QSE Managers Working Group November 7 th 2011 NPRR 334 – Additional Analysis

2 Background NPRR limits the amount of Regulation from a single Resource to be less than or equal to X% of system wide Regulation requirement. When a limited number of Resources are providing Regulation Service, ERCOT is vulnerable to unavailability of the service in Real Time due to –Failure to provide due to Resource failure –Failure to provide due to Resource being moved up to lower ramp rate region –Un-deliverability due to transmission constraint Mostly these type of issues happen during Operating period when SASM cannot be opened to cover the unavailable AS The NPRR increases the distribution of Regulation Service responsibilities and hence reduces reliability risks Reduces the need for committing Resource in RUC for AS and reduces the number of SASMs Reduces the need for manual intervention by operator to enter offset to recover frequency if units providing regulation are not responding to regulation deployment.

3 August 11 PDCWG Comments The PDCWG believes that the initial value of X% should be set at 30%. This is based on the average Primary Frequency Response of the ERCOT System that since Dec 1, 2010 is approximately -490 MW/0.1 Hz. The momentary loss of 30% of Regulation Service from a single Resource would impact ERCOT System frequency approximately +/ Hz which is well within the frequency trigger limit of the BAAL field trial. With SCED’s ability to recover Regulation Service every five minutes, the loss of Regulation Service will be minimized. The 30% limit will require a minimum of four Resources to provide the service.

4 Resources carrying >= 30% Reg requirement This shows information about 5 min intervals in which at least one resource is providing more than 30% regulation requirement # intervals w/Resourc e RegUp >=30% # intervals w/Resourc e RegDn >=30% # intervals in month Percent of SCED Executions At Least One Resource Had 30% or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 30% or More of the Reg. Down # of hrs regup Dec %0.07%119 Jan %0.17%251 Feb %0.17%372 Mar %1.58%179 Apr %6.38%100 May %1.61%104 Jun %11.53%32 Jul %6.03%79 Aug %7.04%71 Sep %0.17%130

5 Resources carrying >= 40% Reg requirement This shows information about intervals in which at least one resource is providing more than 40% regulation requirement # intervals w/Resource RegUp >=40% # intervals w/Resource RegDn >=40% # intervals in month Percent of SCED Executions At Least One Resource Had 40% or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 40% or More of the Reg. Down # of hrs regup Dec %0.00%44 Jan %0.00%33 Feb %0.01%91 Mar %0.05%24 Apr %2.00%3 May % 0 Jun %0.09%0 Jul %0.04%0 Aug %0.04%7 Sep %0.00%12

6 Resources carrying >= 50% Reg requirement This shows information about intervals in which at least one resource is providing more than 50% regulation requirement # intervals w/Resourc e RegUp >=50% # intervals w/Resourc e RegDn >=50% # intervals in month Percent of SCED Executions At Least One Resource Had 50% or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 50% or More of the Reg. Down # of hrs regup Dec %0.00%18 Jan %0.00%1 Feb %0.01%2 Mar %0.05%1 Apr %0.00%2 May % 0 Jun %0.02%0 Jul %0.01%0 Aug % 0 Sep % 0

7 Undeliverable in the operaing hour Percent of 5 minute intervals in a month when transmission constraint was affecting # of resources carrying Reg-Up Month-Year AVG Number of Resources carrying Reg-Up Max Number of Resources carrying Reg- Up Min Number of Resources carrying Reg- Up 0-5 Resources 5-15 Resources Resources Greater than 25 Resources sum Dec (1.20% intervals >35) 13 (0.067%<20) 27.09%12.47%6.35%0.16%46.07% Jan (0.44% intervals >30) 8 (5.11%<20)7.76%12.70%3.99%0.62%25.07% Feb (2.43% intervals >30) 6 (9.62%<10)13.99%15.35%7.97%1.62%38.93% Mar (2.14% intervals > 25) 6 (6.18% < 10)7.27%6.90%7.21%0.02%21.40% Apr (1.67% intervals > 30) 9 (20.60% < 15) 19.15%15.03%6.14%0.23%40.55% May (16.08% intervals > 25) 10 (10.41% < 15) 25.58%20.48%11.74%0.90%58.70% Looking at resources carrying reg that are constrained (LMP< System lambda) 1% ~= ninty 5-minute intervals or 7.5 hrs

8 NPRR 334 – Additional Analysis Evaluated based on amount of MWs on a single resource versus percentage of requirement Evaluated based on number of resources carrying this amount

9 NPRR 334 – Additional Analysis Intervals with a single Resource carrying >= 50 MW # intervals w/Resource RegUp >=50MW # intervals w/Resource RegDn >=50MW # intervals in month Percent of SCED Executions At Least One Resource Had 50MW or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 50MW or More of the Reg. Down Dec %99.03% Jan %98.30% Feb %98.16% Mar %93.77% Apr %98.62% May %90.78% Jun %94.58% Jul %97.14% Aug %93.58% Sep %96.77% Total %96.10%

10 NPRR 334 – Additional Analysis Intervals with a single Resource carrying >= 100 MW # intervals w/Resource RegUp >=100MW # intervals w/Resource RegDn >=100MW # intervals in month Percent of SCED Executions At Least One Resource Had 100MW or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 100MW or More of the Reg. Down Dec %7.66% Jan %1.95% Feb %10.94% Mar %15.68% Apr %14.33% May %7.84% Jun %38.44% Jul %38.79% Aug %22.36% Sep %7.97% Total %16.43%

11 NPRR 334 – Additional Analysis Intervals with a single Resource carrying >= 150 MW # intervals w/Resource RegUp >=150MW # intervals w/Resource RegDn >=150MW # intervals in month Percent of SCED Executions At Least One Resource Had 150MW or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 150MW or More of the Reg. Down Dec %0.00% Jan %0.13% Feb %0.30% Mar %0.19% Apr %0.16% May %0.00% Jun %0.00% Jul %1.60% Aug %0.01% Sep %0.00% Total %0.23%

12 NPRR 334 – Additional Analysis Intervals with a single Resource carrying >= 200 MW # intervals w/Resource RegUp >=200MW # intervals w/Resource RegDn >=200MW # intervals in month Percent of SCED Executions At Least One Resource Had 200MW or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 200MW or More of the Reg. Down Dec %0.00% Jan %0.00% Feb % Mar % Apr % May %0.00% Jun %0.00% Jul % Aug % Sep % Total %0.01%

13 NPRR 334 – Additional Analysis Intervals with a single Resource carrying >= 250 MW # intervals w/Resource RegUp >=250MW # intervals w/Resource RegDn >=250MW # intervals in month Percent of SCED Executions At Least One Resource Had 250MW or More of the Reg. Up Percent of SCED Executions At Least One Resource Had 250MW or More of the Reg. Down Dec %0.00% Jan % Feb % Mar % Apr % May % Jun %0.00% Jul % Aug % Sep % Total %0.01%

14 NPRR 334 – Additional Analysis # of Resources with >=50M W of Regup with >=100M W of Regup with >=150MW of Regup with >=50MW of Regdn with >=100MW of Regdn with >=150MW of Regdn Total Intervals where X Resources carried above X MWs (December – September)