1. http://nodal.ercot.com 1 Market Trials Real-Time Market / LFC Weekly Update April 30, 2010

2. http://nodal.ercot.com 2 Antitrust Admonition ANTITRUST ADMONITION ERCOT strictly prohibits Market Participants and their employees who are participating in ERCOT activities from using their participation in ERCOT activities as a forum for engaging in practices or communications that violate the antitrust laws. The ERCOT Board has approved guidelines for members of ERCOT Committees, Subcommittees and Working Groups to be reviewed and followed by each Market Participant attending ERCOT meetings. If you have not received a copy of these Guidelines, copies are available at the Client Relations desk. Please remember your ongoing obligation to comply with all applicable laws, including the antitrust laws. DISCLAIMER All presentations and materials submitted by Market Participants or any other Entity to ERCOT staff for this meeting are received and posted with the acknowledgement that the information will be considered public in accordance with the ERCOT Websites Content Management Operating Procedure.

3. http://nodal.ercot.com 3 Agenda Antitrust Admonition Environment Report –Planned / unplanned outages –Known Issues Standing Reports and Updates –General reminders / updates –RTM / LFC Update –LFC Update –State Estimator Convergence Statistics Question and Answers / General Discussion ERCOT asks that Market Participants log into the WebEx session using their company name and then their name. This will allow ERCOT to take roll-call offline

4. Market Trials 2010 Roadmap http://nodal.ercot.com 4

5. http://nodal.ercot.com 5 Environment Report: Planned / Unplanned Nodal Outages Planned Outages –Planned Outages - N/A Unplanned Outages 04/27/10 6:00 – 7:00 P.M. –Market Manager application availability may have been briefly interrupted as a result of a site fail over test conducted during this time period 04/28/10 6:00 – 7:00 P.M. –Market Manager application availability may have been briefly interrupted as a result of a site fail over test conducted during this time period 04/29/10 1:30 – 2:30 P.M. –AS Awards for operating day 04/30/10 were unavailable for download via EWS and Market Manager applications. Issue was identified to a report posting error and was corrected at 2:30 P.M. 04/29/10 5:00 – 5:30 P.M. –EWS system was patched up to address defect associated with RUC Startup/Shutdown instruction set report. Interruption with Bid Submission & Query services may have been noticed during this period.

6. http://nodal.ercot.com 6 Environment Report: Known Issues New Real-Time Known Issues –Current Day Reports NP3-217-Forecasted Temperature Adjusted Dynamic Ratings –In this MT3 report, there are duplicate and missing delivery hour records being published in the report output. –A bug in CDR code was found to be causing this error. The issue has been corrected in development. Issue this week that is already resolved: –Software migration over the weekend set the energy offer floor to $-50 instead of $-250. Because of this, some offers were canceled during Phase 2 validation. The issue was resolved Monday afternoon.

7. http://nodal.ercot.com 7 Standing Reports and Updates: General Reminders / Updates Real-Time Known Issues List –The Updated Real-Time Known Issues List posted April 28 to the Readiness Center (http://nodal.ercot.com/readiness/markettrials/rtm/index.html).http://nodal.ercot.com/readiness/markettrials/rtm/index.html Network Model Update –The current system loaded from the model 4/14/10 –Next scheduled load is 5/3/10 Nodal Market Readiness Seminar #4 is scheduled for May 25, 2010 –See meeting details in April 21 Market Notice or online at http://www.ercot.com/calendar/2010/05/20100525-MT http://www.ercot.com/calendar/2010/05/20100525-MT

8. http://nodal.ercot.com 8 Standing Reports and Updates: General Reminders / Updates Unit Parameters needed for Frequency Control –ERCOT will begin working with Market Participants to collect four unit parameters that affect ERCOT’s deployments and protocol reporting: Unit Offline Limit (%), Unit Online Deadband (%) Frequency Deviation Deadband (HZ) Frequency Bias –This topic will be scheduled for discussion at the May 4 NATF meeting (http://www.ercot.com/calendar/2010/05/20100504-NATF)http://www.ercot.com/calendar/2010/05/20100504-NATF Wind Forecast Values for COP –Short-Term Power Forecast (STWPF) / Wind Generation Resource Production Potential (WGRPP) Beginning May 1, QSEs representing Wind Generation Resources (WGRs) will need to update the COP on an hourly basis with the Resource-Specific STWPF/WGRPP value to support HRUC solutions (required by May 31)

9. http://nodal.ercot.com 9 Standing Reports and Updates: General Reminders / Updates Delay in Real-Time Reports for MT Phase 5: –The following RT Reports scheduled for MT Phase 5 will be released late: EMIL IDReportStatus NP8-383Monthly Non-Spin Performance Report Released to iTest 4/19 NP8-501-ER Monthly Resource Energy Deployment Performance Report Released to iTest 4/19 NP8-541-ERMonthly Responsive Reserve Performance Report Released to iTest 4/19 NP6-552-CDGroup 1 and Group 2 Load Resources for RRSTo Be Release to iTest 05/06

10. http://nodal.ercot.com 10 Standing Reports and Updates: General Reminders / Updates Changes to Market Call Schedule: –Beginning May 7, the times the market call schedule will change as follows: 09:00 AM - 09:30 AM Outage Scheduling 09:30 AM - 10:00 AM Congestion Revenue Rights 10:00 AM - 11:00 AM Day Ahead Market / RUC / SASM 11:00 AM - 12:00 PM Real Time Market / LFC 12:00 PM - 01:00 PM Break 01:00 PM - 02:00 PMCOMS/Settlements –WebEx Details will be posted at: http://www.ercot.com/committees/nodal/mt/ http://www.ercot.com/committees/nodal/mt/

11. 3/13/2016 http://nodal.ercot.com 11 Real Time Market / LFC Update

12. http://nodal.ercot.com 12 SCED Week 13 Friday 11:45 – 6:25 pm at $2250 W-N constraint binding Thu for 91 intervals (7h 35m) throughout the day and Wed from 6:50 am – 9:00 am. Wed Putnam to Leon on loss of Graham 345 kV 11:25 am to 4:35 pm (intermittent)

13. Missed MIS LMP Reports http://nodal.ercot.com 13 MMS Upgrade on 4/24 causing timing issue – SCED trigger completion trigger sent too soon to report generator, resulting in error; emergency fix deployed on Friday, 4/30 MMS upgrade addresses previous issue involving missed trigger generation

14. http://nodal.ercot.com 14 LFC Update: Status of Individual QSE Tests for LFC LFC Calendar Status 76 QSEs/Sub-QSEs are currently targeted for Individual QSE tests 73 have scheduled a test window (99.15% of Generation) 3 are currently unable to test due to modeling issues 57 QSEs/Sub-QSEs have completed all testing or an attestation (91.85% of Generation): The updated LFC Calendar will deploy overnight to the Readiness Center at http://nodal.ercot.com/readiness/markettrials/rtm/index.html http://nodal.ercot.com/readiness/markettrials/rtm/index.html Submit questions regarding the LFC Calendar to markettrials@ercot.commarkettrials@ercot.com ANPCPSFORMOSAMP2 ENERGYPSEG_SQ2 GPLCPSSQ1FPL_KEIRNEXTERARIONGL GPL_SQ2DIRECTINVENER_CMPSQ1NEXTERA_SQ1SHERBINO AENDIRECTSQ2INVENER_CMPSQ2NEXTERA_SQ2SILVER_STAR AENSQ1DUKEINVENERGYSQ4NEXTERA_SQ3STEC AEPCEAGLEJ_ARONSQ1NEXTERA_SQ4STEC_SQ2 AEPSQ3EAGLE_SQ4LCRANRG_SQ1TENASKA BPTXSQ1EC_AND_R_SQ1LUMINANTNRG_TEXASTRQ1_SQ1 BRAZOSEC_AND_R_SQ2LUMINANTSQ1OPTIM_ENERGYTRQ4_SQ4 BTUQSEEC_AND_R_SQ4LUMINANTSQ2OPTIMENERGYSQ1 CALPINEEC_AND_R_SQ5MORGAN_SQ3OXY CONSTELLATIONEC_AND_R_SQ6MORGAN_SQ4PSEG_SQ1

15. http://nodal.ercot.com 15 LFC Update: Status of Individual QSE Tests for LFC Upcoming LFC QSE Tests Upcoming QSE LFC Tests through April 30: 5/4/2010GDF SUEZ 5/5/2010EDISON MISSION Available Test windows The following test windows are available through May 7: DateMorningAfternoon 5/4/20109am-12pmunavailable 5/5/2010unavailable1pm-4pm 5/6/20109am-12pm1pm-4pm 5/7/20109am-12pm1pm-4pm

16. http://nodal.ercot.com 16 LFC Update: Upcoming Key Dates Upcoming Key Dates for LFC May 3 - May 7: Final testing period for individual QSE LFC tests May 6: 2-Hour LFC Test Workshop (Market Notice sent 4/28) –WebEx Workshop, 10 AM – 12 PM –Meeting materials will be posted at http://www.ercot.com/calendar/2010/05/20100506-MT http://www.ercot.com/calendar/2010/05/20100506-MT Week of May 17 – Conduct 2-Hr Test –Currently targeting May 19, 20, or 21 –A Market Notice confirming the test date will be sent two days prior –A Market Notice confirming the test start/end times will be sent the day of the test

17. http://nodal.ercot.com 17 LFC Update: Artifacts for the 2-Hour LFC Test Artifacts for the 2-Hour LFC Test The 2-Hour LFC Test Approach document and related artifacts are posted on the Readiness Center at http://nodal.ercot.com/readiness/mar kettrials/rtm/index.html http://nodal.ercot.com/readiness/mar kettrials/rtm/index.html Artifacts include: –2-Hour LFC Test Approach –Control Room Procedure for the Full System LFC Test –White Paper - Settlement of Phase 3 LFC Testing

18. http://nodal.ercot.com 18 State Estimator Convergence Update State Estimator Daily Convergence Statistics (these percentages are graphed in the next slide) MonthDay% Convergence (Including Solved w/ Mismatch) APR1999.30 APR2099.66 APR2198.65 APR2299.27 APR23100 APR2498.92 APR25100 APR2697.89 APR2798.97 APR2897.05

19. http://nodal.ercot.com 19 State Estimator Convergence Update

20. http://nodal.ercot.com 20 Q&A Q&A / Open Forum

21. http://nodal.ercot.com 21 Appendix

22. http://nodal.ercot.com 22 URLS and EMAIL ADDRESS FOR SUPPORT URLs for access the Nodal Production systems –MIS: https://mis.ercot.com/pps/tibco/mis/https://mis.ercot.com/pps/tibco/mis/ –Market Manager: https://mis.ercot.com/pps/tibco/mis/ Click the ‘Applications’ tab in the upper menu. Link is in the ERCOT Applications portlethttps://mis.ercot.com/pps/tibco/mis/ –CRR: https://mis.ercot.com/pps/tibco/mis/ Click the ‘Markets’ Link in the upper menu. Click CRR in the Market sub menuhttps://mis.ercot.com/pps/tibco/mis/ –EWS: https://misapi.ercot.com/2007-08/Nodal/eEDS/EWShttps://misapi.ercot.com/2007-08/Nodal/eEDS/EWS Reminder: Market Trials email address change: ERCOT asks that MPs use the markettrials@ercot.com email address for questions from this point forwardmarkettrials@ercot.com –This will begin the phasing out of eds2@ercot.com, eds3@ercot.com and eds4@ercot.com email addresses.eds2@ercot.comeds3@ercot.com eds4@ercot.com –A centralized address will no longer require MPs to “guess” which email address to use for their questions –We have implemented a more effective method of routing and responding to emails using this address –The old eds emails can continue to be used until 2009 hold over efforts are completed (such as telemetry outreach)

23. http://nodal.ercot.com 23 Market Trials Handbooks –Available on the Readiness Center at the following links Real Time Market / LFC covering Phase http://nodal.ercot.com/readiness/markettrials/rtm/index.htmlhttp://nodal.ercot.com/readiness/markettrials/rtm/index.html Outage Scheduler covering Phase http://nodal.ercot.com/readiness/markettrials/os/index.htmlhttp://nodal.ercot.com/readiness/markettrials/os/index.html CRR covering release Phase http://nodal.ercot.com/readiness/markettrials/crr/index.htmlhttp://nodal.ercot.com/readiness/markettrials/crr/index.html Settlements / COMs covering Phase http://nodal.ercot.com/readiness/markettrials/coms/index.htmlhttp://nodal.ercot.com/readiness/markettrials/coms/index.html Day Ahead Market http://nodal.ercot.com/readiness/markettrials/dam/index.htmlhttp://nodal.ercot.com/readiness/markettrials/dam/index.html