Dakotas Wind Transmission Study South Dakota Legislative Briefing Pierre, South Dakota January 18, 2006 Edward P. Weber Transmission System Planning Manager Upper Great Plains Region

2 Overview Study Background Study Parameters Study Results Future Work

3 Study Background Congress provided funding for Western to perform a transmission study on the placement of 500 MW of wind energy in North Dakota and South Dakota The Dakotas lead the nation in potential wind resources Already an exporting region; transmission is limited by both stability and thermal loading

4 Dakotas Wind Transmission Study Objectives Perform transmission studies on placing 500 MW of wind power in North and South Dakota Recognize and build upon prior related technical work, coordinate with current work Solicit and incorporate public comments Produce meaningful, broadly supported results through a technically rigorous, inclusive study process

5 Study Parameters – Four Primary Tasks 1.Analyze non-firm transmission potential relative to new wind generation 2.Assess potential of transmission technologies relative to new wind generation 3.Study interconnection of new wind generation 4.Study the delivery to market of new wind generation

6 Task 1: Analyze Non-Firm Transmission Potential Existing total transfer capability across the major paths in the Dakotas is already reserved under long-term contracts Scheduled amount of capacity is often less than the total amount, leaving unused capacity in many hours of the year Study the possibility of delivering wind energy through long-term, non-firm access, with curtailment during critical periods

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8 Task 1 Contd: Analyze Non-Firm Transmission Potential Three key corridors studied: - North Dakota Export Boundary – 17 lines (115, 230, 345 kV) - Watertown-to-Granite Falls 230 kV - Group of 8 lines between Ft. Thompson & Ft Randall Evaluate and compare committed vs actual usage across each corridor using historical data & modeled projected data Evaluate & develop wind power production profiles for the Dakotas Evaluate & compare transmission usage and wind generation profiles using historical data Develop annual flow duration curves, assess the opportunity to deliver non-firm wind energy Run sensitivity cases

9 Task 2: Analyze Potential of Transmission Technologies Study technology-based solutions that can increase the use of existing transmission lines Technologies studied include: - Static var compensation - Series compensation - Phase-shifting - Dynamic line ratings - Reconductoring with new conductor

10 Task 3: Study Interconnection of New Wind Generation Evaluate seven wind generation zones for interconnection - Developed from public comments, wind resource maps, the Western interconnection queue, tribal projects and developer projects Determine the local impacts of new wind generation for each site at four wind generation levels of 50, 150, 250, and 500 megawatts Study impacts including steady state power flow analysis, constrained interface analysis, short circuit analysis and dynamic stability analysis

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12 Task 4: Study the Delivery to Market of New Wind Generation Perform aggregate delivery studies on the four most favorable interconnection zones in Task 3 Develop several delivery scenarios for the new wind power based upon markets both inside and outside of the Dakotas Identify the incremental transmission delivery capability of each zone along with the necessary transmission improvements for each level of generation; Complete both steady state and stability analysis

13 Study Results: Task 1 Transmission constraint evaluation - Monitored NDEX limit - Monitored limit on each line in each interface - NDEX - Ft Thompson - Watertown

14 Flow Data from Western

15 Benchmark NDEX Flow Data from Gridview Simulation

16 Measured NDEX Flows Minus GridView NDEX Flows

17 Results from Gridview Analysis for 2003 (Low Hydro) For Low Hydro, NDEX was limiting for: 1.14 hours for Garrison site 2.3 hours for Ellendale site 3.9 hours for Pickert site Ft Thompson Interface not limiting Watertown Interface not limiting For High Hydro, NDEX was limiting for: hours for Garrison site 2.2 hours for Ellendale site Ft Thompson Interface not limiting Watertown Interface not limiting

18 Study Results: Task 2 Transmission Enhancements For Steady-State Improvements Add conventional series capacitors Add phase-shifting transformers Re-conductor transmission lines Dynamic transmission line ratings

19 Study Results – Task 2 Transmission Enhancements For Steady-State Improvements Re-conductor Transmission Lines Several newer conductors: Aluminum Conductor Steel supported (ACSS) Aluminum Conductor Steel Supported / Trapezoidal Wire (ACSS/TW) Aluminum Conductor Composite Reinforced ACCR) All Aluminum Alloy Conductors (AAAC)

20 Study Results – Task 2 Transmission Enhancements For Steady- State Re-conductor Transmission Lines

21 Study Results – Task 2 Transmission Enhancements Contd Dynamic Transmission Line Ratings Wind generation starts at about 3.5 m/s Max wind generation from 12 m/s to 25 m/s With max generation at 12 m/s, assume nearby lines have 33% or 4 m/s wind Wind angle to line is 15 degrees then wind correction factor is m/s x 0.53 = 2.12 m/s Convection cooling increases 187% over 0.61 m/s in conductor tables Convection cooling is > 85% of total cooling so conductor dynamic rating will increase upto 170%

22 Study Results – Task 3-4 Task 3 - Interconnection studies for each of the seven sites - Determined local system requirements Task 4 - Analyzed transfer capability - Analyzed regional stability performance

23 Study Results – Task 3 System interconnections for each 500 MW scenario Scenario 1:Garrison 230-kV bus Scenario 2:New substation on the Leland Olds-Groton 345-kV line near Ellendale Scenario 3:Pickert 230-kV bus Scenario 4:New Underwood 230-kV bus Scenario 5: Mission 115-kV bus (Without extensive upgrades, this site will not accommodate 500 MW; lower MW may be used) Scenario 6:Ft. Thompson 230-kV bus Scenario 7:White 345-kV bus Scenario 8:50 MW at each of the 4 previous sites in scenarios 1 through 7 and 100 MW at 3 sites

24 Study Results – Task 3 Site Impact Studies - Task 1 did not consider outages - Task 3 and 4 results needed for Task 2 evaluation Started with 500 MW at each site In Task 3 for extreme overload and voltage problems reduced power to: MW MW MW - 50 MW Mission was only site limited250 MW

25 Study Results – Task 4 Local Stability Analysis There were no stability problems for local faults at any of Sites 1-7

26 Study Results – Task 4 Task 4 – Transfer Impact Summer Off-Peak Single Contingency Cases - Additional overloads with high hydro - Minnesota Valley-Granite Falls overloads to about 115% in all cases - Site 1: Garrison-Leland 230-kV overloads to 104% and Garrison-Bismarck to 102% - Site 3: Groton 345/230-kV transformer overloads to 107.5% - Site 4: Sidney transformer overloads to 110% - Site 5: Overloads on local 115-kV lines increased to 133% - Site 7: White Transformer overloads to 110% and Watertown transformer to 127%

27 Study Results – Task 4 Overall Results with no System Enhancements Garrison 230 kV250 MW Pickert 230 kV500 MW Ellendale 345 kV250 MW New Underwood 230 kV 50 MW Note 1 & 2 Mission 115 kV150 MW Note 1& 2 Ft. Thompson 345 kV 50 MW Note 2 White 345 kV250 MW Note 1& 2 Case 8Failed Note 1 There were some dynamic voltage violations in the case. Note 2 When NDEX was reduced to 1450 MW for the Ft. Thompson site (similar to the adjustment for North Dakota sites), it was stable for 500 MW of wind generation without other system violations. This is also true for the White site. Reducing NDEX should also increase stability at New Underwood and Mission but they also have other limitations.

28 Study Results – Task 4 Overall Results with System Enhancements Garrison 230-kV500 MW with 35% SC & SVCs Ellendale 345-kV500 MW with 35% SC & SVCs New Underwood 230-kV150 MW with 35% SC Mission 115-kV250 MW with 35% SC Ft. Thompson 345-kV250 MW with 50% SC White 345-kV500 MW with 50% SC Case 8500 MW with 35% SC

29 Summary Task 1 indicates non-firm transmission is available at most of the sites most of the time Task 2 provides an overview of new technologies that can be used to solve some of the limitations Tasks 3 and 4 show limits to the non-firm available capacity that must be solved with system additions such as series compensation Series compensation has other side effects that were not considered in this study

30 Future Work Potential next steps: additional analysis using GridView specific projects such as Tribal wind development for additional study Possible programmatic EIS for Interconnections to Westerns system

31 For Additional Information: Sam Miller Dakotas Wind Study Project Manager Box Billings, MT Ed Weber Transmission System Planning Manager Box Billings, MT Western Area Power Administration Website for the Dakotas Wind Transmission Study Project: