1. ACE Diversity Interchange (ADI)
Discussion
OC Meeting
Marina Del Ray, CA
Mark C. Willis
SMUD
October 30-31, 2008

2. Current Operation Two ADI “Bubbles” within WECC
NW Bubble with seven participants
SW Bubble with five participants
Each participating BA limited to 30 MW ACE deviation
Suspended for concerns about system reliability
BA operator falls back to original ACE

3. Current = 30 MW
NW Bubble
7 BAs
ACE=0
SW Bubble
5 BAs
ACE=0

4. Proposed Operation One ADI “Bubble” within WECC
Proposal for each participating BA limited to 50 MW ACE deviation, but starting with 30 MW
One/Two Bubble operation with 14 entities will be operational by 11/1/08
All entities scheduled to participate by January 2009r
Again, suspended for concerns about system reliability
BA operator falls back to own ACE

5. WECC Bubble NW Bubble SW Bubble
Current = 30 MW
NW Bubble
ACE=0
7 BAs
“TOT2”
150
40 MW
ACE=+150
SW Bubble
5 BAs
110 MW
150
“COI”
ACE=-150

6. Reliability Concerns (1)
Two “bubble” system
No concerns for two “bubble” system currently in place

7. Reliability Concerns (2)
One “bubble” system concerns:
Oversight responsibility of entire WECC transmission system
ADI Participants unaware of all transmission impacts/conditions between NW and SW bubbles
Within California, multiple constrained 500 kV paths, many of which are dynamically rated in real-time operations, both N-S and S-N
Separation of unscheduled flow versus ADI on USF qualified WECC Paths, such as COI
SOL (OTC) mitigation impacted by ADI flows – scheduled and/or forced outages and resulting mitigation requirements
Increased COI SOL (OTC) mitigation requirements

8. Northern California Transmission Usage Concerns
Usage of California-Oregon Transmission Project (COTP), as part of the California-Oregon Intertie (COI)
Impacts multiple COI owners, including TANC, WASN, and PG&E
Unscheduled transfer of energy between BAs across various TO/TOP systems

9. Recommendations
Open the ADI Operating Group to all interested WECC entities
Form a Task Force under Operating Practices Subcommittee (OPS) as assigned by the Operating Committee to study and evaluate reliability impact to WECC
Transmission Usage – Mitigation of “take of transmission”

10. Questions/Discussion

11. Talking Points (1)
Parties in California, which are not participating, are not held harmless due to significant flow of ADI on the 500 kV system between the Northwest and Southwest, during “one bubble” operation, resulting in usage of other’s transmission through unscheduled transfers of energy between participating Balancing Authorities (BAs).

12. Talking Points (2)
Multiple WECC 500 kV paths within California are impacted both North-to-South and South-to-North during “one bubble” operation, resulting in a potential for unreliable operation and mitigation of SOL overloads, since the ADI participants are not the Transmission Operators (TOPs) of many of these paths. These WECC 500 kV paths include COI[1], Path 15, Path 26, West-of-River, and East-of-River[2], of which many of the System Operating Limits (SOLs) are dynamically determined in real-time by the respective TOP.
[1] BPA will be monitoring the COI SOL in real-time to change ADI operation from “one bubble” to “two bubble.”
[2] APS is the path operator for East-of-River.