1 Market Trials Real-Time Market / LFC Weekly Update May 21, 2010

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 Agenda Antitrust Admonition Environment Report –Planned / unplanned outages –Known Issues Standing Reports and Updates –General reminders / updates –RTM / LFC Update –LFC Calendar Update –2-Hour LFC Test 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

Market Trials 2010 Roadmap 4

5 Environment Report: Planned / Unplanned Nodal Outages Planned Outages –N/A Unplanned Outages –05/15/2010 2:05 A.M. – 5:05 A.M. Performance degradation with SCED processes were noted during the reported time period. The root cause has been identified to a system backup being executed around same time frame.

6 Known Issues Recently Opened Issues –MIS MIS Notices Tab is Returning an ERROR Message –Steps to reproduce: »1. Log in to MIS using any valid DC »2. Navigate to the Notices tab –Expected Behavior: List of notices should display –Actual Behavior: Error message displays –EWS to MIR Update Weather Data section in EIP External Interfaces Specification to align with CDR Report –In a future update to the EIP External Interfaces Specification, the XML example in Section , Weather Data, will be aligned with the actual CDR Report by removing all weather-data tags except for (the temperature data is the only data that needs to be provided in this report because it is the only data that is used in common by both the load forecasting and dynamic ratings applications).

7 Known Issues Recently Opened Issues (continued) –EWS to MIR Update Dynamic Ratings section in EIP External Interfaces Specification –In a future update to the EIP External Interfaces Specification, the "2-hour" rating type identified in section , Dynamic Ratings, will need to be changed to "Emergency."

8 Known Issues Recently Closed Issues –EWS to MIR EWS responses were failing for Market Info: DynamicRatings and LMPs_RTM when both durations were being set to the maximum –EIP The following reports are now available via EWS: –4.3.8 Forecasted Load –4.3.9 System Load – Market LMPs and SPPs – SCED Violated constraints – Weather Data – Responsive Reserve Capacity – Non-Spinning Reserve – Undeployed Reg-Up and Reg-Down – Available Capacity – Total ERCOT Load – Total ERCOT Gen Op Reserve – System Parameters

9 Standing Reports and Updates: General Reminders / Updates Real-Time Known Issues List –The Updated Real-Time Known Issues List will post overnight to the Readiness Center ( Network Model Update –The current system loaded from the model 05/19/10 –Next scheduled load is 05/24/10 Reminder to continue submitting Wind Forecast Values for COP –QSEs representing Wind Generation Resources (WGRs) are requested to update the COP on an hourly basis with the Resource-Specific forecast value to support HRUC solutions (required by May 31)

3/20/ Real Time Market / LFC Update

11 SCED Week 16 $2250 intervals every day except Friday Non $2250 intervals typically between $20 - $60. Thursday 5:05 am - 5:50 am Garrott - Midtown 138KV (LMP range of $18 - $43) 10:30 am - 11:25 am Garrott - Midtown 138KV (LMP range from $25 - $65) 3:45 pm - 5:00 pm Copperas Cove TU - Killeen Clark Road 138KV & 3:45 pm - 5:40 pm Richland Chambers - Trinidad SES 345KV (LMP range from $27 - $70) Friday 6:55 am - 9:25 am Turnersville/Buda 138kV (LMP -$281 to $484) 9:15 am - 9:25 am Garrott - Midtown 138KV (LMP -$140 - $883) Monday 2:45 pm - 2:55 pm West-to-North Stability (LMP $0.34 to $2591) 3:15 pm - 3:20 pm Garrott - Midtown 138KV (LMP $2073 to $3120)

Missed MIS LMP Reports 12 Database performance trigger to be fixed in next MMS patch 5/15/10 07:50:20 5/16/10 11:45:18 5/17/10 13:10:16 5/17/10 18:10:33 5/18/10 19:25:15

13 LFC Calendar Update

14 LFC Calendar Update LFC Calendar (MT4) 76 QSEs/Sub-QSEs were targeted for Individual QSE tests 73 scheduled a test window (99.15% of Generation) 3 were unable to test due to modeling issues 70 QSEs/Sub-QSEs completed all testing or an attestation (96.86% of Generation) 6 QSE/Sub-QSEs (2.78% of Generation) are working with ERCOT to resolve remaining issues, including: Modeling issues ICCP issues Additional testing needed The updated LFC Calendar will deploy overnight to the Readiness Center at Submit questions regarding the LFC Calendar to

15 LFC Calendar Update LFC Calendar (MT5) – Upcoming Key Dates Week of May 24 –Publish the 8-Hour LFC operational test scenarios to the Readiness Center Week of June 1 –ERCOT and Market Participants begin 24x7 telemetry support –Conduct 8-Hour LFC Workshop Discuss operational test scenarios that will be conducted during the 8- Hour LFC Test June 1 – 11 –Prepare for the 8-Hour LFC Test June 4 –Report results from the 2-Hour LFC Test on the Real-Time Market Call Week of June 14 –Conduct the 8-Hour LFC Test (June 16 – 18 timeframe) –Publish the 48-Hour LFC operational test scenarios to the Readiness Center

Hour LFC Test Update

Hour LFC Test Update Test ActivitiesApprox Timeline Market WebEx start8:00 AM ERCOT - MP pre-test troubleshooting period8:00 AM - 11:15 AM Test start11:15 AM Zonal-Nodal cutover11:15 AM - 11:55 AM System frequency controlled by nodal systems11:55 AM - 12:25 PM Nodal-Zonal cutover12:25 PM - 1:00 PM Test end1:00 PM Market WebEx end1:15 PM

Hour LFC Test Update 2-Hour LFC Test Update (continued) Constraints (activated in both Nodal and Zonal)Start Time Garrott - Midtown OC3Loss of Greens Bayou - Gable and Hardy - Crocket 138KV overloads Midtown - Garrott 138KV - 102% of 317 MVA rating. 10:45 AM Bellaire Autotransformer OC3Loss of Bellaire 345/138KV autotransformer 2 overloads Bellaire 345/138KV autotransformer % of 600 MVA rating. 11:45 AM

Hour LFC Test Update 2-Hour LFC Test Update (continued) Common ICCP Issues Identified/Solved During the Test  On/Off status incorrect for LBST/RBST points  Resource Status Codes (RSTs) coming in as SUSPECT  OFF RST being sent for units that were online and generating MW  RST of ON instead of ONREG being sent for units with REG Responsibilities  RST of ONREG being sent for units in hours where they had no REG Responsibility  Non-zero LSLs being sent for WGRs  HSLs for WGRS being set to capacity rather than un-curtailed MW output  MPs updating REG Responsibilities slowly  RegUp & RegDown Responsibilities switched for one another  AS Responsibilities not lining up between Nodal and Zonal (i.e., wrong AS Type or wrong MW value)

20 State Estimator Convergence

21 State Estimator Convergence Update State Estimator Daily Convergence Statistics (these percentages are graphed in the next slide) MonthDay% Convergence (Including Solved w/ Mismatch) MAY MAY MAY MAY MAY MAY15100 MAY MAY MAY MAY

22 State Estimator Convergence Update

23 Q&A Q&A / Open Forum

24 Appendix

25 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:

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

27 Market Trials Handbooks –Available on the Readiness Center at the following links Real Time Market / LFC covering Phase Outage Scheduler covering Phase CRR covering release Phase Settlements / COMs covering Phase Day Ahead Market