NOTICE DATE: November 14, 2019

NOTICE TYPE: M-A102419-02 Operations

SHORT DESCRIPTION: Update: Potential Price Correction – Incorrect Electrical Bus Shift Factors in the Real-Time Market

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: October 23 – 24, 26, & 29 – 31, 2019 and November 4 & 6, 2019

LONG DESCRIPTION: During its review of the Real-Time market (RTM) incorrect Electrical Bus Shift Factor issue described in Market Notice M-A102419-01, ERCOT identified a separate, but related software error. ERCOT has determined that for Operating Days (ODs) 10/16/2019 – 11/07/2019, the software intended to capture the list of Electrical Buses that are fully disconnected from the rest of the ERCOT grid under a contingency, also included Electrical Buses that are on the end of open-ended transmission equipment under contingency. Upon identification of this software error, ERCOT implemented an emergency fix and began investigating prices for ODs 10/16/2019 – 11/07/2019.

For ODs 10/16/2019 – 10/21/2019, ERCOT has determined that there were no pricing impacts beyond that which were identified in the related price correction issue (see Market Notice M-A102419-01). Moreover, for ODs 10/22/2019, 10/25/2019, 10/27/2019 – 10/28/2019, 11/01/2019 – 11/03/2019, 11/05/2019, and 11/07/2019, ERCOT has determined that there were no pricing impacts. Accordingly, ERCOT will not be recommending review of these ODs by the ERCOT Board of Directors (Board) at its December meeting.

For ODs 10/23/2019 – 10/24/2019, 10/26/2019, 10/29/2019 – 10/31/2019, 11/04/2019, and 11/06/2019, ERCOT has determined that this newly identified issue had some impact on certain Real-Time Settlement Point Prices (RTSPPs) and Real-Time Price for Energy Metered for Resources (RTRMPRs). Therefore, ERCOT will seek ERCOT Board review of RTM prices for these affected ODs at the December 2019 ERCOT Board meeting.

ADDITIONAL INFORMATION: Supporting documents and re-calculated prices will be included in materials for the December 2019 ERCOT Board meeting.

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].

If you are receiving email from a public ERCOT distribution list that you no longer wish to receive, please follow this link in order to unsubscribe from this list: http://lists.ercot.com.

NOTICE DATE: October 24, 2019

NOTICE TYPE: M-A102419-01 Operations

SHORT DESCRIPTION: Potential Price Correction – Incorrect Electrical Bus Shift Factors in the Real-Time Market

INTENDED AUDIENCE: All Market Participants

DAYS AFFECTED: October 16 – 21, 2019

LONG DESCRIPTION: On October 21, 2019, ERCOT became aware of a software error that occurred during a recent update to ERCOT’s Energy and Market Management System (EMMS). On October 16, 2019, ERCOT deployed a system enhancement for the calculation of Electrical Bus Shift Factors for active constraints in the Real-Time Market (RTM).

The system enhancement was intended to set the Shift Factor of an Electrical Bus for a single constraint to “0” if the contingency related to the constraint disconnects the Electrical Bus. However, following the system enhancement, where an active contingency disconnected an Electrical Bus, all Shift Factors associated with that Electrical Bus were incorrectly set to “0.” As a result, the Shift Factors for some Electrical Buses were incorrectly set to “0” and used in the calculations for certain Real-Time Settlement Point Prices (RTSPPs) and Real-Time Price for Energy Metered for Resources (RTRMPRs). Because Security-Constrained Economic Dispatch (SCED) uses Resource Shift Factors rather than Electrical Bus Shift Factors in its dispatch optimization, Resource Base Points were unaffected by this error.

Upon identification of the software error, ERCOT immediately implemented an emergency fix and began investigating RTM prices for Operating Days (ODs) October 16 - 21, 2019. ERCOT has determined that this issue impacted certain RTSPPs and RTRMPRs for ODs October 16 – 21, 2019.

ERCOT corrected RTM prices for OD October 21, 2019, in accordance with ERCOT Protocol Section 6.3(5).

ERCOT will seek ERCOT Board review of RTM prices for ODs October 16 – 20, 2019, at the December 2019 ERCOT Board meeting.

ADDITIONAL INFORMATION: Supporting documents and re-calculated prices will be included in materials for the December 2019 ERCOT Board meeting.

If you are receiving email from a public ERCOT distribution list that you no longer wish to receive, please follow this link in order to unsubscribe from this list: http://lists.ercot.com.