NOTICE DATE:  December 11, 2012

NOTICE TYPE:  W-B121112-01 Operations

SHORT DESCRIPTION: Update to the West to North Generic transmission interface

INTENDED AUDIENCE:  ERCOT Market Participants

DAY AFFECTED:  December 31, 2012

LONG DESCRIPTION:  Beginning December 31, 2012, two new transmission lines associated with the West to North Stability Limit are expected to be energized. Energization of these new transmission lines may impact the value of the West to North Stability Limit utilized in the Day-Ahead Market, as well as the value calculated in the real-time Transient and Voltage Security Assessment Tools (TSAT and VSAT respectively), starting on Operating Day December 31, 2012.

ERCOT will also be implementing the new planning matrix (see attachment). Note that this Matrix is used for conditions when no thermal generators are in service and ERCOT uses TSAT and VSAT to calculate West to North Stability limits for conditions when thermal generation is in service. The interface definition for the West to North Stability Limit was modified to include these new transmission lines with the Network Operations Model, in preparation for these new lines coming into service with the understanding and expectation that the limit value would not be affected until these lines were energized.

ADDITIONAL INFORMATION:  A presentation was provided for the October 9, 2012, Congestion Management Working Group (CMWG) meeting and is available at http://www.ercot.com/content/meetings/cmwg/keydocs/2012/1009/ERCOT W_N update.ppt.

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].

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dh