operations;settlements

1/21/19 4:35 PM

M-A012119-01 Error detected in certain Mitigated Offer Cap calculations


NOTICE DATE:  January 21, 2019

NOTICE TYPE:  M-A012119-01 Settlements

SHORT DESCRIPTION:  Error detected in certain Mitigated Offer Cap calculations

INTENDED AUDIENCE:  ERCOT Market Participants

DAYS AFFECTED:  Certain Operating Days in August and October 2017, February, May and December 2018

LONG DESCRIPTION:  ERCOT has identified an error in how Mitigated Offer Caps (MOCs) were calculated for certain Operating Days (ODs) over five months in 2017 and 2018.  During months in which ERCOT made mid-month updates to Verifiable Costs, ERCOT’s Settlements system incorrectly doubled or tripled the value of Operations and Maintenance (O&M) costs above the Low Sustained Limit (LSL) for certain Resources with Verifiable Costs. As a result, these Resources were under-mitigated in affected Security-Constrained Economic Dispatch (SCED) intervals. MOC components other than O&M were not impacted. O&M costs used for startup and Minimum-Energy Offer Caps, and for Reliability Unit Commitment and Day-Ahead Make-Whole Payments, were likewise not impacted.

ERCOT has determined that the error impacted the following Operating Days:

August 2, 2017 – August 31, 2017;

October 4, 2017 – October 31, 2017;

February 14, 2018 – February 28, 2018;

May 2, 2018 – May 31, 2018; and

December 5, 2018 – December 31, 2018.

 

Although this issue may have affected prices, and dispatch to some extent, ERCOT is unable to perform price corrections because it cannot determine accurate prices, as any effort to recalculate new prices would require ERCOT to make significant assumptions concerning the operating behavior of individual Resources.

Pending implementation of updates to impacted production systems, ERCOT has instituted manual processes to correct the error going forward.  Production system fixes are expected to be implemented during the release scheduled for April 2 - 4, 2019.

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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