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SW Oregon Coast Reinforcement Project

Background. The southwest Oregon load service area extends from Fairview to Brookings, serving the City of Bandon, Coos Currey, and PAC's Isthmus and Coquille feeders. The area is served by two 230kV and one 115kV lines from Alvey, Dixonville, and Reedsport respectively. The loads served south o

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SW Oregon Coast Reinforcement Project

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    1. SW Oregon Coast Reinforcement Project Anthony Radcliff Transmission Planning Bonneville Power Administration

    2. Background The southwest Oregon load service area extends from Fairview to Brookings, serving the City of Bandon, Coos Currey, and PAC’s Isthmus and Coquille feeders. The area is served by two 230kV and one 115kV lines from Alvey, Dixonville, and Reedsport respectively. The loads served south of Fairview are served with looped service via a 230kV line from Fairview to Rogue and a 115kV line from Bandon to Rogue.

    3. Challenges The weakest portion of the system are both radial lines served from Rogue down the southern Oregon coast to Brookings and Harbor on Coos Currey’s system. The southern Oregon coast is a winter peaking system with the worst contingency being the loss of the Fairview-Rogue 230kV line. The contingency possibly causes voltage instability, depending on the load level, rather than thermal limit overloads. Previous studies recommended constructing a 46 mile long 115kV from Bandon to Rogue to mitigate the voltage instability problems.

    4. South of Fairview Service Area

    5. Reactive Power Margin Bottom of the QV Curve = 4MVARs 90% voltage = 1MVAR Initial point violates BPA’s voltage criteria Maximum switch-able (8% voltage swing) = 7MVARs….too small!

    6. Original Plan of Service: Transmission Line New 46 mile long Bandon-Rogue 115kV line constructed to 230kV specification for later upgrade 1.1in ACSRTW Rogue conductor was chosen Initial estimates: Line, Towers, etc… = $25M plus Land/Environmental Survey = $3.6M Land/New right of way = $$$$$ Performance Line could be put into service between 2008-2010 Voltage support would be needed by the 2015 predicted load level Options available at that time: Upgrade to 230kV Requires transformer at Bandon ($5M-$7M) SVC at Rogue Only small amounts of reactive can be switched without large voltage changes

    7. Other Considerations on the New Transmission Line Light loading conditions Area experiences high voltages under light loading conditions that may damage equipment Adding another line may aggravate high voltages The new line will place other lines below their surge impedance loading, causing them to produce more reactive power than they absorb More available reactive power will boost voltages Area is under light loading conditions most of the time Conductor size A larger conductor than necessary (thermal loading) was specified due to the voltage support required Adds to the cost of the project

    8. Other Options Considered The drawbacks of the new line project caused another round of studies aimed at finding a non-transmission line solution Main deterrent was price…. $35M to $45M Other options: Multiple switched shunt capacitor groups Would require many due to switching sensitivities and coordination would be difficult Series capacitors Tapped transmission line would make placement difficult due to voltage profile caused by series capacitor group Short transmission lines (distance in km should exceed voltage in kV) Static VAR Compensator (SVC) Continuous reactive power output (switching sensitivities no longer a problem) Can mitigate light loading/high voltage issues Supports voltages to the predicted 2016 load level, outperforming the transmission line The next limitation on the system is the thermal limit of the Bandon-Rogue 115kV line

    9. Static VAR Compensator The Static VAR Compensator (SVC) became Planning’s preferred plan of service of the alternates to the new transmission line. SVC Specification: 40MVARs inductive/45MVARs capacitive Initial estimate for a turnkey device was $5M An additional $2M in site development, communications, and high voltage connections Pros Solves voltage instability issue Delays new line construction nine years Cost less than a new transmission line Mitigates high voltage issues Could be on-line in 14 months Cons Maintenance: cooling systems, remote location, and untrained personnel New line may be required in the future The studies showed that if the load continued to grow, both projects would be needed eventually

    10. Factors Considered in Project Selection Matrix Team A group of BPA employees consisting of engineers and financial analyst assigned to evaluate projects and give their recommendation to management Risk mapping Financial Agency Target Legal Impacts Environmental External Stakeholders People and Processes Reliability Each area is graded on severity of impact Can be used to compare competing projects The line and the SVC would score the same in most categories except Financial Agency Target and Environmental impacts New line cost considerably more and would require land in possibly sensitive areas

    11. South Oregon Coast

    12. Geographical Map

    13. System Map

    14. South of Fairview Service Area

    15. System One Line

    16. Project Timeline By Need Date

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