The 345-kV line would be built between Xcel Energy‘s existing Wilmarth substation, located on the north side of the City of Mankato, Minnesota, and ITC Midwest’s Huntley substation, located south of Winnebago, Minnesota, the companies said.
The application is one of two applications submitted to the commission for the project, the companies said, adding that the other application is a certificate of need application that was submitted on Jan. 17 in Docket No. E002, ET6675/CN-17-184.
As part of the certificate of need process, the commission will determine whether the project is needed, while the route permit process will focus on where the transmission line should be located, the companies said.
As noted in the Jan. 17 certificate of need application, the project consists of the approximately 50-mile line, and the necessary modifications to the existing Wilmarth and Huntley substations to accommodate the new line. Route alternatives for the proposed line traverse Blue Earth, Faribault, Martin, and Nicollet counties in Minnesota.
The companies added that the project was studied, reviewed, and approved by the Midcontinent ISO (MISO) Board of Directors as a market efficiency project (MEP) in December 2016, as part of its annual Transmission Expansion Plan (MTEP16) report.
“As early as 2008, transmission planners documented congestion on the transmission system along the Minnesota/Iowa border,” the companies said. “Since that time, despite other transmission line additions, congestion in this area has progressively worsened. Accordingly, MISO turned its attention to this area of the transmission system and, ultimately, the MISO Board of Directors studied, reviewed, and approved the project as an MEP.”
As an MEP, the project would help relieve the current transmission congestion in the Minnesota/Iowa border area, which would improve the efficiency of MISO’s energy market resulting in lower wholesale energy costs, the companies said.
The project would also improve the deliverability of wind generation as it would reduce curtailments, allowing the maximum amount of that renewable generation to meet customer demands, the companies said. Reducing curtailments improves energy delivery, reduces system generation costs, and provides environmental benefits in the form of lower carbon emissions, the companies added.
Furthermore, the project would improve the robustness of the regional backbone transmission system by improving the efficient delivery of energy and enabling the system to better withstand contingencies under multiple future scenarios, the companies said.
The companies noted that they would own the line jointly as tenants in common, adding that the equipment and improvements inside the Wilmarth substation would be owned by solely by Xcel Energy, while the equipment and improvements inside the Huntley substation would be owned solely by ITC Midwest. As the project manager, Xcel Energy would be responsible for the construction and maintenance of the proposed line, with each party to be responsible for the construction and maintenance of its substation, the companies said.
In evaluating the economic benefits of the project, the key indicator is its benefit-to-cost ratio, the companies said, adding that that ratio is dependent on the total cost of the project compared to the total adjusted production cost (APC) savings that the project would provide over time. Accordingly, cost will be an important consideration in selecting the route and design for the project.
The companies added that given the project’s unique nature, they are proposing four route alternatives – the Purple Route, Green Route, Red Route, and Blue Route – and several design options that result in nine distinct route/design combinations. Those route/design options have total costs ranging from $105.8m to $138m (2016 dollars), the companies said.
The line would be built of steel pole structures in either single – monopole – or two-pole H-frame configuration, except in certain locations where multiple pole or other specialty structures may be required, the companies said.
Further discussing the routes, the companies noted that the Purple Route is the westernmost route that they are proposing for the project and is about 52 miles long. The Green Route is about 45 miles long and follows a relatively direct path to the Huntley substation, generally following property lines through farmland and an existing transmission line. The Red Route, the companies added, is about 46.5 miles long and shares the same route as the Green Route for its northernmost 12.5 miles. The Blue Route is about 57 miles long and is the easternmost route, the companies said.
For the Purple Route, the companies propose three different design options: a single-circuit H-frame; a single-circuit monopole; and a double-circuit monopole. The companies also said that for the Green Route, they are proposing two design options: single-circuit H-frame structures, or single-circuit monopole structures.
For the Red Route, the companies said that they are proposing to double circuit the line in all areas where these routes follow existing transmission line corridors, and in the areas where they do not follow such corridors, the companies propose either single-circuit H-frame structures, or single-circuit monopole structures. For the Blue Route, the companies said that they propose two different design options: a single-circuit H-frame, and a single-circuit monopole.
Among other things, the companies said that construction of the project, if approved, is anticipated to begin in 2020, and the project is expected to be in service by the end of 2021.