1. September 24, 2007 – Page 1 ColumbiaGrid Puget Sound Area Study Team Outage Scheduling Challenges Summer 2007 and Beyond Seattle City Light

2. September 24, 2007 – Page 2 Planning Assumption: All Lines in Service? Planning base case assumption of All Lines In Service (ALIS) may be creating serious challenges currently experienced in the operating horizonPlanning base case assumption of All Lines In Service (ALIS) may be creating serious challenges currently experienced in the operating horizon Planning assumptions may not reflect operating realitiesPlanning assumptions may not reflect operating realities –Operating state of the system may be N-2, N-3, or N-X for extended periods of time due to planned outages –The need for maintenance scheduling cannot be ignored in planning studies –Increasing frequency and duration of maintenance outages –Overlapping outages are common Operating staff assume responsibility for operating a system that is seldom in ALIS state.Operating staff assume responsibility for operating a system that is seldom in ALIS state.

3. September 24, 2007 – Page 3 Summer 07 ALIS S-N Nomogram

4. September 24, 2007 – Page 4 June S-N Nomograms Outage 140R2 85 F 70 F

5. September 24, 2007 – Page 5 June S-N Nomogram Limits

6. September 24, 2007 – Page 6 ALIS WNI N-S Nomogram

7. September 24, 2007 – Page 7 July 9 N-S Nomogram Outage 204 85F

8. September 24, 2007 – Page 8 July 9 N-S Nomogram Outage 204R3 85F

9. September 24, 2007 – Page 9 July N-S Nomogram Limits

10. September 24, 2007 – Page 10 Are too many elements simultaneously OPEN? Level of detail being consideredLevel of detail being considered –Old rules of thumb cannot be used –Granularity of operating cases far exceeds planning models – esp. contingency defs. –Contingency definitions result in many elements being O/S simultaneously –New NWPP COS will help and hurt BFRs that take out multiple facilities should be addressed immediatelyBFRs that take out multiple facilities should be addressed immediately

11. September 24, 2007 – Page 11 Planning for Scheduled Outages How should a realistic set of outage scenarios be developed for a planning case?How should a realistic set of outage scenarios be developed for a planning case? –Develop a Monte Carlo type approach –Use historical maintenance outage schedules –Extend outage planning process milestones –Select a outage group based on known maintenance needs, age (Iowa curves), other. Outage schedule will only be good for one-year into the future max.Outage schedule will only be good for one-year into the future max.

12. September 24, 2007 – Page 12 Study Methods WECC Basecase (ALIS)WECC Basecase (ALIS) Modifications to reflect updated loads, generation patterns, ratingsModifications to reflect updated loads, generation patterns, ratings Outage schedules overlaidOutage schedules overlaid Contingency Definitions:Contingency Definitions: –e.g. BFR at MV#3 ATC Tool and Nomogram StudiesATC Tool and Nomogram Studies

13. September 24, 2007 – Page 13 Future Outage Schedules Drivers: Need to Restore RatingsNeed to Restore Ratings Changes to Relay Protection SystemsChanges to Relay Protection Systems Age of Transmission FacilitiesAge of Transmission Facilities WSDOT RequirementsWSDOT RequirementsApproaches: Repositioning under-built circuitsRepositioning under-built circuits Increasing Physical ClearanceIncreasing Physical Clearance RetensioningRetensioning ReconductoringReconductoring Tower ReplacementsTower Replacements –Sometimes Double-Circuit towers!

14. September 24, 2007 – Page 14 Labor Issues Resource CommitmentResource Commitment –Rescheduling crews is not always an option OvertimeOvertime –Outage schedules are requiring more work during LLH periods –During outages, additional crews must be available to address a contingency

15. September 24, 2007 – Page 15 Mitigation Measures Risk of implementing mitigation measuresRisk of implementing mitigation measures –Load shedding –RAS arming –Sectionalizing transmission –Distribution load transfers Mass Bank 17 has been in service during entire summerMass Bank 17 has been in service during entire summer –Transformer configuration is not in normal state –Flow on MA-BR cables is affected by state of Mass transformer banks –SCL Downtown Network more vulnerable to certain contingency events

16. September 24, 2007 – Page 16 October Outlook BO-UN and BO-NO: to be taken out simultaneouslyBO-UN and BO-NO: to be taken out simultaneously –BO-NO is not on the NWPP critical facilities list (but BPA is aware of the outage) Limiting facility may be in SCL service areaLimiting facility may be in SCL service area Other: BO-SK, SE-HO-BO, TAC-RAV 500Other: BO-SK, SE-HO-BO, TAC-RAV 500 See BPA outage plan for October 2007See BPA outage plan for October 2007

17. September 24, 2007 – Page 17 Other SCL Outages (next summer and beyond) Viaduct cable relocationViaduct cable relocation 115 kV tower replacements115 kV tower replacements SLU substation = extended EP-BR outageSLU substation = extended EP-BR outage BO-UN & BO-VI scheduled for next year.BO-UN & BO-VI scheduled for next year. BO-SH 1 & 2 capacity restorationBO-SH 1 & 2 capacity restoration –Increase clearance -> increase rating. UN-BR looking at options to increase clearance to restore capacityUN-BR looking at options to increase clearance to restore capacity

18. September 24, 2007 – Page 18 Summary Summer 2007 nomograms are a wake-up call – Fall and Winter may also be adverseSummer 2007 nomograms are a wake-up call – Fall and Winter may also be adverse Transmission system is seldom in ALIS stateTransmission system is seldom in ALIS state Planning studies need to more closely reflect probable operating statesPlanning studies need to more closely reflect probable operating states Future outages are necessary to maintain existing system capabilityFuture outages are necessary to maintain existing system capability Work-arounds and mitigation plans are not always feasibleWork-arounds and mitigation plans are not always feasible