ercot five-year transmission plan update

April 16, 2010

RPG Meeting

ERCOT Five-Year Transmission Plan Update

Jeff Billo

April 16, 2010 2 RPG Meeting

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


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


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***********


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***********


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


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%


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

RegionHigh

Output %Low

Output %1st (of 6)

Quantile %Proposed Output %

McCamey 46.5 0.5 6.1 6.0

Central West

29.2 0.4 2.0 2.0

West Abilene

36.1 0.0 3.0 3.0

Lower Panhandle

64.0 0.5 8.0 8.0

Coast 90.6 19.8 41.8 40.0

Culberson 22.4 -0.7 -0.3 0.0


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

April 16, 2010 10 RPG Meeting March 12, 2010

Questions?

ercot five-year transmission plan update

Documents