Long Range Transmission Plan

The Midcontinent Independent System Operator, in shared responsibility with utilities and states, is leading the Long Range Transmission Planning (LRTP) effort.  

The goal of MISO’s LRTP projects is to ensure reliability while integrating the different operating characteristics of new generation resources and increase the resiliency of the grid in the face of severe weather events.  

The LRTP efforts have been broken into up to four tranches. The first tranche was unanimously approved by the MISO Board of Directors in July 2022. The estimated cost of LRTP Tranche 1 Portfolio is $10.3 billion. 

As part of the Tranche 1 portfolio, ATC is collaborating with Xcel Energy on multiple projects. ATC is taking the lead in building LRTP Tranche 1 Project 6, which we call the Grid Forward – Central Wisconsin Project. This project includes a rebuild of approximately 160 miles of existing power line to add a new, approximately 200-mile, 345,000-volt power line and a substation expansion near Arpin, Wisconsin. ATC filed an application with the Public Service Commission of Wisconsin for the project in July 2024.  

The second phase of the LRTP portfolios, called Tranche 2, is currently underway. We have participated in the identification of potential projects that will reinforce our system to address current and anticipated needs and benefit energy consumers regionally and in our service area. We anticipate MISO’s board of directors will approve the first phase of Tranche 2, known as Tranche 2.1, by the end of 2024. 

The most current information on the Long Range Transmission Plan can be found on MISO’s Long Range Transmission Planning Page. 

Grid Forward – Central Wisconsin Project 

The Grid Forward – Central Wisconsin Project is included in ATC’s portion of the Midcontinent Independent System Operator’s LRTP Tranche 1 portfolio. The project is needed to relieve constraints on the electric grid, improve reliability and provide access to lower-cost energy including renewable generation. ATC and Northern States Power Company, a subsidiary of Xcel Energy, are jointly proposing the project, which crosses 10 counties in central Wisconsin. 

The project includes: 

• Rebuilding about 175 miles of existing power lines to support the construction of a new, approximately 200-mile, 345-kV power line from the Tremval Substation in Trempealeau County to the Arpin Substation in Wood County and from the Arpin Substation to the Columbia Substation in Columbia County. 

A Certificate of Public Convenience and Necessity (CPCN) application was submitted to the Public Service Commission of Wisconsin in July 2024. The in-service date is anticipated to be in 2030.