MISO should have adequate capacity to navigate winter but could still face abnormal weather-related generation outages or a load-shedding event, RTO officials said Wednesday.

The RTO expects to have 146 GW of available capacity to manage an expected 104-GW winter peak, 5 GW less than its all-time winter peak on Jan. 6, 2014.

Executive Director of Real-Time Operations Rob Benbow said anticipated electricity usage paired with the “outages we have planned” show adequate reserves.

But as usual, a combination of high demand and unexpectedly high generation outages could put MISO operations in jeopardy.

“I think we all know that unforeseen events and outages can change our position, and we will work with members to mitigate issues and ensure the reliable and efficient operation of the grid,” Benbow said during a winter readiness teleconference.

“I believe it’s important to spend time on winter readiness just as much as we talk about summer readiness,” he added.

Using a high-load, low-generation forecast, MISO said it could exhaust all 10.5 GW of its load-modifying resources (LMRs) on a January peak day and be forced to order load-shedding from members. Using the more likely forecast provided by its market participants, a high-demand, peak day in January containing a more typical number of outages could still force MISO to declare an emergency to access some of its LMR stack. If winter conditions are harsh enough, the grid operator said it could tie its 109-GW all-time winter peak.

Resource Adequacy Coordination Engineer Eric Rodriguez said December and January bring the highest risk of a maximum generation event.

“MISO is planning minimal risk in February, which appears to be a preferential time to schedule generation outages,” Rodriguez said.

Last winter, MISO’s generation outages trended lower than its five-year average, averaging about 22 GW.

The National Oceanic and Atmospheric Administration is forecasting above-average temperatures this winter in MISO South and lower-than-normal temperatures for Minnesota, Wisconsin and the Dakotas (Zone 1). The agency also predicts more precipitation than usual in MISO Midwest and a drier winter for South.

“The past 10 winters have been within 10% of NOAA’s predictions,” Rodriguez said.

Director of Balancing and Interchange Operations Tag Short said MISO has undertaken dramatically more winter preparation since the polar vortexes and subsequent maximum generation events of 2014 and 2019 and the two-day MISO South emergency in January 2018. Since the Midwestern arctic blast in 2019, the RTO has been including the cold-weather cutoff thresholds of wind generators.

“We do have a pretty good ledger now of extreme temperatures,” Operational Forecast Planner Adam Simkowski said, adding that MISO now factors public building and college closures into its load forecasting. He said polar vortexes tend to produce more subdued, weekend and holiday-style forecasts.

MISO’s Geoff Brigham also said generators this winter can turn to the RTO’s multiday operating margin forecast, launched last November, to help make commitment decisions. The forecast shows a week-ahead expected supply picture.

The RTO is also exploring publishing multiday outage and derate information, Brigham said.

Generation and Balancing Authority Operator Michael Carrion said MISO’s approximately 200 natural gas generators representing 70 GW have ample access to basins, pipelines and storage by virtue of the RTO’s broad territory.

Carrion reported that the Midwest’s natural gas storage levels are above the five-year historical range and “nearing the five-year maximum storage threshold due to strong production, reduced load and relatively mild temperatures.”

MISO also doesn’t expect any unusual transmission limitations this winter.

Meanwhile, NERC is still making progress on developing cold weather standards, spurred by MISO South’s early 2018 emergency, staff said. (See FERC Orders Cold Weather Reliability Standard.)

Principal Adviser of Standards and Assurance Bobbi Welch said NERC has landed on a scope for the cold weather preparation rules, which will rely on existing plant winterization standards and communications on generation capability.

The standard might be nothing more than business-as-usual, especially for generator owners and operators in the northern portions of MISO’s footprint, Welch said.

“They’re hoping that this will make it more palatable,” she said. “It’s going to take a look as a system on how we get ready for winter weather.”

In a 2019 report on the MISO South emergency, FERC and NERC concluded that generation owners failed to properly winterize their equipment, contributing to the supply crunch.

Welch said the standards should be ready for use in late 2021, “about a one-year horizon.”

A Rising Winter Risk

The cold weather standards are being developed as MISO devotes more time to assessing an emerging wintertime loss-of-load risk.

The RTO has recently said it could define unique seasonal system reliability requirements, hold seasonal capacity auctions and use risk assessments beyond its summer-emphasized loss-of-load study. (See MISO Lays Out Seasonal Capacity Options.) The options would have MISO moving away from summer peak modeling and forecasting in favor of determining multiple loss-of-load risk hours throughout the year, called resource adequacy hours.

MISO’s current loss-of-load modeling tends to underestimate wintertime risk, a trend that will be exaggerated as the footprint adds more solar generation, MISO analysis shows.

During a special teleconference Monday, MISO Director of Research and Development Jessica Harrison said stakeholders are interested a monthly or seasonal division of capacity auctions.

“We want to land on a model that mitigates risk under a variety of resource portfolios,” Harrison said, adding that any resource adequacy design must also be practical for MISO to implement.

Senior Manager of Resource Adequacy Coordination Lynn Hecker said it would be easy enough for MISO to incorporate new sub-annual modeling inputs.

Using an expected unserved energy calculation — where MISO calculates the expected amount of energy when load is set to exceed generation — the RTO found risk in January, February, May and December, in addition to the prevailing risk in June, July, August and September identified under summer peak loss-of-load modeling.

Using a five-year-out generation portfolio based on queue projections, MISO found risk in every month except April, November and December, with the most pronounced risk occurring in February and September.

Hecker said results using the revised inputs generally track with emergency events MISO has experienced under its current portfolio. Most of its roughly dozen emergency declarations since 2016 have occurred outside of summer months.