A more than 5,000-MW generation shortfall in Texas has pushed the Electric Reliability Council of Texas' projected 2018 summer reserve margins below recommended levels, warned a new report by North America's electricity grid reliability organization. The report also found that constraints at the Aliso Canyon natural gas storage facility in Los Angeles County has raised reliability concerns for California ISO as well.
The North American Electric Reliability Corp.'s 2018 Summer Reliability Assessment released May 30 said the anticipated summer reserve margin for Texas is 10.9%, which is well below ERCOT's 13.75% reference margin level and roughly 4% lower than its 2017 summer projection.
NERC found that all other reliability regions will meet their reference margin levels.
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In a presentation, Thomas Coleman, NERC's director of reliability assessments, blamed retirements of 4.3 GW of coal-fired power plants within the past year and delays in bringing 2 GW of new generation online for driving ERCOT's reserve margin from 18.9% in May 2017 down to 9.3% in December 2017. Even though other factors have boosted capacity in ERCOT since then, the region's preseason planning reserve still is projected to be just 10.9%, he explained.
Furthermore, NERC said an operational risk assessment showed that ERCOT's expected reserve margin level drops further to roughly negative 5% under scenarios considering various combinations of planned and forced outages, low wind generation and extreme weather, such as an extended heat wave, that increase the risk of load shedding.
"But any single one of those events would actually drop us below [ERCOT's] operating reserve margin of 2,300 MW," Coleman said. Texas' grid operator "would [then] be in an energy emergency alert level one. That would require the need for measures such as demand response or providing incentives for additional efficiency out there so that those reserve margins could be met."
NERC said ERCOT plans to address any potential shortfall by seeking voluntary load reductions from utilities if needed to maintain grid reliability. Roughly 2,100 MW of additional generation under development in the region will not be available until after the summer, according to NERC.
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In California, NERC said, operational constraints that limit natural gas output at Southern California Gas Co.'s underground Aliso Canyon storage facility, which has been under restrictions since a multimonth leak began in late 2015, continues to affect the availability of natural gas for power plants in Southern California. Below-normal hydro generation projected for the summer further exacerbates the potential reliability concern for CAISO, NERC said.
Additionally, NERC said the need for fast-ramping gas generation and other flexible resources across California presents a reliability challenge for CAISO during summer 2018 due to the state's high penetration of renewables.
"Grid operators in California and across North America are increasingly looking to fast-ramping gas units and other flexible generation capacity to keep the bulk power system reliable because the output from wind and solar, both utility-scale and behind-the-meter, can change frequently and sometimes unexpectedly," Coleman said in a news release.
In May 2017, CAISO issued its first stage-one emergency in 10 years. The following October, during some of the worst and deadliest wildfires in the state's history, CAISO issued a stage-three energy emergency alert that activated demand response measures but stopped short of load shedding.


