NOTICE DATE: October 1, 2019

NOTICE TYPE: M-A100119-01 Settlements

SHORT DESCRIPTION: Issue Affecting Real-Time Ancillary Service Imbalance Payment or Charge

INTENDED AUDIENCE: Market Participant Settlement personnel

DAYS AFFECTED: June 1, 2014 to September 17, 2019

LONG DESCRIPTION: ERCOT has discovered an issue affecting the calculation of the Real-Time Ancillary Service Imbalance Payment or Charge. Pursuant to Protocol Section 6.7.5(2), the Real-Time Ancillary Service Imbalance Payment or Charge is calculated based on the amount of On-Line capacity and metered Generation for each QSE. Per Protocol Section 6.7.5(3)(d), when the telemetered Generation for a Resource is less than 95% of the telemetered Low Sustained Limit, the Resource is excluded from the amount of On-Line capacity and metered Generation used to calculate the payment or charge. Whether a Resource is excluded is determined by Settlement Interval in the settlement system using 15-minute data. ERCOT recently discovered, however, that logic in the Energy Management System (EMS) has also been evaluating this exclusion every four seconds to calculate the Real-Time On-Line High Sustained Limit (RTOLHSL) for each Settlement Interval. In certain cases, this double application of the exclusion impacted calculation of the Ancillary Service Imbalance Payment or Charge by improperly lowering the amount of a QSE's On-Line capacity used to calculate the payment or charge.

This issue has been in place since the implementation of the Real-Time Ancillary Service Imbalance Payment or Charge on June 1, 2014. An emergency code fix was implemented on September 17, 2019 in EMS to correct this issue by removing the application of the exclusion from the calculation of RTOLHSL in EMS. 

To the extent this issue resulted in an incorrect calculation of the Ancillary Service Imbalance Payment or Charge prior to implementation of the code fix, corrections for affected Operating Days from April 1, 2019 to September 17, 2019 will be reflected in applicable Real-Time Market (RTM) Final and True-Up Settlement Statements. In addition, all Operating Days before April 1, 2019 have been evaluated for resettlement and ERCOT has determined that Operating Days August 15, 2018 and September 17, 2018 require resettlement pursuant to Protocol Section 9.5.6(2).  ERCOT will issue Resettlement Statements for these impacted Operating Days on October 10, 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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