NOTICE DATE:  August 14, 2009

NOTICE TYPE:  M-A081309-02   Operations

SHORT DESCRIPTION:  Provisional Approval of Modification to the Sandow Switch SPS (Oncor # 43)

INTENDED AUDIENCE:  ERCOT Market Participants

DAY AFFECTED:  August 14, 2009

LONG DESCRIPTION:  Oncor Electric Delivery has proposed a modification to the Special Protection System (SPS) at the Sandow Switch substation (Oncor SPS # 43). This SPS is intended to protect against post-contingency overloading on the Sandow – Taylor, Sandow – Elgin, and Elgin – Gilleland 138 kV Lines and the Sandow 345/138 kV Autotransformer that may occur under various conditions with the addition of Sandow unit # 5. The proposed modification is to raise the arming point of the SPS from 960 Amps to 1430 Amps for the Sandow – Taylor line due to recent transmission upgrades on this line.

ERCOT granted provisional approval of this SPS on August 13, 2009. The proposed changes indicated above have now been implemented in the field. Please note that the actual arming point was changed from 1430 Amps to 1428 Amps. Further details of the Sandow Switch SPS can be found in the “Special Protection Systems Information” section of the Planning and Operations Information secure website at the link below.

http://planning.ercot.com/login/login

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 e-mail at [log in to unmask].

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