NEWS FROM WESTERN AREA POWER ADMINISTRATION

FOR IMMEDIATE RELEASE: Feb. 24, 2006
Contact: LaVerne Kyriss, (720) 962-7051, kyriss@wapa.gov

DAKOTAS WIND STUDY RESULTS SHOW PROMISE

BILLINGS, Mont. —Interest in wind generation is increasing throughout Western’s service territory, and new insight gained from Western’s recently completed Dakotas Wind Transmission Study will identify improvements to the grid to help deliver renewable resources to consumers.

Congress appropriated $750,000 in non-reimbursable funds for Western to perform the two-year study to examine the local effects of adding 500 MW of new wind generation to the Dakotas’ current transmission system. Final results of the study were released in December 2005.

“The results will help developers make business decisions involving wind development in the Dakotas, said Sam Miller, project manager for the Dakotas Wind Transmission Study. “As renewable resources such as wind continue to grow in importance in Western’s service territory, one imperative is to ensure improvements to the grid keep pace.”

Study involved four tasks

The study scope of work included four tasks: analyzing nonfirm transmission, assessing transmission technology relative to new wind generation, examining how new wind generation would interconnect to the existing transmission systems and analyzing how it would be delivered into the market. Western chose seven separate interconnection sites in North Dakota and South Dakota for the study based on public comments, wind resource maps, the Western Interconnection transmission queue, tribal projects and wind developer projects.

Final study results showed that for the seven wind sites studied, non-firm transmission is available most of the time across three monitored areas for up to 500 MW of new wind generation under normal system intact conditions. However, some of the sites are limited to less than 500 MW without additional system enhancements. The study indicated that some overloads and dynamic stability problems resulted when wind generation was added, but dynamic line rating and reconductoring could mitigate those problems without adding new transmission lines to the system.

“It was interesting to learn that non-firm transmission was available most of the time and should not be a constraint to hold back wind development,” Miller said about the final results.

Study finds non-firm transmission capacity available

Task 1 examined how much transmission is contracted and how much transmission is actually scheduled hourly, daily and seasonally across three key corridors:

• 18 transmission lines in North and South Dakota and Minnesota, in the North Dakota Export Boundary
• Watertown-to-Granite Falls 230-kV transmission line
• Eight transmission lines east and southeast of Fort Thompson and west and northwest of Fort Randall, S.D.

Task 1 results indicated that non-firm transmission capacity was available across the critical interfaces to transfer almost all of the wind energy for the 500 MW installed at any one of the seven sites.

Task 3 determined the local system requirements to connect proposed wind generation to the existing system and identified any local enhancements needed to accommodate new generation. The seven wind generation zones evaluated for interconnection were: Garrison, N.D.; Wishek/Ellendale/Edgeley, N.D.; Pickert, N.D.; Rapid City, S.D.; Mission, S.D.; Fort Thompson, S.D.; Summit/Watertown/Toronto/ White/Brookings/Flandreau, S.D.

Task 4 analyzed the firm transfer capability to ship power from wind sites to markets. Also analyzed were regional stability performance and limitations and the potential for some transmission technologies to increase power transfers from the Dakotas.

Technology improvements could mitigate problems  

Since Tasks 3 and 4 indicated some steady-state and dynamic stability problems when wind generation was added, Task 2 provided an overview of some transmission technologies to mitigate overloads and stability problems without adding new transmission lines. To solve some of these issues, Task 2 considered the following technologies:

• Static var compensation to improve transmission system performance by providing reactive power to control dynamic voltage swings
• Series compensation to improve stability
• Phase-shifting transformers to improve stability and thermal loading by assisting with power flow control
• Dynamic line ratings to increase transfer capacity by calculating the transmission line’s real-time, dynamic thermal rating based on real-time monitoring of lines and weather conditions
• Reconductoring to increase transfer capacity by replacing transmission line conductors with newer composite materials that can carry more current at the same or higher voltage. This evaluation included an assessment of impacts on existing tower structures and rights-of-way.

Task 2 showed that for overloading problems, dynamic transmission line rating and reconductoring the lines can mitigate problems. For dynamic instability and low voltage problems, series capacitors and static var compensation or static synchronous compensators can improve system performance.

Final study results will be vital to renewable resource developers who are increasingly requesting interconnections and transmission service on Western’s high-voltage lines.

“The wind industry, rural Dakotas and transmission ratepayers will all benefit from the study results,” Miller concluded.

Study information is available online at http://www.wapa.gov/ugp/study/DakotasWind/Default.htm.

Western Area Power Administration annually markets and transmits more than 10,000 megawatts of power from hydroelectric powerplants owned and operated by the Bureau of Reclamation and the U.S. Army Corps of Engineers in 15 western and central states.  It is part of the Department of Energy.

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