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

2. 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. 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 +/-0.0613 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. 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 Dec142571059313.45%0.07%119 Jan300616922032.60%0.17%251 Feb445914828253.84%0.17%372 Mar2147145915923.44%1.58%179 Apr1195569891713.40%6.38%100 May1250147913113.69%1.61%104 Jun384102488794.32%11.53%32 Jul949544902310.52%6.03%79 Aug85663389929.52%7.04%71 Sep156015880517.72%0.17%130

5. 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 Dec5310105935.01%0.00%44 Jan393092204.26%0.00%33 Feb10951828213.22%0.01%91 Mar284591593.10%0.05%24 Apr3517889170.39%2.00%3 May0091310.00% 0 Jun0888790.00%0.09%0 Jul0490230.00%0.04%0 Aug85489920.95%0.04%7 Sep141088051.60%0.00%12

6. 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 Dec2120105932.00%0.00%18 Jan12092200.13%0.00%1 Feb29182820.35%0.01%2 Mar6591590.07%0.05%1 Apr20089170.22%0.00%2 May0091310.00% 0 Jun0288790.00%0.02%0 Jul0190230.00%0.01%0 Aug1189920.01% 0 Sep0088050.00% 0

7. 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 15-25 Resources Greater than 25 Resources sum Dec-1031 44 (1.20% intervals >35) 13 (0.067%<20) 27.09%12.47%6.35%0.16%46.07% Jan-1114 39(0.44% intervals >30) 8 (5.11%<20)7.76%12.70%3.99%0.62%25.07% Feb-1117 41 (2.43% intervals >30) 6 (9.62%<10)13.99%15.35%7.97%1.62%38.93% Mar-1117 29 (2.14% intervals > 25) 6 (6.18% < 10)7.27%6.90%7.21%0.02%21.40% Apr-1119 41 (1.67% intervals > 30) 9 (20.60% < 15) 19.15%15.03%6.14%0.23%40.55% May-112139 (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. 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. 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 10518104901059399.29%99.03% Jan 922090639220100.00%98.30% Feb 828281308282100.00%98.16% Mar 915985889159100.00%93.77% Apr 88948794891799.74%98.62% May 913182899131100.00%90.78% Jun 887983988879100.00%94.58% Jul 89648765902399.35%97.14% Aug 899284158992100.00%93.58% Sep 880585218805100.00%96.77% Total 90844874539100199.83%96.10%

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 29638111059327.97%7.66% Jan 8482180922092.00%1.95% Feb 7988906828296.45%10.94% Mar 91311436915999.69%15.68% Apr 82781278891792.83%14.33% May 8990716913198.46%7.84% Jun 79663413887989.72%38.44% Jul 74563500902382.63%38.79% Aug 63002011899270.06%22.36% Sep 6634702880575.34%7.97% Total 74188149539100181.52%16.43%

11. 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 8140105937.68%0.00% Jan 122012922013.23%0.13% Feb 257625828231.10%0.30% Mar 270917915929.58%0.19% Apr 210114891723.56%0.16% May 44990913149.27%0.00% Jun 367088794.13%0.00% Jul 9714490231.08%1.60% Aug 267189922.97%0.01% Sep 147088051.67%0.00% Total 147972139100116.26%0.23%

12. 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 1470105931.39%0.00% Jan 49092200.53%0.00% Feb 1182820.01% Mar 5591590.05% Apr 0089170.00% May 5091310.05%0.00% Jun 13088790.15%0.00% Jul 0090230.00% Aug 1189920.01% Sep 0088050.00% Total 2217910010.24%0.01%

13. 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 1210105931.14%0.00% Jan 0092200.00% Feb 1182820.01% Mar 5591590.05% Apr 0089170.00% May 0091310.00% Jun 13088790.15%0.00% Jul 0090230.00% Aug 1189920.01% Sep 0088050.00% Total 1417910010.15%0.01%

14. 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 1 498648442140421577414526212 2 1563419312719217914191 3 20147595036224227 4 23718484 162861 5 14984 7765 6 6953 2506 7 2698 671 8 1192 192 9 456 28 10 67 18 11 9 Total 9084474188147978745314953213 Intervals where X Resources carried above X MWs (December – September)