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Studies and Reports > 2009 MN Biennial Report > WC Planning Zone > Needs: 6.4.10 Morris – Grant County 115 kV Line

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Transmission Projects Report 2009
Section 6.4: West Central Zone
p. 160

6.4.10 Morris – Grant County 115 kV Line

Tracking Number. 2007-WC-N3

Utilities. Otter Tail Power Company and Missouri River Energy Services

Inadequacy. The Morris – Grant County 115 kV line has been shown as an impacted facility during the Big Stone II delivery studies and upgrades will be required in order to provide firm transmission service for the Big Stone II project.

A map of the area is shown on the following page.

Alternatives. In order to increase the capacity of this existing transmission line, it is possible to either reconductor the existing line (replace conductor and use existing structures) or rebuild the existing line (replace conductor and the existing structures).

Analysis. Missouri River Energy Services (MRES) and Otter Tail Power Company (OTP) jointly own the Morris – Grant County 115 kV line. The line is approximately 27 miles in length and has a present summer continuous line rating of 96 MVA, which is thermally limited by its 266 ACSR conductor.

Contingency analysis performed as part of the Big Stone II delivery studies demonstrated that a minimum summer rating of 156 MVA and a winter rating of 175 MVA will be necessary to deliver the Big Stone II generation to the respective participants during seasonal peak conditions.

This line was originally constructed in 1952 of western red cedar poles and H-frame construction. Although this particular line has a history of very reliable service, the age and physical condition of the poles alone eliminate the possibility of replacing only the line’s conductor (i.e. reconductoring). Therefore, significant upgrade of this facility is needed and a complete facility rebuild is the most practical alternative to achieving the required capacity increase. Although detailed engineering has not been completed yet for the rebuild, a conductor size of 795 ACSR provides the required capacity with a reasonable amount of additional capacity margin for future load growth.

Schedule. The line upgrade will be necessary prior to the in-service date of the Big Stone II project. A Certificate of Need is not required to reconstruct the line since it is proposed to remain at 115 kV operation. A Route Permit may be required, depending on whether any changes in the route or the capacity of the conductor are required. This project will have to be undertaken when construction of the Big Stone lines commences (Tracking Number 2005-WCN1).


Transmission Projects Report 2009
Section 6.4: West Central Zone
p. 161

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