Studies and Reports > 2009 MN Biennial Report > WC Planning Zone > Needs: 6.4.7 Big Stone II Interconnection

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6.4.7 Big Stone II Interconnection

Tracking Number. 2005-WC-N1

Utilities. Missouri River Energy Services, Montana-Dakota Utilities, Heartland Consumers Power District, and Central Minnesota Municipal Power Agency

Inadequacy. A new coal-fired generator is being proposed at the existing Big Stone site in northeastern South Dakota. Interconnection studies performed within MISO have determined that new transmission will be required to allow for interconnection of this project.

A map of the area is shown following this section.

Alternatives. During the MISO interconnection study, two base 230 kV alternatives were evaluated. These were:

Big Stone – Johnson Jct. – Morris 230 kV line with a Big Stone – Canby – Granite Falls 230 kV line.

Big Stone – Willmar 230 kV line with a Big S tone – Canby – Granite Falls 230 kV line.

MISO interconnection studies have determined that the two base alternatives had similar system performance with the new Big Stone generator added to the system.

Selected Alternative. The project participants have chosen to pursue the Morris and Granite Falls transmission combination over the Willmar and Granite Falls combination for several reasons, including cost, less new transmission corridor, and better coordination with CapX 2020. This alternative involves two new transmission lines: (1) a 230 kV line from the existing Big Stone Substation in South Dakota to the Morris Substation in Minnesota, and (2) a line from a new Big Stone Substation to the Canby Substation to the Granite Falls Substation. The line to Morris will replace an existing 115 kV line from Ortonville to Johnson Jct. to Morris and will be constructed in the existing 115 kV line corridor. The line section from Big Stone to Canby will be constructed utilizing a new corridor. The line section from Canby to Granite Falls will replace an existing 115 kV line and will utilize the existing right-of-way.

The Big Stone II transmission plan has been coordinated with other regional transmission efforts by planning to construct the line section from Big Stone to Canby to the new Hazel Creek Substation (approximately 12 miles south of Granite Falls) to 345 kV standards but operated at 230 kV until the proposed CapX SW Minnesota to Twin Cities 345 kV (Brooking –Hampton) line is constructed. The line section from the Hazel Creek substation to Granite Falls will be constructed for and operated at 230 kV. Depending on the timing of these two projects (Big Stone II and CapX Brookings), it is possible that the Granite Falls line could be operated at 345 kV immediately if the Hazel Creek Substation is available through the CapX Brookings project.

Schedule. The Public Utilities Commission issued a Certificate of Need and Route Permits for the Minnesota portion of the two new transmission lines, one from the Big Stone Plant to Morris, Minnesota, and one from the plant to Granite Falls, Minnesota, on March 17, 2009. On September 11,2009, Otter Tail Power Company, which had been a joint applicant in the project, advised the Public Utilities Commission that it was withdrawing from participation in the project. The remaining four utilities are in discussions with potential additional partners in the project and have informed the Commission that they will advise the Commission of their progress by the end of November 2009.

PUC Docket Numbers. CN-05-619 (Certificate of Need) TL-05-1275 (Route Permit)

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