A large swath of the North American bulk power system faces either a high or elevated potential this summer for insufficient operating reserves under normal operating conditions. Regions include MISO, ERCOT, SPP, all of WECC in the United States and MRO SaskPower in Canada.
The summer outlook, which was presented by the North American Electric Reliability Corp. (NERC) on May 18, bathed much of North America either in orange for elevated risk or red for high risk. The map represented “one of our most cautionary tales” in recent years, said John Moura, director of reliability assessments for the Atlanta-based organization that aims to assure the bulk power system’s reliability.
The 2022 summer assessment said that the Midcontinent ISO faces a capacity shortfall in its North and Central areas, resulting in what NERC called a “high risk of energy emergencies during peak summer conditions.”
MISO is a concern
NERC said in its summer assessment that peak demand projections in MISO have increased by 1.7% since last summer due in part to a return to normal demand patterns that had been altered in prior years by the pandemic. It said that a more impactful change was that the region will have 3,200 MW (2.3%) less generation capacity than in the summer of 2021.
As a result, NERC warned that system operators in MISO “are more likely” to need operating mitigations, such as load modifying resources or non-firm imports, to meet reserve requirements under normal peak summer conditions.
Further complicating the outlook, NERC said that at the start of the summer, a key transmission line connecting MISO’s northern and southern areas will be out of service. The transmission outage affects 1,000 MW of firm transfers between the Midwestern and Southern MISO system that includes parts of Arkansas, Louisiana, and Mississippi. The four-mile section of line, which was damaged in December, is expected to be restored at the end of June.
NERC also warned that drought conditions create “heightened reliability risk” for the summer. It said that energy output from hydro generators throughout most of the Western United States is being affected by widespread drought and below-normal snowpack. Dry hydrological conditions threaten the availability of hydroelectricity for transfers throughout the Western Interconnection.
Some assessment areas, including WECC’s California-Mexico (CA/MX) and Southwest Reserve Sharing Group (SRSG), depend on substantial electricity imports to meet demand on hot summer evenings and other times when variable energy resource output is diminishing.
As a result, on the event of wide-area extreme heat event, “all U.S. assessment areas in the Western Interconnection are at risk of energy emergencies due to the limited supply of electricity available for transfer,” the assessment said.
Texas drought conditions
What’s more, extreme drought across much of Texas this summer may produce weather conditions that are “favorable to prolonged, wide-area heat events and extreme peak electricity demand,” the assessment said. It said that resource additions to the ERCOT system in recent years—predominantly solar and some wind—have raised Anticipated Reserve Margins above Reference Margin Levels and ease concerns of capacity shortfalls for normal peak demand.
However, extreme heat increases peak demand and can be accompanied by weather patterns that lead to increased forced outages or reduced energy output from resources of all types. “A combination of extreme peak demand, low wind, and high outage rates from thermal generators could require system operators to use emergency procedures, up to and including temporary manual load shedding,” the report said.
As drought conditions continue over the Missouri River Basin, output from thermal generators that use the Missouri River for cooling in Southwest Power Pool (SPP) may be affected in summer months. Low water levels in the river can impact generators with once-through cooling and lead to reduced output capacity. Energy output from hydro generators on the river can also be affected by drought conservation measures implemented in the reservoir system. Outages and reduced output from thermal and hydro generation could lead to energy shortfalls at peak demand. Although periods of above normal wind generator output “may give some relief”, the report cautioned that “this energy is not assured.” System operators could require emergency procedures to meet peak demand during periods of high generator unavailability.
NERC flagged several other concerns that may impact reliability through the summer.
Supply chain issues and commissioning challenges on new resource and transmission projects are a concern in areas where completion is needed for reliability during summer peak periods. It said that WECC-CA/MX, and WECC-SRSG have sizeable amounts of generation capacity in development and included in their resource projections for summer. In ERCOT, transmission expansion projects are underway to alleviate transmission constraints and maintain system stability as the bulk power system is adapted to rapid growth in new generation. NERC warned that delays or cancellations of transmission projects can cause transmission system congestion during peak conditions and affect the ability to serve load in localized areas.
Coal-fired generators are having difficulty obtaining fuel and non-fuel consumables as supply chains are stressed. No specific reliability impacts are currently foreseen by NERC. However, coal stockpiles at power plants are relatively low compared to historical levels. Some owners and operators report challenges in arranging replenishment due to mine closures, rail shipping limitations, and increased coal exports.
The electricity and other critical infrastructure sectors face cyber security threats from Russia and other potential actors amid heightened geopolitical tensions in addition to ongoing cyber risks. Russian attackers may be planning or attempting malicious cyber activity to gain access and disrupt the electric grid in North America in retaliation for support to Ukraine.
Unexpected tripping of solar photovoltaic (PV) resources during grid disturbances continues to be a reliability concern. In May and June 2021, the Texas Interconnection experienced widespread solar PV loss events like those previously observed in the California area. Similarly, four additional solar PV loss events occurred between June and August 2021 in California.
During these events, widespread loss of solar PV resources was also coupled with the loss of synchronous generation, unintended interactions with remedial action schemes, and some tripping of distributed energy resources. NERC said that as industry “urgently takes steps to address systemic reliability issues” through modeling, planning, and interconnection processes, system operators in areas with significant amounts of solar PV resources should be aware of the potential for resource loss events during grid disturbances.
And if that wasn’t enough, the NERC report warned that an active late-summer wildfire season in the Western United States and Canada is anticipated, posing still more reliability risks.
