NOTICE DATE: September 8, 2023

NOTICE TYPE: M-B090823-01 Settlements

SHORT DESCRIPTION: Software errors identified in Settlement System

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: October 15, 2022 through August 30, 2023

LONG DESCRIPTION:  ERCOT has identified software errors introduced with the implementation of NPRR863, Creation of ERCOT Contingency Reserve Service and Revisions to Responsive Reserve. These errors impact the billing determinants used in Real-Time Ancillary Service Imbalance Payments and Charges and Reliability Unit Commitment (RUC) Capacity Shortfall Settlement.  

The first issue is related to the billing determinant for Ancillary Service Resource Responsibility Capacity for Responsive Reserve at Snapshot (HRRSNAP) and the billing determinant for Resource Operation Status at Snapshot (STATUSSNAP) used in RUC Capacity Shortfall Settlement. Both the HRRSNAP and STATUSSNAP billing determinants utilize data from both the previous Operating Day and the current Operating Day to create the data used in the current Operating Day’s Settlements. However, for both of these billing determinants, it was discovered that the Settlement System was incorrectly only utilizing the current Operating Day’s data in the creation of HRRSNAP and STATUSSNAP for RUC Capacity Shortfall Settlement.

The HRRSNAP issue was first introduced with the Fast Frequency Response (FFR) Advancement project (phase 2 of NPRR863) on October 15, 2022. The STATUSSNAP issue was introduced with phase 3 of the ECRS project on June 9, 2023.

ERCOT has implemented the software corrections on Operating Day June 10, 2023 and June 15, 2023, for the HRRSNAP and STATUSSNAP errors, respectively. Data for HRRSNAP for the impacted Operating Days after December 23, 2022 were corrected before the next scheduled Settlement run.  An analysis was conducted on the twelve impacted Operating Days between October 15, 2022, and December 22, 2022 that were past True-Up Settlement. It was determined that none of the impacted Operating Days met the resettlement threshold as specified in paragraph (2) of Protocol Section 9.5.6, RTM Resettlement Statement. Data for STATUSSNAP for Operating Days June 9, 2023 through June 14, 2023 were corrected on the Final Settlement.

The second issue was introduced in the Settlement System on June 8, 2023 with the implementation of phase 3 of the ECRS project. This error shifted the assigned settlement interval one interval later (i.e. Interval 2 should be Interval 1). This error is limited to CLR and NCLR data values used in the calculation of Real-Time Ancillary Service Imbalance Payments and Charges. 

ERCOT has implemented a software correction as of Operating Day August 31, 2023. Data for impacted Operating Days prior to August 31, 2023 will be corrected before the next scheduled Settlement run.

The impacted billing determinants for this issue are listed below:

Billing Determinant



Real-Time Low Power Consumption for the Controllable Load Resource


Real-Time Net Power Consumption from the Controllable Load Resource


Real-Time Non-Spin Schedule for the Controllable Load Resource


Real-Time Controllable Load Resource Non-Spin Responsibility


Real-Time Non-Controllable Load Resource ERCOT Contingency Reserve


Real-Time Non-Controllable Load Resource Low Power Consumption


Real-Time Non-Controllable Load Resource Net Power Consumption


Real-Time Non-Spin Schedule for the Non-Controllable Load Resource


Real-Time Non-Controllable Load Resource Non-Spin Responsibility


Real-Time Non-Controllable Load Resource Responsive Reserve


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 [log in to unmask].

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