1. http://nodal.ercot.com 1 Market Trials Outage Scheduling Weekly Update July 23, 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 Anti-trust Admonition Environment Report –Planned / unplanned outages –CIM Load –Known Issues Standing Reports and Updates –General reminders / updates Outage Scheduler Transition to Go-Live 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 Day-to-day operations summary: Planned / Unplanned Outages of EDS Planned Outages 07/22/2010 8:00 A.M. – 07/26/2010 8:00 A.M. –Migration activities are currently underway in the Nodal production environment and will intermittently affect availability of the following application services: »OS UI »EWS ( Web Services) »MIS –Note: External interface specification 1.19N will take into effect upon completion of these planned activities 07/29/2010 10:00 A.M. – 07/29/2010 10:30 A.M. –Site failover activities are planned for Nodal Market/OS and EMS applications. The outage duration is expected to last no more than 30 minutes from the start of the test. Unplanned Outages N/A

6. http://nodal.ercot.com 6 General reminders / updates New Course: Network Modeling – Outage Scheduling –The objective of this course is to review using outages for network model changes –This course outline will be posted this afternoon with this presentation at: http://www.ercot.com/calendar/2010/07/20100723-MT http://www.ercot.com/calendar/2010/07/20100723-MT –Currently, the dates are being worked on and will be communicated via Market Notice and in the Outage Scheduler Market call 5-Hour LFC test: completed on Wednesday TimeActivity 0800 Hotline call was made by the ERCOT Operator announcing the 1100 start time for the test 0929ERCOT Operators activated an OC3 for solving congestion in Zonal 1100 Hotline call what made announcing the test was starting and the VDI was issued 1119First participating QSE confirms switch over to Nodal control 1214Final participating QSE confirms switch over to Nodal control 1218 Hotline call what made announcing that all participating QSEs on Nodal control 1531 Hotline call what made announcing that participating QSEs were being switched back to Zonal 1535First participating QSE confirms switch back to Zonal control 1616Final participating QSE confirms switch back to Zonal control

7. http://nodal.ercot.com 7 General reminders / updates Market Readiness Seminar #5 –Focus will be on the remaining activities of Market Trials in August and September –Although changes to the 168-Hour test have been discussed at NATF and the Board recently, ERCOT will be detailing August as well as discussing September’s activities to be discussed in upcoming Market forums –Additionally, this seminar will also cover detailed information about Nodal Cutover –Details about MRS #5 and how to attend are located at: http://www.ercot.com/calendar/2010/07/20100728-MT http://www.ercot.com/calendar/2010/07/20100728-MT

8. http://nodal.ercot.com 8 Environment Report: Known Issues Known issues posted to the readiness center at: http://nodal.ercot.com/readiness/markettrials/os/index.html http://nodal.ercot.com/readiness/markettrials/os/index.html Deferred Issues: StatusIssueDescriptionWork Around/Comments Defered Market - Line names have an extra Character "1" appended to the end of the line names. The CIM XML has a class for line name and a sub class for a segment name. To get the Line Segment name the Line Name has to have the Segment Name appended to the end. If a MP doesn't use the Line Segment Name in there system, a "1" was added to the end of the Line Name to represent the Segment. This is confusing to some MP operators and systems. Example:Line NEWTGF04 would be NEWTGF041 with the Segment Name added to the end. The affected Market Participants are working with ERCOT to change the "1" to an "_".

9. http://nodal.ercot.com 9 Environment Report: Known Issues Newly Closed Issues: StatusIssueDescription ClosedNaming convention for lines and line segments If a line doesn't have a line segment name a 1 is added to the end of the line name. ClosedTOO Duration issue When submitting a Transmission Opportunity Outage the outage duration can't exceed the opportunity window. Invalid You can't work with a new TOO when is had an existing TOO that was canceled if any part of the 90 days overlaps. If the user submits a TOO. An outage is submmitted on the Designated Resource from the TOO. The TOO is then canceled by the user. The user submits another TOO on the same piece of equipment. The New TOO will not be able to be approved by ERCOT until the Opportunity Window from the first TOO has passed. Closed You can copy a TOO with dates from any state with dates (reject etc), and it will submit it directly to TOO Rate with dates without a match DR. If the user copies a TOO that has Planned Start and End Dates the system also copies the dates. When the TOO is submitted, it comes in with the dates and recieves a status of RatE. At this point the TOO is not usable. Closed TOO which is not approved is not reverted to waiting state after DR Planned End Date is passed If the TSP that submtted the TOO does not take the TOO and the Designated Resource outage Planned End passes, the TOO is not changing back to the waiting (Stage 1) state. Closed Can't add a supporting note to a Group TOO that has been extended to ack the warning message The user can enter Supporting Information on an extended Group Transmission Opportunity Outage that has been extended.

10. http://nodal.ercot.com 10 Environment Report: Known Issues Newly Closed Issues (continued): StatusIssueDescription Closed OS EWS: Group outage with a single piece of equipment error Using EWS If a MP send a Group Outage with only one piece of equipment, they are getting the error message "> ERROR One or more outages in this request failed during processing within the OS system, but the OS system did not respond with a descriptive error. Please contact ERCOT Operations for more information. " but the system does create the outage. Closed OS UI timeout needs a more relevant page display when the OS UI times-out The OS UI is being directed to a default page that tells them the authorization has failed and to call ERCOT Closed Equipment missing from the equipment list and Primary and Secondary phone numbers may be incorrect. When trying to enter an outage some equipment may not be available and the Primary and Secondary Phone number may be incorrect. Closed User cannot add a supporting notes before the Actual End has been submitted. When an outage is extended a supporting note is required. the user cannot enter this note until the Actual End date has been entered. Closed Operating Company Field - Displays companies that do not have equipment When a TSP is filtering for other companies outages or entering outages that another TSP operates, the TSP will see Companies that do not have equipment as well as ones that do. Closed OS Reports Planned vs. Actual Transmission Outage Annual Statistics Report (NP3-538 ER) - Update cover sheetUpdate the cover sheet to include the formula.

11. http://nodal.ercot.com 11 Q&A Q&A / Open Forum