ERCOT Five-Year Transmission Plan Update

1. ERCOT Five-Year Transmission Plan Update Jeff Billo RPG Meeting

2. 2009 5YTP Status • Report • Final report posted! • AC analysis • 2010 AC Case addendum report sent to TOs for comment • No voltage criteria violations • Some thermal exceedances • 2013 AC Case work ongoing RPG Meeting

3. 2010 5YTP Reliability Analysis • 2015 Reliability Analysis • Initial n-1 reliability analysis complete • Initial generation outage analysis complete except for North/ North Central • Due to high load in North Central weather zone there is little reserve margin when large generation units are taken out of service in the region • Low wind scenarios under study RPG Meeting

4. 2010 5YTP Reliability Analysis Tools • Powerworld SCOPF • Security Constrained Optimal Power Flow • Utilizes cost curve for each unit • Optimizes cost • Assigns penalty cost for every MVA overload • Can set to optimize for minimal change in dispatch • Performs AC contingency analysis then dispatches around problems • Must perform iteratively • Can have “see-saw” constraints • Reports “unenforceable constraints” for reliability problems that cannot be fixed with redispatch • Run times ~ 40-60 minutes for full AC SCOPF • **********Not an endorsement for Powerworld*********** RPG Meeting

5. 2010 5YTP Reliability Analysis Tools • TARA SCRD • Transmission Adequacy and Reliability Assessment • Security Constrained Reliability Dispatch • Set to optimize for minimal change in dispatch • Assigns penalty factor for every MVA overload • Can also run SCOPF • Performs simultaneous DC contingency analysis and redispatch • Runs final AC powerflow check at end of run • May have slight overload in AC at end of run • Reports overloads in Excel spreadsheet for reliability problems that cannot be fixed with redispatch • Run times ~ 1 minute for SCRD • N-1-1 analysis • Runs contingency subset for first n-1 with full contingency set for second -1 • Performs SCRD (or SCOPF) for each of first contingency set run • Used to run generation outage analysis in 5YTP • Run times ~ 2-3 hours for ERCOT generation outage and full SCRD • **********Not an endorsement for TARA*********** RPG Meeting

6. 2010 5YTP Low Wind Scenario Analysis • Low wind scenario(s) studied for reliability analysis • Purpose is to find local reliability problems if wind is not blowing at or near peak load • Scenario selection • Divided ERCOT into six wind generation regions • Similar to work done for SSWG wind dispatch analysis • McCamey, Central West, West Abilene, Lower Panhandle, Coast, Culberson County • Analyzed historical (2009) wind output in each region for ERCOT load above 60,000 MW • 76 hours in 2009 • ~99th percentile load • ~95-100% peak load • Assumed low/ zero curtailment • at low wind generation output RPG Meeting

7. 2010 5YTP Low Wind Scenario Analysis • Low wind scenario(s) data observations • Regional wind output has some correlation to system load (correlation factor not calculated) • Regional wind output data above 60 GW load does not fit a normal distribution • Data set for each region divided into six quantiles • 16.67% of data points will be lower than first quantile • 83.33% of data points will be higher than first quantile • 1st quantile represents similar statistical probability to one standard deviation below mean for a normal distribution (17%) 1st Quantile 16.67% 83.33% RPG Meeting

8. 2010 5YTP Low Wind Scenario • Results of data analysis • Will create six low wind cases for reliability analysis • Each of six regions will have wind generation in respective region set to above output % • All other wind generation in case will be left at SSWG output levels RPG Meeting

9. 2010 5YTP Reliability Analysis • Next Steps • Wrap-up 2015 reliability analysis • Perform project back-out to validate results • Send initial project set out for comment • Begin 2011-2014 reliability analysis RPG Meeting

10. Questions? March 12, 2010 RPG Meeting