4/20/21 7:18 PM

W-A042021-01 Shift Factors Record Size Limitation Impacting SCED

NOTICE DATE: April 20, 2021

NOTICE TYPE: W-A042021-01 Operations

SHORT DESCRIPTION: Shift Factors Record Size Limitation Impacting SCED

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: April 1 to 20, 2021

LONG DESCRIPTION: ERCOT has discovered an issue in the Energy Management System (EMS) that impacted Security-Constrained Economic Dispatch (SCED) for Operating Days April 1 to 20, 2021. To address this issue, ERCOT will be deploying an emergency software update in production systems at 00:00 on April 21, 2021.

The issue occurred when the database for an application in EMS used to calculate Shift Factors reached its maximum record size. As a result, beginning with the April 1, 2021, Network Operations Model delivery (APR_ML1), Shift Factors for a small number of Resources were omitted from the list of Shift Factors passed from ERCOT’s Real-Time Contingency Analysis to SCED.  This omission affected all constraints activated since April 1, 2021.

Due to the omission of these Shift Factors, affected Generators were dispatched in SCED with the assumption of no impact to any active constraint. As a result, dispatch was potentially impacted for all SCED intervals during the affected time period, which potentially impacted Real-Time Market (RTM) prices. ERCOT Protocol Section 6.3(4) requires ERCOT to correct RTM prices when, among other reasons, (i) a Market solution is determined to be invalid, (ii) invalid prices are identified in an otherwise valid Market solution, or (iii) the Base Points received by Market Participants are inconsistent with the Base Points of a valid Market solution, unless accurate prices cannot be determined.  Although this issue potentially impacted RTM prices during the impacted SCED intervals, ERCOT cannot determine accurate prices because any effort to recalculate prices would require ERCOT to make significant assumptions concerning the operating behavior of individual Resources over extended periods of time. Therefore, ERCOT will not perform a price correction or seek review of prices for the impacted Operating Days by the ERCOT Board of Directors.

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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