ERCOT Sheds Load as Extreme Cold Forces Generators Offline; MISO, SPP Brace for Worsening System Conditions

Historically frigid temperatures across Texas forced 34 GW of generation—across all fuel types—off the Electric Reliability Council of Texas (ERCOT) system, prompting the grid operator to initiate rotating outages starting at 1:25 a.m. CST on Feb. 15. ERCOT said it expects outages will likely last at least through Feb. 16.

This article has been updated as of 3 p.m. CST, Feb. 15, to reflect new information received from ERCOT, MISO, and SPP.

The Midcontinent Independent System Operator (MISO) also confirmed it directed Entergy to shed load in Texas early on Feb. 15. “Sustained frigid temperatures and winter weather impacting the [MISO] South Region contributed to the loss of generation and transmission. This led to emergency actions in the region’s western portion to avoid a larger power outage on the bulk electric system,” it said.

Shortly after noon CST on Feb. 15, Southwest Power Pool (SPP) also began directing its member utilities to implement controlled outages to prevent more widespread uncontrolled outages within its 14-state balancing authority area. 

ERCOT, MISO, and Southwest Power Pool (SPP) had all issued calls for conservation on Feb. 14 in preparation for extreme cold weather that is expected to grip the nation and persist through a good part of the week. (Editor’s note: Texas Gov. Greg Abbott on Feb. 16 called for state lawmakers to make ERCOT reform an “emergency item.”)

At around 2:30 p.m. CST Monday, the Federal Energy Regulatory Commission (FERC) announced it was “closely monitoring” the extreme conditions occurring in much of the country and the impact they are having on electric reliability. FERC Chairman Rich Glick said he directed FERC staff to coordinate closely with the regional transmission organizations and independent system operators, utilities, the North American Reliability Commission, and regional reliability entities “to do what we can to help.” Glick said FERC will examine the root causes of the reliability events “in the days ahead.” 

ERCOT Takes Extreme Measures, Grapples with Overwhelming Freeze-Related Outages

ERCOT, which serves 90% of the state’s load has been bracing for the extraordinary measure, warning for days that an expected “Arctic outbreak” could set a new all-time winter peak demand record. The previous winter peak-demand record—of 65,915 MW, set on Jan. 17, 2018, between 7 and 8 a.m.—was broken on Sunday, Feb. 14, between 6 and 7 p.m., reaching 69,150 MW.

ERCOT President and CEO Bill Magness in a statement on Sunday morning noted the region was already grappling with higher-than-normal generation outages due to “frozen wind turbines and limited natural gas supplies available to generating units.”

But after the Feb. 14, 7 p.m. peak, beginning around 11 p.m., “multiple generating units began tripping offline in somewhat rapid progression due to the severe cold weather,” ERCOT Senior Director of System Operations Dan Woodfin told reporters on Monday morning. “As a result of this decreasing supply and continued high demand, we began to see diminishing reserves.” 

Woodfin said ERCOT implemented its emergency operation plan to make sure it could maintain the balance between supply and demand on the system. At the highest point, it asked transmission operators to reduce 16.5 GW of load—enough power to serve approximately two million homes. “Every grid operator and every electric company is fighting to restore power right now,” said Magness said in a statement on Monday.

“The way this works  is we determine how much reduction in demand is needed to maintain that supply demand balance, and we tell the transmission owners around the state how much reduction we need, and then they determine where and how to implement those reductions on their systems,” Woodfin said. “Each transmission owner has a load ratio share of the amount of demand that they need to reduce, so if we say we need to reduce 1,000 MW on the system, and one of the transmission owners has 20% of the load on the system, then they have to figure out how to reduce the load on their system by 20% of that amount that we have said that we need to reduce,” he said.

ERCOT said rotating outages will continue until there is sufficient generation brought back online to meet the demand on the system. “At this time we anticipate that we’ll need to continue these controlled outages at some level for the rest of today and at least the first part of tomorrow—perhaps all day tomorrow—because of the severity of the event and the amount of load that’s had to be shed,” Woodfin said. The outages represent “more megawatts and longer than we’ve ever had in the past,” he noted. 

Woodfin did not precisely break out the generation capacity that ERCOT lost leading up to its 1:25 a.m. decision to shed load, but he noted: “Most of those generators that went offline during the night, last night, were either—there a few additional wind generators that went offline during the night—but the majority of them were thermal generators, like generation fueled by gas, coal, or nuclear, And so most of the plants that went offline during the evening and morning today were fueled by one of those sources.”  

As of 10:30 a.m. CST on Feb. 15, the aggregate of capacity that was unavailable was 34 GW. At the end of 2020, ERCOT had 77.2 GW of installed resources. That suggests the grid operator has lost more than 40% of its operable capacity.

Frozen Wind Turbines, Limited Gas Supplies

Why these sources tripped is not yet known with certainty, which makes forecasting when supply will return to normal complex, Woodfin suggested. “There’s some limited reporting that [the generators do] but we’re certainly going to be doing our normal event analysis that we do. This will probably be bigger than our normal event analysis, but we will certainly go through and figure out why those things happened,” he said.

The event is ERCOT’s first major winter emergency since February 2011, when another unusually bitter cold snap forced 7 GW of generation offline, prompting the entity to initiate rolling blackouts. In the summer that year, ERCOT was forced to cut power to large industrial users to avoid rolling blackouts as the state grappled with depleted reserve margins and surging power demand during a long heat wave and a devastating drought. As a result of the February 2011 event, a Federal Energy Regulatory Commission and North American Electric Reliability Corporation task force recommended that states mandate that generators winterize their power plants.  

ERCOT said last week it had called on generators to take necessary steps to prepare their facilities for the expected cold weather. It said it urged generators to review fuel supplies and planned outages and implementing winter weatherization procedures. The grid operator said it was also working with transmission operators to minimize transmission outages that could reduce the availability of generation or otherwise impact the ability of the system to serve demand.

On Sunday, as Gov. Gregg Abbott sought and obtained federal assistance in response to the severe winter storm, the Public Utility Commission of Texas (PUCT) echoed a call from ERCOT for electricity conservation, warning: “Narrow margins between cold-driven demand and the supply of available power across the state are expected to occur periodically through Tuesday.” 

ERCOT, an energy-only market (where costs must be recovered with revenues from energy production and operating reserves), has been working to build its planning reserve margins to boost reliability after debacles in 2018 and 2019, when it experienced historically low margins owing to plant retirements. In December 2020, ERCOT said that while its current system-wide peak demand record is 74,820 MW, set on Aug. 12, 2019, between 4 and 5 p.m., the planning reserve margin for summer 2021 is forecasted to be 15.5%.

ERCOT’s 2020 Generating Capacity. At the end of 2020, ERCOT had 77.2 GW of installed resources. Courtesy: ERCOT

However, ERCOT has said it has the tools and procedures in place to maintain a reliable electric system during tight grid conditions. “If power reserves drop too low, ERCOT may need to declare an Energy Emergency Alert, or EEA,” it said. “Declaring an EEA allows the grid operator to take advantage of additional resources that are only available during scarcity conditions. There are three levels of EEA, and rotating outages are only implemented as a last resort to maintain reliability of the electric system,” it said.

PUCT Chairman DeAnn Walker urged all power consumers across the state to heed the call for conservation. “The lowest temperatures Texas has seen in decades necessitate a shared response across the state, from households to factories,” she said. “Along with the tools ERCOT uses to maintain the reliability of the grid, common sense conservation also plays a critical role in our state’s endurance of this challenge.”

SPP Initiates Load Shedding—for the First Time in its History

Exhausting all its available reserve energy as a bitter cold snap endures over its 14-state balancing authority area, Southwest Power Pool (SPP) began directing its member utilities to implement controlled power interruptions to prevent more widespread uncontrolled outages. 

Under the measure implemented shortly after noon CST on Feb. 15, the regional transmission organization that oversees the bulk electric grid and power market in the central U.S., from Oklahoma to North Dakota, said it instructed its member’ transmission system operators to reduce power demand by an amount needed to prevent further uncontrolled outages. “Individual utilities will determine how best to curtail their use by the required amount based on their own emergency operating plans,” it said. 

SPP declared declared an Energy Emergency Alert (EEA) Level 1 on Sunday, Feb. 14,  anticipating “tightening conditions” over the next several days. It  moved to an EEA Level 2 beginning at 7:22 a.m. CST,  Feb. 15, and quickly followed that declaration with an EEA Level 3 at 10:08 a.m. CST. 

The grid entity said the directive to implement load shedding was a last resort. “In our history as a grid operator, this is an unprecedented event and marks the first time SPP has ever had to call for controlled interruptions of service,” said SPP’s executive vice president and chief operating office Lanny Nickell. “It’s a last resort that we understand puts a burden on our member utilities and the customers they serve, but it’s a steep we’re consciously taking to prevent circumstances from getting worse, which could result in uncontrolled outages of even greater magnitude,” he said. 

Earlier on Monday, SPP said it was coordinating “closely” with members and market participants to “respond to high demand for electricity, inadequate supply of natural gas, and wind-forecast uncertainty among other variables.” 

The entity also issued a declaration of conservative operations that began at midnight CST, on Feb. 15 and extends 48 hours “to mitigate the risk of more widespread and longer-lasting outages.” By declaring conservative operations, SPP is signaling to its member company utility operators that they should operate conservatively.

“To bolster system reliability, SPP may require generating units to be available for upcoming operating days with notifications for commitment issued multiple days in advance. SPP took these steps in preparation for the extreme weather conditions already experienced and expected over the next couple of days,” it said. 

An EEA1 signals that “SPP foresees or is experiencing conditions where all available resources are scheduled to meet firm load obligations and that we may be unable to sustain its required contingency reserves,” it said. 

An EEA Level 2 is triggered “if SPP could no longer meet expected energy requirements and was considered energy deficient, or if SPP foresaw or had taken actions up to but excluding the interruption of firm load obligations. At this point, SPP would have utilized available energy reserves and would have requested assistance from other neighboring utility operators,” it said. 

According to the National Weather Service, the “Arctic outbreak” is expected to send frigid air and dangerously cold wind chills across the heartland, pushing down temperatures to historic lows as far south as southeastern Texas. A major winter storm will develop over the southern Plains on Feb. 15, lifting into the Northeast through Tuesday with a large area of snow, sleet, and freezing rain expected, the NWS predicts. Courtesy: NWS

MISO Sheds Load in Texas

MISO, which operates a grid that stretches across 15 U.S. states in the Midwest, the south, and the Canadian province of Manitoba, on Feb. 15 said its emergency action early on Monday morning to the region’s western portion to avoid a larger power outage on the bulk electric system prompted rolling outages for customers in Southeast Texas.

“We fully committed every available operating asset before the event to lessen the impact on our system, but conditions eventually deteriorated to a point where demand exceeded supply,” said Renuka Chatterjee, executive director of System Operations at MISO. “The accelerated change in conditions led us to our last resort in order to maintain grid reliability and we are in direct communication with our members to support their restoration efforts in the affected areas.”

MISO, which has worked closely with members to maintain system reliability amid the extreme conditions, on Monday said “members worked together to identify the worst-case scenarios to limit the effects of temporary power supply interruptions to those areas that will provide the most relief.” That plan focused on the forecasted load demand and expert weather forecast as well as the risks associated with generation availability and transmission capacity across the region, it said.

Chatterjee on Sunday noted current load forecasts in the South Region were approaching an all-time winter peak of 32 GW in comparison to last year’s peak of 27 GW. That was “making this a very difficult situation,” she said. “We are in constant contact with our members and our partner ISO/RTOs to ensure the reliability of the bulk electric system.”

MISO’s declared Conservative Operations will be effective from Feb. 14 at 12 p.m. EST until Feb. 16 at 11:59 p.m. EST. MISO has also declared a “Cold Weather Alert” that expires on Tuesday night for entities in the entire Balancing Authority Area. Finally, MISO has also issued a Maximum Generation Capacity Advisory for the South region effective Feb. 15 at 9 a.m.

So far, MISO’s market functions are performing as designed, the grid operator said. “Operators follow established procedures and rely on extensive training and preparation to manage this event,” it said.

Sonal Patel is a POWER senior associate editor (@sonalcpatel@POWERmagazine).

SHARE this article