April 16, 2010 RPG Meeting ERCOT Five-Year Transmission Plan Update Jeff Billo

2 April 16, 2010RPG Meeting YTP 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

3 April 16, 2010RPG Meeting YTP 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

4 April 16, 2010RPG Meeting YTP 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 ~ minutes for full AC SCOPF **********Not an endorsement for Powerworld***********

5 April 16, 2010RPG Meeting YTP 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***********

6 April 16, 2010RPG Meeting YTP 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 ~99 th percentile load ~95-100% peak load Assumed low/ zero curtailment at low wind generation output

7 April 16, 2010RPG Meeting YTP 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 1 st quantile represents similar statistical probability to one standard deviation below mean for a normal distribution (17%) 1 st Quantile 16.67%83.33%

8 April 16, 2010RPG Meeting YTP 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 Region High Output % Low Output % 1 st (of 6) Quantile % Proposed Output % McCamey Central West West Abilene Lower Panhandle Coast Culberson

9 April 16, 2010RPG Meeting YTP Reliability Analysis Next Steps –Wrap-up 2015 reliability analysis –Perform project back-out to validate results –Send initial project set out for comment –Begin reliability analysis

10 April 16, 2010RPG Meeting March 12, 2010 Questions?