NOTICE DATE:  February 16, 2012

NOTICE TYPE:  W-A020812-02 Operations

SHORT DESCRIPTION:  Reverting back to the Spreadsheet for the West to North Stability Limits

INTENDED AUDIENCE:  ERCOT Market Participants

DAY AFFECTED:  February 16, 2012

LONG DESCRIPTION:  ERCOT began using the TSAT tool to calculate the West to North Stability limits in real-time on February 15, 2012. The TSAT tool operated as expected.  However, during real-time operations ERCOT identified issues within the Energy Management System's Real-Time Contingency Analysis which restricted the limit to a value lower than TSAT value.  ERCOT is working to resolve this issue, but until this is resolved ERCOT has reverted back to using the lower West to North Stability limits spreadsheet.  This action is being taken for both Day Ahead and Real-Time so that the tools used in both timeframes are consistent.  ERCOT will issue a notice prior to using the TSAT tool for day ahead and real-time limits again.

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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