March 6, 2008 Technical Advisory Committee Luminant Energy & Oncor Tyler Grande Autotransformer Addition and 138 kV Line Upgrade Project Jay Teixeira Manager, Regional Planning

2 Technical Advisory Committee March 6, 2008 Description of Recommendation ReconductorRebuild Use a spare 345/138 kV auto at the Tyler Grande Switching Station (Southeast) Cost: $3,665,000 Install 4-ohm 138 kV switchable series reactors on the Tyler Grande autotransformer Cost: $1,500,000 Rebuild the Tyler Grande – Tyler South 138 kV line so that the Rate B is 326 MVA. The circuit will be rebuilt for double circuit operation with one circuit being the circuit from Tyler Grande – Tyler Elkton and the other circuit being a radial feed to Tyler South. Cost: $2,750,000 Upgrade the Tyler Northeast – Tyler East 138 kV line so that the Rate B is 326 MVA Cost: $1,900,000 Upgrade the Tyler GE – Tyler Omen Road 138 kV line so that the Rate B is 326 MVA Cost: $1,300,000 TOTAL COST: $11,115,000

3 Technical Advisory CommitteeMarch 6, 2008 Project Need - Reliability Analysis The Tyler area is served by two 345/138 kV autotransformers at Shamburger and Elkton. Several contingencies cause low voltage problems. Analysis showed unserved energy caused by overloads on two 138 kV lines and the Elkton 345/138 kV autotransformer. Two approaches were used to eliminate the unserved energy. –Upgrade overloaded lines/transformers (Direct) –Use part of proposed project (Indirect)

4 Technical Advisory CommitteeMarch 6, 2008 Project Need - Reliability Analysis Continued Direct Method to eliminate the unserved energy. Indirect Method - Using parts of the proposed project to eliminate the unserved energy. Capital cost of Indirect Method significantly lower Add a second Elkton 345/138 kV 600 MVA autotransformer$11,165,000 Upgrade the Elkton – Tyler West 138 kV line$ 3,670,000 Upgrade the Elkton – Tyler Bullard 138 kV line$ 1,718,000 Total Cost$16,553,000 Addition of the 345/138 kV autotransformer using a spare 493 MVA autotransformer $ 3,665,000 Rebuild of the Tyler Grande – Tyler South 138 kV line$ 2,750,000 Total Cost$ 6,415,000

5 Technical Advisory CommitteeMarch 6, 2008 Project Need - Economic Analysis The remaining proposed projects were analyzed to see if they meet ERCOT’s economic criteria. The upgrade of the Tyler Northeast to Tyler East and Tyler GE to Tyler Omen Road 138 kV lines and the addition of the 138 kV series reactors on the Tyler Grande autotransformer proved to be the most economic set of projects providing production cost savings of $37,960,000 from 2009 through UpgradeCapital Cost ( $M ) Incremental Savings ( $M ) Total Savings Tyler Northeast - Tyler East 138 kV line & 138 kV Switchable Series Reactors at Tyler Grande & Tyler GE - Tyler Omen Road 138 kV line

6 Technical Advisory CommitteeMarch 6, 2008 Stakeholder Review The Stakeholder review period for this project was held in September 2007 There were no dissenting comments on this package and Oncor & Luminant resolved all questions Scheduled in-service prior to Summer 2009

7 Technical Advisory CommitteeMarch 6, 2008 ERCOT Support for the Project Reliability Justified Projects –Addition of the 345/138 kV autotransformer using a spare 493 MVA autotransformer –Rebuild of the Tyler Grande – Tyler South 138 kV line so that the Rate B is 326 MVA Economically Justified Projects –Upgrade the Tyler Northeast to Tyler East 138 kV line so that the Rate B is 326 MVA –Upgrade the Tyler GE to Tyler Omen Road 138 kV line so that the Rate B is 326 MVA –Addition of the 138 kV series reactors on the Tyler Grande autotransformer ERCOT will be requesting that the projects be endorsed by the ERCOT Board Of Directors.

Questions?