An Arctic blast felt by a large portion of North America is causing reliability turmoil within some segments in its bulk power system, forcing reliability coordinators to declare emergencies, issue conservation warnings, or shed load.
TVA, Grappling With Demand Surge, Resorted to Load Shed
Temperatures averaging the single digits across the Tennessee Valley Authority (TVA) prompted the federal corporation—the regional reliability coordinator—and local power companies to act proactively “to temporarily reduce power supplies to localized areas.” TVA said the disruptions were needed “to maintain grid stability for 10 million people across seven states.”
Local power companies shed their power load “at TVA’s direction” on Friday and again on Saturday morning. On Saturday, the load shed—planned intermittent interruptions to support system reliability—began at 7 a.m. and ended at around 11 a.m. “Each local power company is executing its own plans to minimize the impacts on the communities they serve,” Ashton Davies, a TVA spokesperson, told POWER on Dec. 24.
TVA has partnerships with 153 local power companies across seven states. These are “industrial customers who are assisting us to ensure the reliability of the system during what the National Weather Service has called a ‘once-in-a-generation’ storm impacting the majority of the country,” she said.
Nashville Electric Service, one of the 12 largest public power utilities in the nation, at 7 a.m. said TVA required a 10% reduction in load shed. It warned customers in Davidson County and surrounding counties in Middle Tennessee that they would experience about a 10-minute power outage per hour until power load stabilized. The power company said it was additionally dealing with malfunctioning breakers and burning wires due to excessive load.
#NESServiceAlert At this hour, TVA has downgraded to 5% power interruption conservation, creating 10-minute outages every 1.5-2 hrs. Most customers in the Hermitage and Crutcher St areas are back on. Some individual outages could remain and will continue to be repaired.
— Nashville Electric Service (@NESpower) December 24, 2022
TVA said the issue was rooted in an unprecedented demand surge. “For the 24 hours on Friday, Dec. 23, TVA set an all-time TVA record for energy delivery: 740 GWh. The previous record was 706 GWh in 2018. We also set an all-time winter peak power demand record: 33,425 MW. It is also the third-largest peak demand in TVA’s history,” she said. “Normally, during this time of year, our system manages demand of around 24,000 MWs.”
In addition to the intensified demand, “a limited number of TVA’s generating facilities did not operate as expected during this event resulting in a loss of generation,” Davies said. “Such events are part of TVA’s plans, and we have teams working 24/7 to return those units to service as soon as possible.”
Duke Energy Sheds Load In the Carolinas
Duke Energy, one of the largest investor-owned utilities in the U.S., at 6:30 a.m. on Dec. 24, announced it had begun “short, temporary power outages” in North Carolina and South Carolina to protect the energy grid “against longer, more widespread outages.”
The company said it expects load shedding to continue until 9 a.m. today. “Load shed rotates in 15–30-minute blocks though that timing may vary.”
Update: Duke Energy has ended the load shed request. All power should be restored. Thank you for your patience.
— Pee Dee Electric NC (@PeeDeeElectric) December 24, 2022
MISO Declares Generation Emergency
The Midcontinent Independent System Operator (MISO) on Dec. 23 declared a maximum generation emergency event at 5:23 p.m. and stepped it up to a Level 2 minutes later, owing to higher forced generation outages than forecasted load.
While the reliability coordinator that serves 15 U.S. states and the Canadian province of Manitoba terminated the event at 8:35 p.m., it declared “conservative operations” until noon on Dec. 24 for its central and north regions. MISO cited concerns related to “extreme cold, generation outages, and neighboring [regional transmission organizations (RTOs)] struggling to serve load.”
The Southwest Power Pool (SPP), which has members in 14 states across the central U.S., also declared an Energy Emergency Alert (EEA 1) on Friday at 8:27 a.m., ending it at 10 a.m. The reliability coordinator pointed to “effects of widespread and extreme cold,” which led to new records, it said. “SPP set a new record for electricity use during the winter season on Dec. 22, with load exceeding 47,000 MW. The previous record was 43,661 MW, set Feb. 15, 2021,” during Winter Storm Uri, an event that precipitated the worst U.S. reliability crises in recent decades.
The grid entity had previously issued a resource advisory on De. 22 for its entire balancing authority footprint in the Eastern Interconnection, anticipating its end at noon on Dec. 25. That remains in effect, SPP said.
PJM Says Risk of Rotating Outages ‘Very Real’
PJM Interconnection, operator of the nation’s largest grid, which serves 65 million people in 13 states and the District of Columbia, late on Dec. 23 also urged the public in its region to conserve electricity until 10 a.m. Dec. 25. The call was the region’s first since the 2014 polar vortex storm crisis, when the region had scrambled to meet demand with 22% of its generation capacity—including coal, gas, and nuclear—out of service.
“Demand for electricity is expected to increase in the PJM region and the regions neighboring PJM because of the extremely cold weather,” the grid operator said on Friday. While the grid operator is monitoring the power supply conditions and would do everything to keep power flowing in the region, it said it would take additional steps “such as reducing voltage.”
At 9 a.m. on Saturday, Duke Energy confirmed that PJM had notified member utilities in Ohio and Kentucky that Midwest power supplies are “tight.” Responding to a PJM request for voluntary energy conservation, Duke Energy urged customers to conserve energy. “In the event that additional measures are necessary, Duke Energy would begin emergency temporary interruptions of service to customers to extend available power generation and help maintain operations until additional power is available,” it warned.
The risk of rotating customer outages “is very real,” warned PJM Senior Vice President of Operations Mike Bryson in an 11 a.m. update on Saturday.
PJM’s peak power forecast for Dec. 24 was 133, 727 MW at 5 p.m.—7.4 GW more than its forecast peak for the day before. As of noon on Dec. 24, it had a total available capacity of 128,953 MW, about 9% renewables.
At around 5:30 p.m., stress on the grid prompted PJM to take the rare action of issuing a level 2 energy emergency alert (EEA 2). The alert ended at 8:30 p.m., but PJM at 10:30 p.m. issued a Maximum Generation Emergency/Load Management Alert and an EEA1, which has not ended. The measure essentially provides “an early alert that system conditions may require generation to be loaded above the normal economic limit or if Demand Response is projected to be implemented,” the grid operator said.
At 9:30 a.m. on Dec. 25, PJM finally ended its call of conservation after a morning peak of about 118,000 MW. It said it does not anticipate “issues serving the forecast peak load of 123,000 MW on Dec. 25.”
DOE Grants ERCOT Section 202(c) Order to Preserve Reliability
The Electric Reliability Council of Texas (ERCOT), which has implemented several grid improvements since its Winter Storm Uri debacle, said it was closely monitoring demand under the frigid weather conditions. In an operating condition notice on Dec. 16, it said that temperatures would meet ERCOT’s criteria of 25 degrees or lower in the Austin/San Antonio and the Dallas Fort Worth areas between Thursday, December 22 through Monday, December 26.
The grid operator was still carefully watching conditions as peak demand shattered records on Friday. Demand soared to 74 GW Friday morning, surpassing the previous winter record of 68,871 MW during Winter Storm Uri. “This is the deepest freeze in Texas (other than Uri, when we don’t know what demand would have been without the blackouts) since electric heating jumped. That makes for lots of uncertainty in the demand forecasts,” noted Daniel Cohan, an atmospheric scientist at Rice University.
ERCOT is forecasting an ample margin tonight, but that’s assuming that tonight’s demand gets nowhere near the 73 GW from last night (which was 8 GW above expectations) despite similar temperatures. With winds slow, conditions will be tight. pic.twitter.com/VJxTIJVqYs
— Daniel Cohan (@cohan_ds) December 23, 2022
ERCOT’s concerns have been compounded by operating difficulties faced by power plants due to cold weather or gas curtailments. An estimated 11 GW of thermal generating units, 4 GW of wind generators, and 1.7 GW were in outage as of Dec. 23. The grid operator late on Friday asked the Department of Energy (DOE) for a Section 202(c) emergency order to allow maximum operation of specified generators, unfettering them from state emissions requirements, in the event outages units did not return to service or if other units went out. The DOE granted the order, and it will be in effect until Dec. 25, 10 a.m.
Alberta Declares an Energy Emergency After Cold Affects Generators
The Alberta Electric System Operator (AESO), a reliability coordinator for the Canadian province’s power grid, declared a grid alert on Dec. 20 after setting an all-time peak demand of 12,187 MW (its last peak was 11,939 MW in January 2022). High demand and a trip at the 463-MW Keephills 3, a natural gas–fired plant, prompted another two grid alerts on Dec. 21.
AESO said the tight conditions have generally been caused by“ frigid temperatures” that “affected some generation facility operations,” and demand, which climbed to a new record of 12,193 MW.
Editor’s note: Last updated Dec. 25, 10:32 p.m. CST.