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ERCOT Updates Minimum Operating Reserves for Emergency Conditions

The Electric Reliability Council of Texas on Nov. 1 announced an update to emergency operations reserve levels that it utilizes.

ERCOT has increased the minimum operating reserves requirements for emergency operations for each of its three Energy Emergency Alert (EEA) levels.

ERCOT periodically studies the level of online reserves that must be preserved to maintain system reliability even during emergency conditions. That level of reserves has increased as the resource mix has changed, with more wind, solar, and battery storage resources supplying power during emergency conditions, it said.

ERCOT will now require a baseline minimum operating reserve for EEA 3 of 1,500 MW, which automatically increases EEA 1 and EEA 2 reserve levels, as follows:

EEA 1 will occur if reserves reach 2,500 MW (previously 2,300 MW) and are not expected to recover within 30 minutes.

EEA 2 will occur if reserves reach 2,000 MW (previously 1,750 MW) and are not expected to recover within 30 minutes, or if frequency has dropped below 59.91 Hz for 15 minutes (previously 30 minutes).

EEA 3 will occur if reserves drop below 1,500 MW and are not expected to recover within 30 minutes, or if frequency drops below 59.8 Hz for any period of time. If either situation occurs, ERCOT would require Transmission and Distribution Service Providers to implement controlled outages, which impact residential, commercial, and industrial users.

Previously, an EEA 3 was issued when ERCOT’s operating reserves dropped below 1,430 MW. When operating reserves dropped below 1,000 MW, and were not expected to recover within 30 minutes, controlled outages were activated.

ERCOT has updated its Grid Conditions Page to align with these changes. More information on grid condition levels can be found at https://www.ercot.com/gridmktinfo/dashboards/gridconditions.

ERCOT said it will now issue a Watch to generators and other Market Participants, when operating reserves drop below 3,000 MW and are expected to remain below that level for 30 minutes.

ERCOT will also eliminate the Advisory notification that was previously issued to generators and other Market Participants when operating reserves dropped below 2,500 MW. 

ERCOT reviewed system inertia during the period of January 2019 through June 2022 in which operating reserves on the system were low (3,000 MW or less) and identified a minimum inertia value during this period of 200 GW-seconds.

ERCOT performed simulations of the loss of the largest single unit contingency with 200 GW-seconds of system inertia and found that the system must maintain 1,500 MW of operating reserves to avoid potential Under-Frequency Load Shedding (UFLS) activation.

Inertia refers to the kinetic energy stored in large rotating generators in conventional generation Resources. System inertia resists changes to system frequency that occurs when a generator-to-load imbalance occurs.

Inverter-based resources (wind, solar, and battery storage) do not have rotational inertia, ERCOT noted.

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