Dakotas Wind Transmission Study

South Dakota Legislative Briefing

Pierre, South Dakota

January 18, 2006

Edward P. WeberTransmission System Planning ManagerUpper Great Plains Region

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Overview

Study BackgroundStudy ParametersStudy ResultsFuture Work

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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

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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

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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

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Task 1: Analyze Non-FirmTransmission 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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Task 1 Cont’d: 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

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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

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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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Task 4: Study the Delivery to Marketof 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

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Study Results: Task 1

Transmission constraint evaluation- Monitored NDEX limit

- Monitored limit on each line in each interface - NDEX- Ft Thompson- Watertown

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Flow Data from Western

NDEX 2003 HOURLY MEASUREMENTS

-1000

-500

0

500

1000

1500

2000

0 2000 4000 6000 8000 10000

HOURS

MW

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Benchmark NDEX Flow Data from Gridview Simulation

NDEX GRIDVIEW RESULTS FOR 2003

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-500

0

500

1000

1500

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0 2000 4000 6000 8000 10000

HOURS

MW

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Measured NDEX Flows Minus GridView NDEX Flows

2003 NDEX MEASURED MINUS NDEX FROM GRIDVIEW

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-500

0

500

1000

1500

2000

1

2001

4001

6001

8001

HOURS

MW

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Results from Gridview Analysis for 2003 (Low Hydro)For Low Hydro, NDEX was limiting for:1. 14 hours for Garrison site2. 3 hours for Ellendale site3. 9 hours for Pickert siteFt Thompson Interface not limitingWatertown Interface not limiting

For High Hydro, NDEX was limiting for:1. 32 hours for Garrison site2. 2 hours for Ellendale siteFt Thompson Interface not limitingWatertown Interface not limiting

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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

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Study Results – Task 2Transmission 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)

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Study Results – Task 2 Transmission Enhancements For Steady- State

Re-conductor Transmission Lines

ACSR ACSS/TW ACCR Aluminum Area: 795 kcmil 795 kcmil 1020 kcmil Size Same Same Same

Weight Same Slightly higher

Same

Rated Ampacity (amperes): 905 1615 1902 Max Operating temp: 75oC 200oC 200oC High Temp Sag: High Low Very Low Inductive Heating: Standard Low Very Low Line Loss: Standard Low Less Al Conductivity (%IACS): 52% 68% 63% Tensile Strength 31,000 lbs 15,600lbs 41,000 lbs

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Study Results – Task 2Transmission Enhancements Cont’dDynamic Transmission Line RatingsWind generation starts at about 3.5 m/sMax wind generation from 12 m/s to 25 m/sWith max generation at 12 m/s, assume nearby lines have 33% or 4 m/s windWind angle to line is 15 degrees then wind correction factor is 0.534 m/s x 0.53 = 2.12 m/sConvection cooling increases 187% over 0.61 m/s in conductor tablesConvection cooling is > 85% of total cooling so conductor dynamic rating will increase upto 170%

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Study Results – Task 3-4Task 3

- Interconnection studies for each of the seven sites

- Determined local system requirements

Task 4- Analyzed transfer capability - Analyzed regional stability performance

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Study Results – Task 3System 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

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Study Results – Task 3Site 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:

- 375 MW- 250 MW- 150 MW- 50 MW

Mission was only site limited―250 MW

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Study Results – Task 4

Local Stability Analysis

There were no stability problems for local faults at any of Sites 1-7

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Study Results – Task 4Task 4 – Transfer Impact Summer Off-PeakSingle 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%

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Study Results – Task 4Overall Results with no System Enhancements

Garrison 230 kV 250 MW

Pickert 230 kV 500 MWEllendale 345 kV 250 MWNew Underwood 230 kV 50 MW Note 1 & 2Mission 115 kV 150 MW Note 1& 2Ft. Thompson 345 kV 50 MW Note 2White 345 kV 250 MW Note 1& 2Case 8 Failed

  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.

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Study Results – Task 4Overall Results with System Enhancements

Garrison 230-kV 500 MW with 35% SC & SVCsEllendale 345-kV 500 MW with 35% SC & SVCsNew Underwood 230-kV 150 MW with 35% SC Mission 115-kV 250 MW with 35% SC Ft. Thompson 345-kV 250 MW with 50% SC White 345-kV 500 MW with 50% SC Case 8 500 MW with 35% SC

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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

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Future Work

Potential next steps:

additional analysis using GridViewspecific projects such as Tribal wind

development for additional studyPossible programmatic EIS for

Interconnections to Western’s system

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For Additional Information: Sam Miller

Dakotas Wind Study Project ManagerBox 35800Billings, MT 59107-5800406-247-7466

Ed WeberTransmission System Planning ManagerBox 35800Billings, MT 59107-5800406-247-7433

E-mail: UGPDakotasWindTS@wapa.gov

Western Area Power Administration Website for the Dakotas Wind Transmission Study Project: http://www.wapa.gov/ugp/study/DakotasWind/