Western Interconnection 2006 Congestion Assessment Study

1. Western Interconnection 2006 Congestion Assessment Study Prepared by the Western Congestion Analysis Task Force May 08, 2006

2. Western Interconnection2006 Congestion Study- DOE Task 3 - • 2008 Modeling Study • 2015 Modeling Study • 2015 Planned Resource Development (IRPs and RPS) • W.I. Historical Path Usage Studies – 1999 thru 2005 • Physical congestion • Commercial congestion

3. WCATF Modeling StudiesABB Gridview Model • Model uses WECC 2005 L&R load forecast, modified with NPCC data for the NW, RMATS load forecasts for the Rocky Mtn area and the latest CEC load forecast for California • Hourly load shapes were developed using FERC 714 • Incremental transmission was added to a WECC 2008 case to represent 2015 network topology • WECC path ratings were used, modified as necessary to more closely represent operating experience. Path nomograms were modeled. • Gridview has the ability to model losses, wheeling rates and forced outages, however these were not modeled in the 2015 study. (this will be pursued in the future)– Losses were included in the load projections. Loss sensitivity was investigated in the 2008 study. • Resources • Modeled unit commitment with actual data if known; generic data if unknown • Incremental resources reflect utility IRPs and state RPS standards • Unit forced outage rates are modeled, using EIA data • Modeled Startup costs, ramp rates and variable O&M costs, gas prices of $5, $7 and $9. • Hydro and Wind are hard wired into the model, using data obtained for the major western river systems and from the National Renewable Energy Lab.

4. WECC Transmission Paths Definition & Rating • All WECC CatalogedPaths are modeled, representing potentially constrained W.I. Paths, including Unscheduled (Loop) Flow Qualified Paths and OTC Policy Group paths. They represent all the significant paths in the W.I. • A Path may represent a single line or combination of parallel linesfrom one area or a combination of areas to another area or combination of areas • A Path may be between Control Areas or internal to a Control Area. • Paths are defined based upon extensive planning studies and operating experience. They are well documented through a formal process.

5. WECC Transmission Paths (Cont.) • Ratings are established thru an open process described in the WECC “Procedures for Regional Planning Project Review and Rating Transmission Facilities” document. • Ratings are documented in the WECC Path Rating Catalog • Ratings include both non- simultaneous and simultaneous limits, including development of nomograms • All ratings are established applying NERC/WECC reliability criteria; the path must be able to withstand an outage while operating at rated capacity • Ratings in the West are determined by the more restrictive of applicable steady state or contingency limits. These include transient, voltage stability and thermal limits. • 67 existing WECC paths are currently rated

6. WECC Transmission Paths (Cont.) • The WECC Operating Transfer Capability (OTC) Policy Committee reviews seasonal operating ratings for selected critical paths. • Bottom Line: • TO MAINTAIN RELIABLE OPERATION, WESTERN PATH RATINGS ARE OFTEN BASED UPON STABILITY LIMITS WHICH MAY BE MORE LIMITING THAN THE THERMAL LIMITS THAT TYPICALLY LIMIT EASTERN PATHS. THIS IS PRIMARILY BECAUSE OF LONG TRANSMISSION DISTANCES IN THE WEST. • All production cost modeling in the West (SSG-WI, RMATS, STEP & CDEAC studies) recognize OTC limits on all WECC paths and on all “internal” lines, but not the “day to day” operational limits that are based upon prevailing system conditions.

7. Understanding Western Path Flows Measurement of Transfer Capacity Example - California Oregon Intertie (COI) Path Ratings U75, U90 and U(Limit) Thermal rating (N-0 = 10,500 MW) (N-1 = 6000 MW) U75 – % of time flow exceeds 75% of OTC (3,600 MW for COI) WECC Contingency Rating (N-1, N-2 = 4,800 MW) WECC/NERC Criteria U90 - % of time flow exceeds 90% of OTC (4,320 MW for COI) % of Time U(Limit) - % of time flow reaches 100% of OTC (4,800 MW for COI) 75% 90% 100% % of OTC

8. Western Interconnect Transmission Paths Northwest to Canada Alberta to BC Monroe-Echo Lake West of Hatwai Cross Cascades North Paul-Raver North of Hanford Paul-Allston Montana to NW North of John Day Allston-Keeler West of Broadview West of MCNary West of Colstrip Cross Cascades South NW to Idaho Montana Southease Idaho-Montana Borah West TOT 4B PDCI COI TOT 4A Reno-Alturas Idaho-Sierra Bridger West Path C Intermountain-Mona TOT 1A Bonanza West TOT 3 IPP DC TOT 5 Midway-Los Banos TOT 2A TOT 2C WOR Southwest of Four Corners Northern-Southern California EOR Cholla-Pinnacle Peak NOTE: For clarity, not all WECC Rated Paths are shown. SDG&E-Comision Federal de Electicidad

9. NOTE: There are 67 WECC Rated Paths. Not all numbers are used.

10. Part 12008 Modeling Study

14. Notes for Reviewing the 2008 Study Results • Yellow Paths in the Tables are WECC Rated Paths • White Paths in the Tables are other monitored lines, mostly located within WECC Rated Paths • Study Metrics – U75, U90, U(Limit), Congestion Rent, Shadow Price averaged over 8760 hours, Shadow Price averaged over the “binding (or limit)” hours • Metrics used to Identify Congestion Areas – Binding Hours Shadow Price, U75 and U90 • The following Paths may be considered by their owners to be “dedicated” facilities, planned and designed to integrate or deliver specified resources to load: (These were designed to be high usage paths and may not be considered congested) • Path 27 – Intermountain Power Project (IPP) DC Line • Path 19 – West of Bridger

15. Definitions • U(Limit) = Annual Hours operating at the Path’s Limit • U75 & U90 = Hours of the year a path operates above 75% or 90% of the Path Limit. Note that in the historical path studies, U75 is sometimes the maximum seasonal value over the years studied. • Congestion Rent = Average Hourly Shadow Price times Path Flow on that Hour, summed for the year • Average Shadow Price = Average of the hourly Shadow Prices, averaged over 8760 Hours • Binding Hour Average Shadow Price = Average Shadow Price, averaged over the number of hours the path is at its limit.

16. 2008Path Usage StudyResults $5, $7 (reference) and $9 Gas Price

26. 2008 Path Shadow PricesResults

31. 2008Alternative Ranking MethodsCongested Areas/Paths

32. Evaluation of Alternative Ranking Methodologies • Five alternative Congestion Ranking Methods were applied to the W.I. 2008 Study results: • U90 • U75 • Shadow Price (binding hours) • Average of 9 metrics • Average of 9 metrics (modified method) • Conclusion - - Ranking methodology results vary considerably, therefore identified W.I. Congestion Areas are grouped geographically and not ranked

33. Five Alternative Ranking Methods • U90 • A usage based ranking • Paths were ranked using U90 at $7 gas • U75 • A usage based ranking • Paths were ranked using U75 at $7 gas • Shadow Price • An economic based ranking • Paths were ranked using “binding hours shadow price” at $7 gas • Averaging Method • A combined usage and economic based ranking • Paths were ranked by (1) calculating the path’s subranking for each of 9 categories (U90, U75, shadow price - - $5, $7, and $9 gas) and (2) calculating the average of these 9 subrankings. This value was then used to rank the paths. • Averaging Method (modified) • A combined usage and economic based ranking • Same as Method 4, however it was only applied to paths that ranked in the “top ten” in at least one of the 9 subranking categories. • This method defines a congestion grouping and assures that all paths that ranked high in at least one category are included.

36. 2008Loss Comparison StudyAverage vs. Incremental Transmission Losses

37. 2008 Study - Loss Comparison • Task 3 Studies used Average losses to be comparable to the Eastern Interconnection studies. • A loss comparison study was run as part of the 2008 W.I. study. For comparison, transmission line losses were modeled as both Average Losses (included as a fixed amount in the load) and as Incremental Losses (line losses vary as the square of the line flow. • Results are preliminary and need further analysis • Preliminary results indicate the way line losses are modeled can have a significant impact on congestion. • Modeling incremental line losses generally reduces congestion, often by a significant amount. • A comparison is made between modeled path flows with average and incremental losses and observed historical flows

42. Part 22015 Modeling Study

43. SSG-WI Path LimitsWECC Catalogue Operating Limits & Adjustments Made by SSG-WI(xxx - Rating used in 2015 SSG-WI study, (xxx) – current WECC rating if different)

44. 2015 Resource Assumptions Modeled Utility Integrated Resource Plans (IRP) and State Renewable Portfolio Standards (RPS)

45. Key Caveats • Transmission congestion found in modeling is primarily driven by gas prices, hydro conditions and assumptions about location of generation resources in 2015 • Actual 2015 generation additions will evolve from those assumed in the study based on LSE preferences and state policies

46. 2015 Resources By Area and Fuel Type

49. 2015 Study Results Path Usage Path Economics

50. Key Caveats • High Flow Rankings do not necessarily imply Congested Paths. Some paths in the West have high flows because the path’s primary function is to transmit generation to a specific load area. The IPP DC Line and Bridger West paths are typical examples. • Results are highly dependent upon gas prices, hydro conditions and location of future resources.