MISO is still collecting data and reviewing the actions it took during a massive cold spell that gripped most of the U.S. in mid-February.

Frigid temperatures Feb. 14-16 across most of the RTO’s footprint created paper-thin — and then nonexistent — reserve margins, particularly in MISO South. In all, MISO temporarily interrupted load Feb. 16-17 in parts of Southeast Texas, South and Central Louisiana, and South-Central Illinois. The rotating outage orders ended Feb. 17 at 1 a.m. EST.

“There’s just so much to still unpack from last week. … There’s going to be so much information coming out in the next few weeks,” MISO Senior Director of Operations Planning J.T. Smith said during a Reliability Subcommittee teleconference Feb. 25.

Smith said while operations and actions taken were similar to previous cold weather events in MISO South, the biggest dissimilarity was how far-reaching the arctic blast was.

“This was a more widespread cold weather event,” Smith said. “This time our neighbors weren’t as spared.”

He said the frigid air brought rain and snowstorms in addition to a band of ice storms that traveled through southern portions of the footprint.

“It wasn’t just cold weather, it was also severe weather,” he said.

The National Oceanic and Atmospheric Administration said nearly three-quarters of the contiguous U.S. was blanketed in snow Feb. 16.

After MISO declared the grid stable on the afternoon of Feb. 17, the South region briefly slipped back into an emergency event.

Smith said the RTO knew a week in advance that a polar vortex was imminent and began reaching out to members for their generation availability. Complicating matters, he said, was the Presidents’ Day gas trading holiday on Monday. He said MISO urged members to secure all fuel needs during gas clearing on Friday.

“We tried to be as thoughtful as possible on the front end of it, but once we got into real-time … we saw the extreme cold on the generation and transmission become much more stressful,” he said.

Smith said MISO issued multiple emergency declarations as it became clear the system couldn’t support the demand and overcome forced outages and fuel scarcity. He said energy was initially able to flow east to west to SPP, but those flows ground to a halt as the situation deteriorated.

“To make sure we didn’t lose more, we had to shed some load in a couple different instances,” Smith said.

He said the grid operator shed roughly 700 MW on the evening of Feb. 16, but he did not have numbers for the other events.

“There were a lot of things moving at the same time. It truly was an unprecedented environment that happened last week. There will be a lot of conversation,” he promised stakeholders. He said staff would offer more details and a timeline of the event at upcoming stakeholder meetings.

‘Mixed Bag’

It usually takes the grid operator a few months to collect data and publicly present a detailed review of congestion, import capability, generation outages and emergency response performance.

Smith said MISO navigated several transmission constraints and multiple emergencies in separate parts of the footprint because of a combination of unavailable fuel supply, generation trips, system operating limits and transmission congestion.

“It was a mixed bag all across all regions. It wasn’t just one area; there were outages all over the footprint,” he said.

In all, Smith said roughly 60 GW of capacity was unavailable at different times across the event.

MISO had predicted “minimal risk” throughout February in its annual winter preparedness workshop in the fall. It originally said January held the lion’s share of wintertime risk and that by February, generator maintenance outages could ramp up. (See MISO: Winter Could Get Tricky Despite Forecast.)

“We were in February. We’re usually past the risk by the end of January. We had some units that were getting ready to get on outages that our membership worked to move. In fact, one of our members had to move a planned outage twice because the cold lasted so long,” Smith said.

January operations were mild compared to February’s wild conditions. MISO’s January load averaged 76.2 GW with a “mild” 91.3 GW peak, the lowest January peak in four years, Smith said.

“Overall, it was a fairly benign month,” he said.

Guinea Pigs

Until now, MISO had recently been hosting short, uneventful meetings of its Reliability Subcommittee.

“Something tells me our next meetings won’t be so abbreviated. … I think we’re going to be rolling up our sleeves for the next several meetings,” RSC Chair Ray McCausland said during a MISO Advisory Committee teleconference Feb. 17.

McCausland said MISO may schedule joint meetings of its Market, Resource Adequacy and Reliability subcommittees, like it did in the wake of Hurricane Laura.

The RTO’s load shedding orders were much shorter than ERCOT’s sustained outages, largely sparing it the public ire that the Texas operator continues to face. (See ERCOT Provides ‘Explanations, not Excuses’.)

A week ago, MISO executives defended its last-resort emergency actions.

“MISO operators are highly trained to respond to multiple large-scale disruptions that can occur during tight operating conditions,” said Executive Director of System Operations Renuka Chatterjee. “We prioritized these challenges and made quick decisions to protect the integrity of the bulk electric system.”

Prior to last week’s deep freeze, MISO was pursuing a redesign of its resource adequacy construct, which includes more attention on wintertime reliability risks, seasonal capacity auctions and a pivot to an “available capacity” accreditation proposal, where accreditation values are rooted in generators’ past performance.

The Advisory Committee will hold a discussion on the potential new resource adequacy design during MISO’s quarterly Board Week in March, which will undoubtedly feature talk on the winter emergencies.

Clean Grid Alliance Executive Director Beth Soholt asked if MISO’s resource adequacy rethink will sufficiently address challenges unearthed in the deep freeze, which she said included performance issues across all resource types — frozen coal piles, unavailable pipelines and iced turbines.

“I think every resource type has had problems, in particular across Texas,” Soholt said during an Advisory Committee teleconference Feb. 17. “Are we adequately factoring this in?”

Resource Adequacy Subcommittee chair Chris Plante said MISO’s available capacity accreditation proposal should take an unbiased measure of resource availability.

Madison Gas and Electric’s Megan Wisersky said no other capacity market uses an available capacity accreditation and the concept remains unproven.

“We’re sort of guinea pigs in this. This is untested. I’m not saying it’s good or bad; we’re just guinea pigs,” she said.