NOTICE DATE: December 5, 2025

NOTICE TYPE: M-B120525-01 Operations

SHORT DESCRIPTION: Real-Time Market Price Correction - Generic Transmission Constraint incorrectly considered in SCED

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: November 20, 2025

LONG DESCRIPTION: On Operating Day (OD) November 20, 2025, a post-contingency overload on a Generic Transmission Constraint (GTC) was activated from 15:50 to 16:50, which impacted the results of Security-Constrained Economic Dispatch (SCED). Within this time frame, the constraint incurred non-zero shadow prices during multiple SCED intervals.

The root cause was determined to be an edge case scenario wherein the base case flow of the constraint was extremely low, which inadvertently caused the post-contingency flow on the GTC to exceed a tolerance parameter and resulted in the GTC being incorrectly deemed eligible for activation and passed to SCED.

Upon completion of an impact analysis, ERCOT determined that the impact to prices met the significance criteria in ERCOT Protocol 6.3, Adjustment Period and Real-Time Operations Timeline, for pursuing a price correction for OD November 20, 2025. ERCOT corrected prices for this OD before the deadline of November 24, 2025 at 4:00PM.

Price Correction files for OD November 20, 2025 have been posted on the Market Information System (MIS).

CONTACT: If you have any questions, please contact your ERCOT Account Manager. You may also call the general ERCOT Client Services phone number at (512) 248-3900 or contact ERCOT Client Services via email at ClientServices@ercot.com.

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dg