Released in late June, the North American Electric Reliability Corporation’s (NERC’s) “2024 State of Reliability” report found that the bulk power system (BPS) remained reliable and resilient in 2023, with no firm load shedding during energy emergencies, and quick recovery following severe storms in the United States and wildfires in Canada.

“Although the BPS was extremely successful at providing reliable energy, high generator outage trends and ongoing inverter ride-through challenges signal potential risks that require mitigating action,” said the report.

“Last year, we saw relatively mild weather coupled with enhanced preparation measures, which lessened the stressors that system operators were faced with during the summer and winter peak periods,” said John Moura, director, Reliability Assessment and Performance Analysis for NERC. “The combination of the transforming resource mix, rising forced outage rates for coal generation, and issues with reserve margins are shifting the riskiest periods to spring and fall shoulder months.”

The report went on to add that, with no major winter events, the forced outage rates for coal generation fell to 12 percent in 2023, compared to 13.9 percent in 2022, but continue a long-term upward trend when compared to the average annual outage rate between 2014-2022,which was 10.2 percent.

Conversely, transmission outage severity saw its first increase, reaching 173.8 in 2023, up from an all-time low of 161.6 in 2022, and slightly above the prior four years’ average of 170.9. “This increase is a direct result of the record-setting Canadian wildfires. Excluding these, the metric falls to an all-time low of 143.2,” said the report.

The report also noted that response by inverter-based resources to system disturbances continues to impact many solar facilities, with ride-through issues being observed at large battery storage and wind plants.

“These events are a clear indication that this issue can be greatly alleviated, if not resolved, by plant owners working more closely with manufacturers,” said Jack Norris, engineer, Performance Analysis, for NERC. “Until fixes are implemented, the risk posed by this issue continues to grow as inverter-based resources continue to rapidly increase.”

The report, which is a look back at system performance over 2023, identified system performance trends and emerging reliability risks; reported on the relative health of the interconnected system; and measured the success of mitigation activities deployed.

Key 2023 findings included improved performance in the Texas Interconnection, due to the use of battery energy storage systems to support a balanced frequency and a significantly improved mis-operation rate when compared to the preceding four years. “However, new challenges were also identified due to an increasing dependence on variable resources,” said the report.

(The 2024 State of Reliability Overview and 2024 State of Reliability Technical Assessment provide objective and concise information for policymakers and industry leaders on issues that affect the reliability and resilience of the North American BPS, while providing strong technical support for those interested in the underlying data and detailed analytics.)