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NOTICE DATE:  January 11, 2019



NOTICE TYPE:  W-A011119-01 Operations



SHORT DESCRIPTION:  Update to the SCED Limit Calculation



INTENDED AUDIENCE:  ERCOT Market Participants



DAY AFFECTED:  February 5 - 7, 2019



LONG DESCRIPTION:  ERCOT will implement System Change Request (SCR) 794, Update SCED Limit Calculation ERCOT, on February 5 - 7, 2018. This SCR changes the methodology in which the Security-Constrained Economic Dispatch (SCED) limit is calculated by the Transmission Constraint Manager (TCM) to convert the Megavolt Ampere (MVA) limit for a transmission element into a Megawatt (MW) limit that can be used by SCED for determining Resource dispatch and prices.



The current methodology uses the following equation which has been problematic as the MW flow approaches zero:







The new methodology will use the following logic and equations to address the issue:









ADDITIONAL INFORMATION:  SCR794<http://www.ercot.com/mktrules/issues/SCR794#summary> and associated documents can be found on the ERCOT website.

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]<mailto:[log in to unmask]>.



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