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FERC, NERC, and Regional Entities Joint Review of System Performance During Winter Storms Gerri and Heather

The winter of 2023-2024 was the warmest ever recorded for the contiguous United States with an average temperature of 37.6 degrees Fahrenheit. Much to the disappointment of winter activity enthusiasts but to the excitement of a golfer like me that does not recall ever golfing in Minnesota in January or February. Despite the warm winter, between January 10 and 16, robust artic storms (named Gerri and Heather by the Weather Channel) with below normal temperatures swept across the United States and caused operational impacts to the bulk power system.

Due to the breadth of the storms and past bulk power system challenges with Winter Storms Uri and Elliott, the Federal Energy Regulatory Commission (FERC), along with the North American Electric Reliability Corporation (NERC), and the six NERC Regional Entities launched a joint review of bulk power system performance during storms Gerri and Heather. The joint review team took a different approach with this analysis than past winter storm analyses. The performance review focused on event observations from Balancing Authorities and other key entities gained through voluntary interviews and publicly available data sources. This allowed the team to make meaningful comparisons more quickly to findings and recommendations from past major winter storms.

The team presented results of the review at the FERC meeting on April 25, 2024, which were highlighted in a joint news release. A major takeaway from the review was that Reliability Coordinators and Balancing Authorities were successful in navigating challenges with unexpected loss of generation and higher than forecasted loads to avoid impacts in serving customer load during the extreme cold. Unlike past storms Uri and Elliott, there was no operator-initiated load shed during the event period. Overall, interviewed entities in the Eastern Interconnection indicated that operational experience from storms Uri (in 2021) and Elliott (in 2022) helped them better navigate challenges during storms Gerri and Heather.

Some of the observations by team members include:

  • Improved coordination among neighboring reliability coordinators and balancing authorities.
  • Enhanced communications to better inform key stakeholders of impending challenging conditions.
  • Better use of uncertainty analysis in different forecasts during the cold weather window to inform decision-making before and during the event.

During the storms, significant amounts of energy were imported in certain areas to navigate operational challenges. This highlights the importance of energy transfer capabilities and reinforces the importance of addressing the following recommendations from the Uri and Elliott reports.

  • Elliott Recommendation 10: Resource Planners and entities that serve load should sponsor joint-regional reliability assessments of electric grid conditions that could occur during extreme cold weather events.
  • Uri Recommendation 20: Adjacent Reliability Coordinators, Balancing Authorities and Transmission Operators should perform bi-directional seasonal transfer studies, and sensitivity analyses that vary dispatch of modeled generation to load power transfers to reveal constraints that may occur, to prepare for extreme weather events spanning multiple Reliability Coordinator/Balancing Authority areas like the Event

Overall, there were fewer generator outages observed during the cold weather period than past events in Uri and Elliott. However, some areas saw similar levels of generator outages as in past storms and outage levels overall were still significantly higher than an average winter day. While progress has been made with respect to generation availability during extreme cold weather, there is still work to do to continue to improve availability. MRO’s Generator Winterization Program is a valuable tool that MRO provides to interested entities looking to improve cold weather performance. Draft NERC Reliability Standard EOP-012-2, which was filed with FERC in February, sets mandatory reliability requirements to address effects of extreme cold weather on operating generation.

Despite challenges, the bulk power system performed better during Gerri and Heather than during Winter Storms Uri and Elliott. This indicates that recommendations and experience from prior winter storms have been acted upon to improve reliability. There is also recognition that no two winter storms are the same and differences in the timing and location of extreme cold weather can have different impacts on bulk power system reliability. While progress has been made, there is a continued need for entities to address recommendations from the Uri and Elliott reports and continue to coordinate and collaborate for improved reliability during extreme cold weather.

Mark Tiemeier, MRO Principal Technical Advisor