1. December 14, 2007 RPG - CREZ Meeting CREZ Transmission Optimization Study: Update Warren Lasher ERCOT System Assessment

2. 2 RPG - CREZ Meeting December 14, 2007 Designated Zones and Scenario Wind Levels Capacity of New CREZ Wind by Scenario (MW) Wind Zone Scen. 1 Scen. 2 Scen. 3 Scen. 4 Panhandle A 1,4223,1914,9606,660 Panhandle B 1,0672,3933,7200 McCamey8291,8592,8903,190 Central1,3583,0474,7355,615 Central West 4741,0631,6512,051 Total * 12,05318,45624,85924,419 * Assumes 6,903 MW of existing wind capacity

3. 3 RPG - CREZ Meeting December 14, 2007 Overview of Power Flows – Scenario 2 DFW SA There are limitations on how much generation any one load center can absorb. Too much power flow being directed to DFW can cause significant planning challenges. 5,600 MW2,600 MW10,300 MW HGA

4. 4 RPG - CREZ Meeting December 14, 2007 Overview of Alternate Power Flows HGA DFW SA One possible solution is to direct all power flows towards the southeast

5. 5 RPG - CREZ Meeting December 14, 2007 Overview of Alternate Power Flows HGA DFW SA An alternative solution is to create a significant pathway through the core of ERCOT (shown in red)

6. 6 RPG - CREZ Meeting December 14, 2007 Game Plan ERCOT Planning is evaluating several different general concepts for transporting wind from CREZ generation to load centers. Initial analysis has been conducted using Scenario 2 because this level of wind can be modeled in steady-state power flow models and in SCUC economic dispatch model. We will be evaluating the differential performance of the solutions that are developed. Some solutions may be better suited to higher or lower scenarios. Our intent is to develop each of these solutions to the point that each can be compared from an economic, steady-state, and transient stability context. Final solution for each scenario may contain aspects of several of these conceptual designs.

7. 7 RPG - CREZ Meeting December 14, 2007 Solutions being considered include the following: 1)Reconductoring existing circuits 2)Incremental 345-kV solution 3)Reduced number of right-of-ways using higher voltage circuits (500 kV and 765 kV) 4)Low Impedance Backbone for Wind Connections 5)Low Impedance loop circuits (around load centers and/or around wind generation zones) 6)HVDC Circuit(s) to move wind generation to load centers or to move power between load centers 7)Development of 2 west Texas transmission systems Solutions

8. 8 RPG - CREZ Meeting December 14, 2007 Solutions being considered include the following: 2)Incremental 345-kV solution 4)Low Impedance Backbone for Wind Connections Solutions Advantages: 1)Congestion between load centers in ERCOT is reduced (overall system benefit) 2)Increased flexibility of connecting additional circuits from CREZ generation to load – connect to nearest portion of backbone circuit Disadvantages: 1)Cost of low-impedance backbone 2)Use of low-impedance backbone may require upgrades of underlying transmission system in some areas Advantages: 1)Networked solution will lead to flexibility for generation siting 2)New ROWs can be used to alleviate congestion on underlying circuits Disadvantages: 1)May lead to solution with numerous new ROWs 2)May not provide much transmission expansion capacity 3)A sufficient number of suitable connection points to load centers will need to be identified

9. Questions or Comments?

10. 10 RPG - CREZ Meeting December 14, 2007 HVDC Economic Modeling There are two options for modeling HVDC lines in UPlan 1)Place a load at one end of the line, and a generator at the other end. Give each an predefined hourly pattern to reflect flows on the DC line. User can define power flows to match wind levels or to match operational limitations User can model losses on the line 2)Use the automatic modeling of a HVDC line in UPlan User defines the end points of the HVDC line and specifies the line rating UPlan will model the HVDC line as though there were loads and generators at each line terminus

11. 11 RPG - CREZ Meeting December 14, 2007 UPlan HVDC Modeling Output of Generator A will equal load A Output of Generator B will equal load B If Gen A ≠ 0 then Gen B = 0 and vice versa Gen A and Gen B have zero cost; max output equals rating of line Cost to serve loads A and B are defined by LMP algorithm UPlan will select the output of Gen A (or Gen B) in every hour to minimize total production cost A A B B

12. 12 RPG - CREZ Meeting December 14, 2007 Other Issues 1)Distribution of models 2)Volunteers for evaluating or developing plans 1)138 kV limiting pathways 2)Overall plans 3)Request for Project Locations 4)GE Wind Impact Study 5)Other RPG Issues Feel free to contact me with questions or comments: wlasher@ercot.com or 512-248-6379. wlasher@ercot.com