February 17, 2012 Regional Planning Group CREZ Shunt Switching John Adams Principal Engineer

2 RPG Outline Review of Section 14 of the ABB CREZ Reactive Study –Purpose = check breaker duty cycles and confirm bank sizes –Full-year 8760 hour chronological analysis –Intra-hour chronological analysis for maximum variability

3 Methodology Based on 2009 operating data of existing windfarms in CREZ areas Scaled up from 1269 MW nameplate (representative windfarms) to MW nameplate, “Initial Build” level, per area profile Variation in wind generation offset by non- wind generation in the east No contingencies applied RPG

4 Reactive Assumptions Var limits of future CREZ windfarms were reduced to preserve reactive capabilities for disturbances All switchable shunts were enabled CREZ switchable shunts were set to control their own bus voltages, +/- 2% except where the TSPs requested different ranges CREZ SVCs not modeled, also to preserve reactive capabilities for disturbances RPG

5 Full-Year Results Proposed reactor banks sizes were reduced at Hereford and at Edison substations to reduce the bus voltage change per switching operation Total number of switch operations per CREZ reactive bank for the year varied from very few to 700. RPG

6 Full-Year Results Analysis repeated with the Oklaunion plant brought on-line –Drastically reduced the total number of switch operations per bank at Hereford, Oklaunion, and Riley Analysis repeated for wind dispatch biased towards new CREZ generators and away from existing windfarms –Almost no change from base analysis RPG

7 Intra-hour Results, Sample Hour RPG

8 Intra-hour Results, Wind Ramp Down On April 30, 2009, from 21:30 to 22:30 total ERCOT load decreased 3131 MW, about 8% From 21:47 to 22:16, total ERCOT wind generation decreased 2437 MW, about 53% The simulation for this sample hour produced 25 individual switch operations RPG

9 Intra-Hour Results, Wind Ramp Down Riley, 5 switch operations from to 0 to -50 to -100 to -150 to -200 Mvar Hereford, 3 switch operations from -100 to -150 to -200 to -150 Mvar Clear Crossing, 2 switch operations from -200 to -250 to -300 Mvar RPG

10 Intra-Hour Results, Wind Ramp Down Red Creek, 2 switch operations from 0 to -100 to 0 Mvar Brown, 2 switch operations from +100 to 0 to -100 Mvar Edison1 and Edison2, 2 switch operations each from 0 to -50 to -100 Mvar for a total of four operations RPG

11 Intra-Hour Results, Wind Ramp Down Single switch operation of -100 Mvar at Tonkawas Single switch operations of -50 Mvar at Nazareth, Edith Clarke, Tesla, Tonkawas North, and Gillespie Single switch operation of -30 Mvar at Oklaunion RPG

12 Conclusion TSPs have the information they need to specify the breakers they are ordering. Coordination of the operations of nearby shunts will be necessary to prevent hunting. ERCOT will coordinate a TSP operator meeting to develop voltage control procedures for the CREZ regions. RPG