Powering Strong Communities

Extreme Weather Continues to Threaten Grid Reliability: NERC

Extreme weather events continue to pose the greatest risk to the reliability and stability of the North American bulk power system, even though the system remains highly reliable and resilient, according to the latest assessment from the North American Electric Reliability Corporation.

NERC’s 2023 State of Reliability report also noted a disparity between the performance of the transmission and generation systems. The report found that transmission system reliability improved significantly for the fifth consecutive year and that the rate of protection system misoperations also continues to improve.

Conventional generation, however, was challenged by more frequent extreme weather and experienced its highest level of unavailability since NERC began gathering generator availability data in 2013.

The report found an increasing rate of outages for coal-fired generation over the observed five years, correlating with higher numbers of startups and maintenance outages. The unavailability of gas-fired generation in recent years also has been consistently higher during the winter months. Those were the two primary factors that conventional generation surpassed transmission in contributing to major load loss events, the report found. The report found no apparent trends in the unavailability of the other forms of generation.

The report analyzed past bulk power system reliability performance for the 2022 calendar year and, with additional findings arising in 2023, found that the performance of inverter-based resources must be improved if the bulk power system is to benefit from the rapid expansion of wind and solar power.

“Today’s BPS transmission system is continuing to show improvements in reliability and resilience, despite more common and extreme weather trends,” Donna Pratt, NERC’s performance analysis manager, said in a statement. “However, higher overall outage rates for coal and gas generation, as well as some utility-scale solar generation not operating as necessary for reliability, indicate that there is still significant work to be accomplished to accommodate the rapidly changing weather and generation resource mix in conjunction with electrification of the economy in a reliable manner,”

The SOR report also found that cyber security compromises and increased physical attacks on critical infrastructure in the latter part of 2022 point to a need to further develop and adapt reliability standards and guidelines.

The 2023 SOR included actions taken by NERC related to the findings and recommendations, including a Level 3 essential action alert for cold weather preparedness issued in in May 2023. Level 3 is NERC’s highest severity level classification, and it was the first time it was issued by the organization.

NERC also revised three standards as a result of the 2019 cold weather event. Those standards became effective April 1, 2022. Additional standards revisions resulting from the 2021 cold weather event are ongoing.

On March 14, 2023, NERC issued a Level 2 alert after multiple large-scale disturbances involving widespread loss of inverter-based resources resulted in abnormal performance across several bulk electric system solar photovoltaic generating resources.

In the SOR report, NERC recommended that the electric industry take immediate action to implement published guidelines and ensure the reliable operation of the bulk power system with increasing penetrations of inverter-based resources.

NERC also said that inverter-based resource modeling requirements need significant improvement to ensure that high-quality, accurate models are used during reliability studies so performance issues can be identified before they occur during real-time operations.