1. ColumbiaGrid Puget Sound Area Study Team
Seattle City Light
ColumbiaGrid Puget Sound Area Study Team
Outage Scheduling Challenges
Summer 2007 and Beyond

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 horizon
Planning 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.

3. Summer 07 ALIS S-N Nomogram

4. June S-N Nomograms 70 F 85 F Outage 140R2
Outage 140R2: Tacoma - Raver #1&2 500kV, Christopher - O'Brien Tap of Tacoma - Covington #2 230kV, Duwamish - Delridge 230kV,University - Broad St. 115kV, Sedro Woolley 230/115kV Bank O/S

5. June S-N Nomogram Limits

6. ALIS WNI N-S Nomogram
85 F
North to South

7. July 9 N-S Nomogram Outage 204 85F
Outage 204: University-Broad St #1 115kV, Tacoma-Raver #1 & #2 500kV & Chief Joseph-Snohomish #4 345kV Lines & Bellingham 230/115kV Transformer Bank #1 O/S

8. July 9 N-S Nomogram Outage 204R3 85F
Outage 204R3: Tacoma-Raver #1&2, Chief Jo-Snoh #4, University-Broad St, Sedro W 230/115 Bank, Bellingham 230/115 Bank #1 & Bothell 230/115 Bank O/S; All Massachusetts 230/115 Banks I/S

9. July N-S Nomogram Limits

10. Are too many elements simultaneously OPEN?
Level 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 immediately

11. Planning for Scheduled Outages
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.

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

13. Future Outage Schedules
Drivers:
Need to Restore Ratings
Changes to Relay Protection Systems
Age of Transmission Facilities
WSDOT Requirements
Approaches:
Repositioning under-built circuits
Increasing Physical Clearance
Retensioning
Reconductoring
Tower Replacements
Sometimes Double-Circuit towers!

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

15. Mitigation Measures Risk of implementing mitigation measures
Load shedding
RAS arming
Sectionalizing transmission
Distribution load transfers
Mass 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. October Outlook BO-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 area
Other: BO-SK, SE-HO-BO, TAC-RAV 500
See BPA outage plan for October 2007

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

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