Studies and Reports > 2009 MN Biennial Report > NE Planning Zone > Needs: 6.3.2 Cromwell-Wrenshall-Mahtowa-Floodwood Area

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6.3.2 Cromwell-Wrenshall-Mahtowa-Floodwood Area

Tracking Number: 2003-NE-N2

Utility. Minnesota Power and Great River Energy

Inadequacy. The MP and GRE customers in the Cromwell-Wrenshall-Mahtowa areas are supplied by a 90-mile 115 kV line running between 115 kV sources located at the Riverton Substation near Brainerd and the Thomson Substation located south of Duluth. Due to the distances between the two 115 kV sources and the total load served, the voltage in the Mahtowa and Wrenshall areas is approaching unacceptable levels with a loss of the Thomson source. This pending inadequacy was recognized in the 2007 MAPP 10 year reliability assessment.

The Floodwood Area consists of the load served between the Cromwell and Four Corners 115/69 kV sources. GRE serves loads in the Floodwood area via a 69 kV system between Cromwell, Gowan, and Four Corners while MP serves load in the area via a 115 kV radial line sourced from the Blackberry-Cloquet 115 kV line. GRE expects voltage issues for its loads by the 2011 timeframe if either the Cromwell or the Four Corners 69 kV source is out of service. Furthermore, industrial load in the Floodwood area is forecast to increase in the 2014-2015 timeframe. The existing MP radial 115 kV source to Floodwood is not expected to be adequate to reliably serve this expected increase in electric demand.

Tracking Number 2003-NE-N8 (Floodwood Area) has been combined with this Tracking Number and 2003-NE-N8 has been eliminated.

A map of the area is shown following the discussion.

Alternatives. MP and GRE are working together to address both the short term and long term inadequacies in theses two areas.

Near term, the Gowan area is in need of a new source as this area has capacitors at almost every substation served from this system. As recommended by the 2008 GRE Long Range Plan, a new Savanna (Floodwood) 115/69 kV substation will be established in 2011 which will provide a third source into the Gowan area system. This project will address the near term needs in the Floodwood area.

Three alternatives have been identified to address the two area’s long term needs; (1) upgrade of existing lower voltage lines, (2) construction of a new 115 kV line, and (3) distributed generation. Studies to determine which alternative is the best long term solution are ongoing. One alternative being considered is upgrading an existing GRE 69 kV line that runs between Cromwell and Floodwood as a double circuit 115/69 kV line. This alternative would likely address both the MP need in the Cromwell – Wrenshall – Mahtowa area and the MP and GRE Floodwood area need. Other transmission alternatives include new transmission lines between Cloquet and Mahtowa, Floodwood and Mahtowa or a Floodwood-Cloquet-Mahtowa line.

Analysis. A solution that solves both inadequacies (the Cromwell-Wrenshall-Mahtowa areas and the Floodwood area) with one line would potentially have less environmental and social impacts, depending on where it is located, than two separate solutions. Making use of existing corridors and double-circuiting where practical with existing lines would also reduce environmental and social impacts.

Distributed generation has not been eliminated as an alternative; however, operational issues associated with distributed generation and cost of fuel will likely result in a generation alternative having both a reliability and economic disadvantage over a transmission solution. At this time, it appears that a new 115 kV line would provide the best long term solution both electrically and economically. However, no alternatives have been ruled out.

Schedule. GRE has placed an option on land for the Savanna Substation. Substation engineering activities and right-of-way acquisition have started. The projected energization date is Fall 2011.

Because of the desire to find a solution that addresses both problem areas, and because the long term need is not critical at the moment, the schedule for a longer term solution has been extended from what was predicted in the 2007 Report. The utilities will continue to monitor the situation and evaluate options, but the present expectation is that a Certificate of Need application may be filed as soon as 2010 or as late as 2012.

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