Pinto Third Phase Shifter Technical Review of Impacts to Existing Qualified Paths

1. Pinto Third Phase ShifterTechnical Review of Impacts to Existing Qualified Paths Unscheduled Flow Administrative Subcommittee Craig Quist, PE Transmission Planning January 20, 2016

2. Overview • The Pinto third phase shifting transformer (PST) is owned and operated by PacifiCorp and will be included in the updated qualification of preexisting compensation for coordinated operation per the requirements of the USF Mitigation Criteria methodology • While the Pinto new PST is key to increasing the Path 78: TOT 2B1 (Pinto – Four Corners) path rating, addition of the PST will improve reliability of the Pinto facility; however, only minor impacts on major loop flow on the Western Interconnection will be evident

3. TOT Path – Historical Perspective SCE Question: What was TOT2 fifteen – twenty years ago? At the moment, it is four different distinct paths in the path rating catalog. I was wondering if it was one path at one time? PacifiCorp Response: Thanks for the enquiry concerning the TOT 2 path designation in the WECC Path Rating Catalog • The definition of the TOT (total) path designations (TOT 1 thru 7) had their initial genesis in to mid to late 1980 time-frame when WAPA (Bob Easton) recommended that transmission paths in Colorado, Wyoming and Utah that affected WAPA be defined and rated • Through this effort, the TOT 2 transmission paths were defined those paths that crossed the WECC NE/SE cutplane, which cuts across southern Utah and southern Colorado, with TOT 2A being defined as the Colorado-New Mexico path and TOT 2B the Utah-Arizona/New Mexico path.  [With only few exceptions, all transmission lines that cross TOT 2 are phase shifted to control WECC major loop flow.]

4. TOT Path – Historical Perspective (cont.) • With the addition of the Sigurd – Red Butte – Harry Allen 345 kV transmission line in 1990, the TOT 2C transmission path (RB-HA) was added to the TOT 2 path designation and the TOT 2B transmission path was split into TOT 2B1 (Pinto-Four Corners) and TOT 2B2 (Sigurd – Glen Canyon) • Due to possible interaction between the TOT 2B1, 2B2 and 2C transmission paths, path ratings of these paths are considered simultaneously with each other (n2s – maximum, or s2n – maximum) when evaluating possible interaction with other WECC transmission paths

5. TOT 2B1, TOT2B2, and TOT2C Cut-Planes

6. Current Qualified Controllable Devices • Inadvertent loop flow on the Western Interconnection is currently controlled by ten PSTs at five key locations: • Path 31 (TOT 2A): Shiprock and San Juan, New Mexico • Walsenburg-Gladstone 230 kV line: Gladstone, New Mexico • Paths 78/79 (TOT 2B1/2B2): Pinto (two PSTs) and Sigurd, Utah • Path 35 (TOT 2C): Harry Allen (two PSTs), Nevada • Path 80 (Montana Southeast): Billings and Crossover, Montana

7. Western Interconnection Loop Flow Control

8. Pinto Third PST Summary • Thermal rating of third PST is 400 MVA (normal) • Angle range is +74.5 degrees • Pinto new PST is 100% owned and operated by PacifiCorp • The new PST at Pinto will help increase the path rating of the WECC Path 78 (TOT 2B1) • The TOT 2B1 path is currently rated at 600 MW bi-directional. With addition of the new phase shifting transformer the TOT 2B1 path rating is expected to be 700 MW northbound and 626-647 MW southbound (interaction with Pinto area wind farm)

9. Pinto PST – Transport Across New Mexico, Arizona, Utah MONTICELLO, San Juan County (11/2/2015)— A transformer weighing nearly 1 million pounds will arrive at the Monticello fairgrounds Monday after a week of traveling by truck at speeds of 3-10 mph through New Mexico, Arizona and Utah. The transformer — measuring 25 feet wide and 415 feet long on its trailer — made its way from China to Houston by boat, from Houston to New Mexico by train, and is finishing its journey by slow-moving truck. In total, the load weighs 1.8 million pounds, according to the Arizona Department of Transportation. The PacifiCorp, Rocky Mountain Power-owned piece of equipment started its highway trek Monday, Oct. 26 and will arrive on Highway 191 at Monticello's fairgrounds around noon, the project manager said. In two weeks, the second, smaller piece of equipment will arrive and the pieces will be transported to the Monticello substation for installation in the wind generator farm. Law enforcement officials, including Utah Highway Patrol, escorted the transformer along the way and between 15 and 20 vehicles were involved in its transportation. The load was one of the heaviest ever transported on Arizona state highways, according to ADOT. [KSL-TV5, Salt Lake City, Utah]

10. Pinto PST – Transport Across New Mexico, Arizona, Utah

11. Pinto Third PST – Will Improved Reliability • Previously, loss of one PST, both PSTs would need to be bypassed • With the added PST, for the loss of one PST, two PSTs will be available for control

12. Pinto Third PST – Impact on WECC Paths TOT 2B1 Path Rating studies have demonstrated, by modeling the Pinto third PST: • A simultaneous interaction between TOT 2B1 Path and IPPDC line or IPP Net Imports is identified and necessary nomogram will be implemented as required • A simultaneous interaction between TOT 2B1 and TOT 2C (Southwest Utah to Southern Nevada) path was identified and necessary nomogram will be implemented • No significant interaction was identified between TOT 2B1 path and • Path 22 (Southwest of Four Corners), • Path 23 (Four Corners 345/500 Qualified Path), • Path 30 (TOT 1A, Extreme Northwest Colorado), • Path 31 (TOT 2A, Extreme Southwest Colorado), • Path 32 (Pavant-Gonder 230 kV; Intermountain-Gonder 230 kV), and • Path 33 (Bonanza West, Northeast Utah to Central Utah)

13. Pinto Third PST – Minor Impacts on Loop Flow Spreadsheets have been developed to show the incremental flow changes for PST tap changes at Pinto.  On the sheet below, the table illustrates PST #4 in the lead and PST #5 following.  A one tap disagreement results in a flow difference between PST #4 & #5 of ~113 MW.  The net change in flow on the Pinto-Four Corners 345 kV line is ~24 MW per tap step with the two PSTs.  Note: Existing Pinto PSTs are identified as XFMR #4 and #5; the new PST will be XFMR #6

14. Pinto Third PST – Minor Impacts on Loop Flow (cont.) On the sheet below, the table illustrates PST #6 in the lead and PST #5 and then PST #4 following.  A one tap disagreement results in a range of differences.  The net change in flow on the Pinto-Four Corners 345 kV line is ~25 MW per tap step with all three PSTs.  The impedance of PST #6 was specified such that the PSTs will load in proportion to the MVA capability of three PSTs (315 MVA, 315 MVA, and 400 MVA respectively).

15. Pinto PST Performance Table – Comparison Two PSTs Three PSTs 8.8 6.2 3.8

16. Pinto Third PST – Tap Adjustment Findings • The net change in flow on the Pinto-Four Corners 345 kV line is ~24 MW per tap step with two PSTs • The net change in flow on the Pinto-Four Corners 345 kV line is ~25 MW per tap step with all three PSTs • Studies demonstrate that the impedance of the new PST was properly specified such that the PSTs will load in proportion to the MVA capability of three PSTs (315 MVA, 315 MVA, and 400 MVA, respectively) • Addition of Pinto new PST will reduce the overall impedance between Huntington and Four Corners, resulting in an increase in TOT 2B1 path flows a few percentage, when PSTs are placed on the neutral tap • The impacts of this increase in line flows on the TOT 2B1 path will be negligible on Western Interconnection major loop flow

17. Impacts of the Pinto Third PST on the Western Interconnection • PSTs on the TOT 2 paths (southern Nevada, Utah, Colorado) effectively control major loop flow • Status of individual PSTs can effect overall control performance • Major loop flow control performance is measured at COI COI TOT 2

18. TOT 2B1 (Pinto PST) Impacts on COI • During TOT 2B1 outage conditions, ~30% of the flows will be seen on COI • The Pinto PSTs provide the same level of major loop flow control • Likewise, increased TOT 2B1 path flows by 6 MW (Pinto PSTs on neutral tap) due to adding the third PST at Pinto will only add ~2 MW to COI flows

19. Pinto Third PST – Impacts on System Performance • Double-pole outage of the IPPDC line will have the most significantly impacts to southeast Utah transmission system • Addition of the Pinto new PST will maintain SE Utah system performance while supporting higher transfers

20. Conclusions The Pinto third PST: • Will be included in the updated qualification of preexisting compensation for coordinated operation per the requirements of the USF Mitigation Criteria methodology, • Is key to increasing the Path 78: TOT 2B1 (Pinto – Four Corners) path rating, • Will maintain local system performance while improving reliability of the Pinto facility, and • Will have only minor impacts on major loop flow on the Western Interconnection

21. Questions