice President and Upper Great Plains Regional Manager David Neumayer.

By Saturday, Feb. 20, the energy shortage was over.

Pooling resources

WAPA worked with the Army Corps of Engineers Feb. 15-18 to provide significant generation increases from the Missouri River powerplants to support the grid. UGP and the Corps worked together to maximize hydropower output and closely monitor the system.

“UGP’s Power Marketing team worked with the Army Corps of Engineers to determine if they would allow for additional water flows beginning on Monday,” said UGP Vice President of Power Marketing Lori Frisk. “We aligned to minimize impacts during this event and optimized all available resources to support SPP and our customers.”

In coordination with WAPA, the Corps boosted hydro production at morning and evening peak hours with up to 740 MW per hour in additional generation. 

“Normally, the Army Corps of Engineers looks at factors like navigation, flooding, recreation and environmental restrictions to give us a water schedule of how much water they will allow to go through the powerplants each day,” Frisk said. “But, during the emergency, the agencies worked together to support the grid whenever and wherever it was needed most.”

WAPA and the Corps sent 22,500 megawatt-hours of additional hydropower to SPP between Feb. 15 and 18, enough to power between 700,000-800,000 homes. 

What made this possible was the unprecedented level of coordination and cooperation between the Corps, WAPA’s Merchant and Operations groups and SPP. 

“People made this response happen, not tools nor algorithms,” said Supervisory Energy Management and Marketing Specialist Neil Lindgren. “All branches truly made the most of their human resources throughout this entire event. The professionalism in thought, inclusion and communication was nothing short of impressive.”

Closing the gap

WAPA also purchased power off the spot market to make up the difference between available hydropower and the firm, or guaranteed, power contractually required by customers in the region.

“Pick-Sloan is marketed with firm obligations; to the degree we’re short, we have to buy—and we’re then exposed to market prices,” Neumayer said, referring to the hydropower UGP sells from the Pick-Sloan Missouri Basin Program—Eastern Division. 

WAPA maintains financial reserves to fill the gap when available energy falls below what is promised to customers, including $393 million set aside for purchase power and wheeling costs. Because of the complexities of the process for settling power purchases during a period of intense price volatility, it could take months to know the total cost of energy purchased during the emergency.

“Looking back, it is a really good thing WAPA did the work to ensure we have our purchase power and wheeling reserve strategy in place,” Neumayer said. “The authority to have the funding available really proves its value in times of unexpected price impact.”

The financial reserves provide stability and confidence that WAPA can weather difficulties like the one in February and continue to reliably supply its customers.

Challenges ahead

As the grid is pushed closer to the operational edge—with smaller margins for error—extreme weather events will continue to test the flexibility and resilience of utilities and their customers.

Key takeaways that WAPA gleaned include beefing up communication with customers and working with the Corps as quickly as possible. WAPA will also collect more data on what is at the other end of the lines that the organization is de-energizing. Advancements in these areas will go a long way toward rounding out WAPA’s response in the future.

“Any time that it’s the first time you implemented your plans, there’s always going to be room for improvement,” Linke said.

Note: Barendsen is a public affairs specialist.

Summit Substation in icy conditions

Cold temperatures, ice and snow can wreak havoc on energy systems. This happened in Texas and the Midwest in February and, as pictured, at Summit Substation near Watertown, South Dakota, in 2016.

Image depicting Fort Randall Dam

The Army Corps of Engineers built the Fort Randall Dam from 1946-56 in South Dakota, creating Lake Francis Case. Part of the Pick-Sloan Missouri Basin Program—Eastern Division, it is the 11th largest reservoir in the United States, and its hydropower facility is engineered to supply up to 320 megawatts, enough to power 245,000 homes. Photo courtesy of the Army Corps of Engineers.

Last modified on September 12th, 2023