1. http://nodal.ercot.com 1 Market Trials Real-Time Market / LFC Weekly Update April 16, 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: Status of Individual QSE Tests for LFC –Telemetry Outreach 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 04/23/10 – 04/25/10 –ERCOT will be performing the initial release for Phase 5 on 4/23 –Due to the size and complexity of the release, it will be necessary to take systems down periodically throughout the weekend –ERCOT will be running a series of test that Sunday which may result in notifications and / or data in the Nodal Production systems that are associated with that test. 04/16/10 06:00 P.M. – 04/16/2010 07:00 P.M & 04/17/10 10:00 A.M. – 04/17/2010 11:00 A.M. –Market Manager site failover testing is planned during this period. A brief delay in processing may occur. If authentication errors are encountered, signing back into the application will resolve the issue. Unplanned Outages 04/13/10 12:00 P.M. – 04/13/2010 02:30 P.M. –Authentication exceptions were being reported against EWS submissions. Issue occurred as a result of an update to the identity management system. Market Manager was fully functional during this time period. 04/12/10 09:00 A.M – 6:00 P.M –MPIM Application performance issues were noted during the day. MPs were unable to assign certain roles to user certificates. Any new certificates created during this period with “NMMS” or “EMMS” roles will need to be completely terminated and reissued.

6. http://nodal.ercot.com 6 Environment Report: Known Issues New Real-Time Known Issues –EWS to MIR MW values in CDR reports contain multiple decimal points, although they should be represented by a single decimal point The MW values in CDR need to contain a single decimal point to prevent rounding errors in reports pulled through External Web Services (EWS) so that reports pulled via MIS and EWS are consistent. –MMS MM The MMS UI does not highlight the correct error area on client-side validation for Create/Update TPO –Highlighting Error #1: »If any value except EOC Price is left empty on a TPO submission, then upon submitting/updating that TPO the UI states to correct the entries highlighted in orange--but only ""Hot Start-Up"" is highlighted. This highlighting is only correct when the Hot Start-Up is left empty. –Highlighting Error #2: »If EOC Price is left empty, nothing happens after pressing the update button. The EOC price should be highlighted and the ""correct the entries"" message should be displayed."

7. http://nodal.ercot.com 7 Environment Report: Known Issues Closed Real-Time Known Issues –MMS Validation Rules Incremental Offer submissions are incorrectly rejected whenever a previously submitted Decremental offer Curve started at 0 MW –When an Incremental offer is submitted for the same Resource that a Decremental offer was accepted in which the first MW value is 0, the offer is rejected with an error message stating that the DEC price must be lower than the INC price. The price for the DEC is lower than the INC price, so the submission should not be rejected. Error with the two-hour notification the SCED_TWOHR_FAIL notification –The notification which checks for missing Energy Offer Curves (EOCs) and Output Schedules (OS) for online Resources contains an error such that when a COP is submitted by a different user than the one that entered the EOC/OS, a message is incorrectly issued two hours prior to the start of the Operating Hour stating that the EOC/OS is missing. As a result, QSEs may receive this notification in error for hours in which an EOC/OS actually does exist.

8. http://nodal.ercot.com 8 Standing Reports and Updates: General Reminders / Updates Real-Time Known Issues List –The Updated Real-Time Known Issues List will deploy this evening 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 loads is 5/3/10 Short-Term Power Forecast (STWPF) / Wind Generation Resource Production Potential (WGRPP) POE value –Beginning May 1, QSEs representing Wind Generation Resources (WGRs) will need to update the COP HSL on an hourly basis with the Resource-Specific STWPF/WGRPP value to support HRUC solutions (required by May 31) NP6-904-CD (Systems Parameters Report) will no longer be made available as a report as originally planned. –It will remain available as a web service and as a dashboard

9. 11/24/2015 http://nodal.ercot.com 9 Real Time Market / LFC Update

10. http://nodal.ercot.com 10 SCED Week 11 PI recorder outage Sat – Mon as a result of failover testing activities Monday LMP similar to last Monday; contributed to reaching the $2250 cap (19 intervals, some during PI outage) On 4/13 20:50 LMP lasted ten minutes, followed by one-second LMP Houston area OC3 constraint 4/13 11:50-12:05 ($35 - $44) Note: The West to North Stability limit is now modeled in nodal. Activation has not occurred due to system conditions and wind pattern

11. Missed MIS LMP Reports http://nodal.ercot.com 11 All missed postings have been posted Outage over weekend (4/10 – 4/11) for two reasons: Report trigger not publishing when multiple events running (reported last week) Failover test activities 4/13 missed intervals due to DB deployment activity

12. http://nodal.ercot.com 12 LFC Update: Status of Individual QSE Tests for LFC LFC Calendar Status 76 QSEs/Sub-QSEs are currently targeted for Individual QSE tests 65 have scheduled a test window (94% of Generation) 36 QSE/Sub-QSEs have completed testing (80.28% of Generation): The LFC Calendar was updated on April 15 and posted on the Readiness Center at http://nodal.ercot.com/readiness/markettrials/rtm/index.html http://nodal.ercot.com/readiness/markettrials/rtm/index.html AEPCEAGLEMORGAN_SQ4OPTIM_ENERGY AEPSQ3EAGLE_SQ4MP2 ENERGY OPTIMENERGYS Q1 BRAZOSEC_AND_R_SQ6NEXTERAOXY BTUQSEFORMOSANEXTERA_SQ1RIONGL CALPINEFPL_KEIRNEXTERA_SQ2STEC CPSLCRANEXTERA_SQ3STEC_SQ2 CPSSQ1LUMINANTNEXTERA_SQ4TENASKA DIRECTLUMINANTSQ2NRG_SQ1TRQ1_SQ1 DIRECTSQ2MORGAN_SQ3NRG_TEXASTRQ4_SQ4

13. http://nodal.ercot.com 13 LFC Update: Status of Individual QSE Tests for LFC Upcoming LFC QSE Tests Upcoming QSE LFC Tests through April 16: 4/19/2010JARON (SQ1) 4/20/2010EXELON 4/22/2010GDF SUEZ 4/23/2010BP (SQ1) Submit questions regarding the LFC Calendar to markettrials@ercot.commarkettrials@ercot.com Available Test windows through April 30 DateMorningAfternoon 4/20/2010unavailable1pm-4pm 4/21/20109am-12pm1pm-4pm 4/22/20109am-12pmunavailable 4/23/20109am-12pmunavailable 4/26/20109am-12pm1pm-4pm 4/27/2010unavailable1pm-4pm 4/28/2010unavailable 4/29/20109am-12pmunavailable 4/30/20109am-12pm1pm-4pm

14. http://nodal.ercot.com 14 LFC Update: Upcoming Key Dates Upcoming Key Dates for LFC April 16 – Formal testing period closes for individual QSE LFC tests April 19 – May 7 – Re-testing period for individual QSE LFC tests has been extended through May 7 Week of April 19 – The 2-Hour LFC Test Approach document and related artifacts become available for review Week of May 3 – ERCOT will host a workshop to discuss the upcoming 2-Hour LFC Test Week of May 17 – Conduct 2-Hr Test

15. http://nodal.ercot.com 15 State Estimator Convergence Update State Estimator Daily Convergence Statistics (these percentages are graphed in the next slide) MonthDay% Convergence (Including Solved w/ Mismatch) APR594.54 APR695.07 APR780.75 APR873.45 APR977.32 APR1091.67 APR1193.40 APR1297.71 APR1397.27 APR1499.32

16. http://nodal.ercot.com 16 State Estimator Convergence Update

17. http://nodal.ercot.com 17 Q&A Q&A / Open Forum

18. http://nodal.ercot.com 18 Appendix

19. http://nodal.ercot.com 19 Market Call Schedule Reminder of market call schedule: 09:00 AM-10:00 AM Outage Scheduling 10:00 AM-11:00 AM Congestion Revenue Rights 11:00 AM-12:00 PM Day Ahead Market / RUC / SASM 12:00 PM-01:00 PM Break 01:00 PM-02:00 PM Real Time Market / LFC –WebEx Details will be posted at: http://www.ercot.com/committees/nodal/mt/ http://www.ercot.com/committees/nodal/mt/

20. http://nodal.ercot.com 20 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)

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