Despite bad weather and forced power plant outages the nation’s grid was reliable in 2023
Energize Weekly, July 3, 2024
Even in the face of extreme weather events and higher rates of forced outages at generating facilities, the U.S.-Canadian electric grid remained “reliable and secure” in 2023, according to the North American Electric Reliability Corp. (NERC).
“Over the past several years, a handful of extreme weather events have increasingly been the largest challenge to BPS [bulk power system] reliability, and the unprecedented magnitude of these events has dominated reliability trends,” NERC said in its 2024 reliability report.
In 2023, there were 58 weather-related events, including 16 winter storms, 24 wind and thunderstorms, 9 tornadoes, 8 hurricanes, and one wildfire, that led to outages. “The dominant cause of transmission outages was determined to be the weather type,” the report said.
Hurricanes caused the largest number of transmission problems with an average 154 outages per hurricane. The average for other types of extreme weather outages ranged from 40 to 59.
The 2023 weather events, however, were not as severe as the winter storms the country experienced in 2021 and 2022.
The analysis identified 11 large weather-related transmission outage events.
The largest was the Quebec wildfires that led to 180 outages between June 20 and July 16, and consisted of 101 small non-overlapping events. The outages were generally short, an average of 1.2 hours.
The second largest event was a winter storm and tornadoes on March 31, which caused 119 transmission outages in the Eastern Interconnection, which stretches from southern Canada, excluding Quebec, to Florida.
In the face of the bad weather and outages, NERC said that based on its severity risk index the worst-performing days in 2023 still performed better than the worst-performing days in prior years.
“Following these more routine, severe events in 2023, restoration times of transmission system outages were 10–20 percent better than in most prior years, and no load loss associated with Level 3 Energy Emergency Alerts occurred,” the agency said. Level 3 alerts direct utilities to prepare for severe weather and can include the use of rolling blackouts.
At the same time that grid operators faced weather challenges, they also saw a decrease in generation plant reliability.
“Forced-outage rates at conventional and wind generating facilities remain at historically high levels, exceeding rates for all years prior to 2021,” the NERC report said.
Coal-fired generation saw the largest increase in the weight equivalent forced outage rate (WEFOR), a measure of reliability, which rose to 12 percent from a 2014-2022 average outage rate of 10 percent.
Reduced maintenance on older coal units set to close and the need to cycle – ramp generation up and down, which is not easy with coal units – to accommodate variable generation, such as wind and solar, are hampering reliability, NERC said.
Hydropower units also experienced an increased annual WEFOR at 6.9 percent for the second time, following one in 2021 at 7.6 percent. The WEFOR for 703 wind plants, which are a variable generation source, was 191.1 percent for 2023.
“Forced outages of conventional generation peaked in 2021 and 2022 due to major cold weather events,” the report said. “But when those years are excluded, last year, despite no single major generation-impacting event, we had the third-highest forced outage rate on record, with a 7.8 percent weighted equivalent forced average rate.”
