Dive Brief:
- Forced-outage rates at conventional and wind generating facilities “remain at historically high levels, exceeding rates for all years prior to 2021,” the North American Electric Reliability Corp. said Thursday in its 2024 State of Reliability, which reviews the previous year’s grid performance.
- The electric grid remained “reliable and resilient" in 2023, with no firm load shedding during energy emergencies and quick recovery following severe storms in the U.S. and wildfires in Canada, according to the report. Performance was aided by mild weather and enhanced preparation measures, NERC officials said.
- Forced outages of conventional generation peaked in 2021 and 2022 due to major cold weather events. 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% weighted equivalent forced average rate,” or WEFOR, Jack Norris, a performance analysis engineer with NERC, said on a call with reporters.
Dive Insight:
Reliability metrics show 2023 “was a great year in regards to the [bulk power system] getting power to end use customers,” Norris said. “That isn't to say that last year was without challenges, though.”
The rising forced-outage rates are a concern, and retiring coal plants are increasingly being replaced with a mix of inverter-based resources which have had their own reliability issues, NERC said. But there is also reason for optimism regarding IBR issues, with recent software fixes leading to reliability improvements, officials said.
Coal units in 2023 had a WEFOR of about 12%, Norris said, compared with their average of 10% between 2014 and 2022.
“While this 2% difference may not sound like a big change, for reference, most other unit types have remained within a percentile over the same period, and this is a continuation of increasing WEFOR rates for coal that we've been seeing over the last several years,” Norris. said.
Coal’s rising outage rates also align with what NERC has heard from industry — “that reduced maintenance on older coal units, as they're being phased out, and increased cycling to accommodate variable energy resources, are having a negative impact on these units’ reliability,” Norris added.
Wind generation’s forced-outage rate also continues to increase, up to 18.9% overall compared with 18.1% in 2022, NERC said. It is not an exact comparison to the WEFOR used to measure conventional generation performance, however, but "the continued increase is of concern given the growth in wind generation over recent years.”
NERC’s report also found a continuation of inverter-based resource ride-through issues, where solar, wind or battery generation may trip offline or reduce output in response to grid disturbances. It cited events in 2022 and 2023 where there was an unexpected loss of output from solar and battery facilities.
“The unexpected loss of generation and lack of ride-through support from these types of resources create system stability challenges,” NERC’s report said.
A December report from NERC found owners and operators of some IBRs are failing to follow voluntary operational guidelines, putting about 5,200 MW of bulk electric system solar at a higher risk of tripping offline.
But there has been progress around the issue, Norris said.
“Utilities and plant owners involved in these events have been working with inverter manufacturers to improve ride through capabilities of existing resources through software updates,” and performance improvements are being seen, Norris said. There are “clear indications that while there is definitely a ride-through issue with a large portion of currently in-service inverter-based resources, when the appropriate changes are implemented they can be greatly alleviated. “
