Studies and Reports > 2009 MN Biennial Report > TC Planning Zone > Needs: 6.5.11 Southwest Metro 115 kV Development (Hennepin, Scott and Carver counties)

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6.5.11 Southwest Metro 115 kV Development (Hennepin, Scott and Carver counties)

Tracking Number. 2007-TC-N1

Utility. Great River Energy and Xcel Energy

Inadequacy. The study region has been subdivided into three areas:

Area 1 – between the City of Glencoe and West Waconia. Based on the study results, the City of Glencoe would experience low voltages during the loss of its primary 115 kV source from McLeod. The loss of the 115 kV source from the Carver County Substation also results in a number of thermal and voltage problems in the area. Due to the age of the system in the region, the 69 kV lines in this area have been a source of poor reliability in the past. Due to load growth in this area, the City of Glencoe is planning to build a new distribution substation to the East side of the City.

Area 2 – between West Waconia and Scott County. This area is found to be a high load growth corridor. Minnesota Valley Electric Co-op built the new Victoria distribution in this area to meet the load demand. The proposed Chaska Bio Technology Park could potentially increase the transmission demand in this region.

Area 3 – between Scott County and Westgate. This area is found to experience thermal overloads on the 115 and 69 kV lines between Scott County and Westgate under certain contingencies.

A map showing the area is found following the discussion.

Alternatives. Two transmission alternatives have been studied as a long-term solution to the inadequacies in the region. Both alternatives consist of the construction of several sections of 115 kV lines.

Preferred Plan: The preferred alternative involves three sections of 115 kV lines.

(1)

Build a new 115 kV line from the existing Glencoe 115 kV substation to the proposed new distribution substation east of the City of Glencoe. Rebuild the 69 kV line from Glencoe East to Lester Prairie tap to a 115 kV and 69 kV double circuit. Relocate the distribution load from the Plato Substation to the Glencoe East Substation. Convert the 69 kV line from the Lester Prairie tap to Young America to West Waconia to 115 kV. Extend the 69 kV line from Waconia towards the Carver Co – Augusta 69 kV line with a 3 way tap switch. This option also requires installing a capacitor at the existing Plato Substation.

(2)

Rebuild the 69 kV line from the 3 way tap switch on the Carver Co – Augusta 69 kV line towards Augusta to 115 kV standards with a bigger conductor. Serve Chaska, Augusta and Victoria from the Carver Co Substation by opening the line between Chaska and Scott Co.

(3)

Convert the 69 kV line connecting Scott County, Excelsior, Deephaven, and Westgate to 115 kV.

Alternative Plan: This alternative also involves three sections of 115 kV lines, including the first two described under the Preferred Plan. The third action is different under the Alternative Plan.

(3) Rebuild the existing 115 kV line from Scott County to Minnesota River to Bluff Creek to a higher capacity and upgrade some of the 69 kV facilities between Scott County and Westgate along with the Westgate 115/69 kV transformer.

Distributed Generation. Distributed generation was studied as an alternative to the transmission option. However, due to the cost and size of generators required at various locations to mitigate the violations, it was determined that distributed generation is not a viable solution to problems in the study area.

Analysis. As the study region is close to the Twin Cities Metropolitan Area, the analysis to date has focused on various transmission options to address the situation in this high-growth area. Initial results show that a 115 kV system should be adequate to address the need for more energy. The economic and environmental analysis and impacts of any new transmission lines are yet to be determined. The proposed facilities in the preferred plan are sufficient to meet the load serving needs in the study region in the near term and any future needs can be addressed as incremental upgrades near Chaska and Scott Co as required.

Schedule. Xcel Energy is planning on filing for a Certificate of Need for the 115 kV lines from Glencoe to West Waconia and Scott Co to Westgate in late 2009 or early 2010. The expected in-service date for the projects is between 2012 and 2013.

Click here or on map below to download high resolution PDF map.