The North American bulk power system remains "highly reliable" in the face of baseload retirements, growing penetration of renewable resources and continually evolving cyber and physical threats, an official with the North American Electric Reliability Corp. said Wednesday.
In fact, "by nearly every measure [for] reliability, 2018 was one of the most reliable years on record in the time we've been doing this report," John Moura, NERC's director of reliability assessment, said in a call with reporters after the release of the organization's annual state of reliability report.
For instance, frequency response performance -- considered a key measure of reliability for the bulk power system as it allows the grid to arrest and stabilize frequency deviations -- "improved significantly" in all four interconnections, Moura said. Further, the report said that misoperation rates for protection systems that prevent voltage and other reliability problems from propagating continued a "statistically significant downward and improving trend."
NERC's annual reliability report looks at grid performance over the prior year and analyzes industrywide trends in an effort to inform electricity companies, regulators and policymakers of emerging reliability risks and shed light on whether mitigation activities for known challenges are leading to system improvements.
IDENTIFYING SOLUTIONS
Despite concerns raised by the Trump administration, the retirement of baseload generation and influx of renewables has not created insurmountable reliability challenges.
Rather, "as more inverter-based resources [such as solar, wind and battery storage] are added, solutions to emerging reliability challenges are being identified," the report said.
NERC set up a task force in 2017 after discovering a reliability risk associated with inverter-based resource controls tripping and disconnecting from the bulk power system during routine transmission line outages, and in 2018 industry began implementing an inverter-based resource performance guideline.
"This, along with widespread recognition of the challenge, has gathered the industry's best technical experts to develop solutions to a variety of new protection and control requirements, clarifications to NERC reliability standards and technical specifications through the IEEE," Moura said.
Notably, the report found that coal-fired generation had "the highest forced-outage rate of all conventional fuels except during extreme winter weather when natural-gas-fired generation outages spikes above coal."
Moura added that the coal fleet's forced outage rate has been on a slight increasing trend over the past five years.
RECOMMENDATIONS
The report recommends continued attentiveness to the changing resource mix, with priority placed on understanding the implications of "frequency response under low inertia conditions; contributions of inverter-based resources to essential reliability services; increasing protection system and restoration complexities with increased inverter-based resources; and resource adequacy with increasing energy constraints."
The report also calls for the creation of metrics to gauge the "different dimensions" of resilience during the most extreme events, from withstanding the direct impact to managing through the event, recovering from it and preparing for the next one.
While 2018 did not have any cyber or physical incident that led to loss of load or unauthorized control actions, NERC still recommends improving threat information sharing and risk mitigation activities, including baking security measures into system design and practicing response and recovery procedures.
Among the report's other key findings was that extreme weather events continue to be the leading culprit of transmission, generation and load losses within NERC's territory, which encompasses the continental United States, most of Canada, and Baja California, Mexico.
TEXAS REMAINS RELIABILITY RISK
Also, NERC continues to view Texas as a reliability risk in 2019 as the state contends with a projected capacity deficit.
Better-than-expected performance by the state's generation fleet helped meet 2018 summer peak demand. Both wind and conventional generation in Texas saw higher-than-average peak availability during the summer season, allowing peak demand that hit a new record on July 19 to be served without the need for load shedding or other emergency operating procedures, the report said.
Moura noted that while conventional generation in the state made staffing and maintenance decisions and took other creative steps to prepare for the tight supply picture, on the wind side, "it just happened to be more windy than they planned for."
"That's a random event that happens. Next summer wind output could be very low for no other reason than the wind output wasn't correlated with peak demand," Moura said.
