The Public Service Commission of Wisconsin on July 7 issued an environmental assessment on American Transmission Co. LLC‘s (ATC) proposal to improve the existing M-13 single-circuit 115-kV transmission line, between the Kelly Substation in Marathon County, the Bunker Hill Substation in Lincoln County, and the Blackbrook Substation in Langlade County, under what is known as the Line M-13 Reinforcement Project.
With this project, ATC proposes to: build a new 115-kV substation (Ackley Substation) located between the Bunker Hill and Blackbrook Substations; rebuild Line M-13 as double-circuit 115 kV between the Bunker Hill and Blackbrook Substations; retire and remove the Bunker Hill and Blackbrook substations; and uprate Line M-13 from the Bunker Hill Substation to the Kelly Substation. ATC says the project is needed to alleviate potential single contingency overloads on Line M-13, replace aging infrastructure on Line M-13, and improve transmission system protection.
Line M-13 potentially overloads under single contingencies when certain other transmission lines are taken out of service for maintenance. Power flow analysis shows the Bunker Hill-Blackbrook section and Kelly-Bunker Hill section of Line M-13 exceeds its Summer Emergency (SE) rating in the 2024 off-peak expected model under certain contingencies when other lines are under maintenance.
ATC also has asset renewal requirements within the planning study area in the next five to ten years—the replacement of old wood poles and equipment at the Blackbrook and Bunker Hill dubstations. In addition, ATC has protection and operational issues within the planning study area that drive the need for the proposed project.
The project is located in central Wisconsin. It begins at the Kelly Substation in the village of Weston in Marathon County and runs north to the Bunker Hill Substation in the town of Pine River in Lincoln County, and continues east until it terminates at the Blackbrook Substation in the town of Ackley in Langlade County.
- About 8.2 miles of Line M-13 would be rebuilt as a double-circuit line adjacent to the existing line between the Bunker Hill and Blackbrook substations. The old line would be retired and removed.
- About 19 miles of Line M-13 would be uprated, by replacing some existing structures with taller structures to achieve a higher SE rating, between the Kelly and Bunker Hill Substations.
- The new double-circuit line would connect to the new Ackley Substation and existing lines at the existing Bunker Hill and Blackbrook sites.
- The Bunker Hill and Blackbrook Substations would be demolished and removed.
- A new 115 kV four-position ring bus substation (Ackley) would be built on approximately four acres of land. ATC would buy approximately 6.0 acres of land from two landowners in the town of Pine River to support this project and build the new Ackley Substation.
- Remote end work (e.g. relay upgrades) would be performed at the Pine, Kelly, Gardner Park, and Aurora substations located in Merrill, Weston, Mosinee, and Antigo, respectively, to support the new circuits.
ATC estimates the cost of the proposed project to be $29.72m. Of that total, $21.28m would be for transmission line work, $7.46m for substation work, and $980,000 for precertification costs.
ATC evaluated two no-build options, which are do nothing, and retire the M-13 transmission line. ATC found these options would not allow it to reliably meet the electricity needs of its customers. ATC also found that energy efficiency, load management, and other non-transmission options could not cost-effectively provide the required capacity to address the overloads in the project area. Further, ATC determined that renewable resources, both non-combustible and combustible, could not cost-effectively meet the project need. ATC believes that an adequate new natural gas, oil, or coal generation option would provide comparable operational and reliability benefits. However, new generation would cost more than the proposed project.