Nine months after extreme cold weather gripped Texas and the South Central U.S., FERC, the North American Electric Reliability Corporation (NERC) and NERC’s regional entities issued a final report examining the impact the February 2021 freeze had on the bulk electric system.

The cold weather event – also known as Winter Storm Uri – caused numerous outages, derates, or failures to start at electric generating plants scattered across the region. The Texas grid operator (Electric Reliability Council of Texas or ERCOT) ordered a total of 20,000 MW of rolling blackouts to prevent grid collapse; this represents the largest manually controlled load shedding event in U.S. history. More than 4.5 million people in Texas lost power – some for as long as four days. Tragically, the loss of electricity caused more than 200 deaths in Texas. 

“The final report on Winter Storm Uri is a sobering analysis that highlights the significant work that needs to be done,” said FERC Chairman Richard Glick. “The devastating effects of extreme cold on our bulk power system’s ability to operate in 2011 and now, 2021, must not be allowed to happen again. We have a duty to protect the bulk power system and public safety and we will do just that.”

The report found a combination of freezing issues (44.2 percent) and fuel issues (31.4 percent) caused 75.6 percent of the unplanned generating unit outages, derates, and failures to start. Of note, protecting just four types of power plant components from icing and freezing could have reduced outages by 67 percent in the ERCOT region, 47 percent in the Southwest Power Pool (SPP), and 55 percent in the Midcontinent Independent System Operator (MISO) South regions. Natural gas-fired units represented 58 percent of all generating units experiencing unplanned outages, derates, or failures to start. The remaining portion was comprised of wind (27 percent), coal (6 percent), solar (2 percent), and other generation types (7 percent), with four nuclear units making up less than 1 percent.

The final report provides more details:

• 81 percent of freeze-related generating unit outages occurred at temperatures above the units’ stated ambient design temperature.
• 87 percent of unplanned generation outages due to fuel issues were related to natural gas, predominantly related to production and processing issues, while 13 percent involved issues with other fuels such as coal or fuel oil.
• Natural gas fuel supply issues were caused by natural gas production declines, with 43.3 percent of natural gas production declines caused by freezing temperatures and weather, and 21.5 percent caused by midstream, wellhead, or gathering facility power losses, which could be attributed either to rolling blackouts or weather-related outages such as downed power lines.

Key Takeaways from MISO’s February 2021 Arctic Event Report are consistent with the findings from the FERC / NERC report, including:

• The need for increased generator winterization requirements,
• The need for gas industry winterization and the importance of coordination across the electric and gas industries
• The need for good situational awareness leading up to and during events (including enhanced weather, load, and outage forecasting
• More flexibility and coordination of load shed protocols during winter events, given the recognition that extreme weather events are becoming more frequent and have the potential to take a major toll on public safety

The FERC / NERC report lists 28 specific recommendations, many of which do not directly involve MISO or other RTOs.  For example, NERC has recommended enhanced winterization standards for generator operators and recommended that federal and state policymakers institute natural gas system winterization.  MISO is reviewing all recommendations and looks forward to participating where appropriate to ensure the reliability of the bulk electric system.