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Studies and Reports > 2009 MN Biennial Report > NE Planning Zone > Needs: 6.3.6 Taconite Harbor-Grand Marais Area

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Transmission Projects Report 2009
Section 6.3: Northeast Zone
p. 96

6.3.6 Taconite Harbor-Grand Marais Area

Tracking Number. 2003-NE-N6

Utility. Great River Energy and Southern Minnesota Municipal Power Agency

Inadequacy. The concern here is system intact low voltage on a fifty mile long 69 kV line that runs along the North Shore. The load served by this line has been growing at a rate of approximately 6% per year and includes both GRE and SMMPA load. The voltage will be below acceptable levels without an upgrade sometime between 2011 and 2015.

Alternatives. The utilities identified several alternatives in the 2003 Report, including construction of a new 115 kV line, rebuild and upgrade of the existing 69 kV line, installation of capacitors, and installation of additional generation.

Analysis. GRE completed the installation of the Arrowhead generation station in Fall 2008 at the Colvill substation. Nine, two megawatt diesel generators were installed as an emergency source if the transmission feed from Taconite Harbor should be lost. GRE also installed two 3.5 MVAR capacitor banks at the Maple Hill substation in 2008 to help boost transmission voltages during on-peak situations.

With these capacitor and generation additions in place, GRE will pursue transmission line rebuilds to address area thermal loading and voltage concerns. Line rebuilds are warranted as the area loading is approaching the limits of the existing transmission capacity with much of the existing transmission circuit being 1950’s vintage and nearing the end of its useful life. Any rebuild would be constructed to 115 kV design standards for future conversion.

Schedule. GRE will monitor the area load growth to determine when the line rebuilds need to take place. It is anticipated that no action would be required until at least 2011.


Transmission Projects Report 2009
Section 6.3: Northeast Zone
p. 97

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