South Central/Southwest Wisconsin and North Central Illinois
Zone 3

Transmission system characteristics in Zone 3

ATC delivers power in Zone 3 with various transmission facilities including:

  • Columbia-North Madison 345-kV lines,
  • Columbia-Rockdale 345-kV line,
  • Paddock-Rockdale 345-kV line,
  • Paddock-Wempletown 345-kV line,
  • Rockdale-Wempletown 345-kV line, and
  • 138-kV facilities from the Nelson Dewey Power Plant, around the Madison area, and in the northwest and southeast portions of Zone 3.

Transmission system performance issues in Zone 3 include voltage instability, limited import capability, overloaded lines and equipment and low system voltages. The causes of these emerging issues include steady growth in certain areas, new power plants and different
generation dispatch scenarios.

Transmission system limitations in Zone 3

In our analysis of Zone 3, we identified low voltages, high voltages and transmission-facility overloads. Low voltages are located in the Verona, Beloit, Hustisford and Waunakee areas. Several overloads on 138‑kV and 69‑kV facilities in Zone 3 are emerging concerns.

Electric System Overview

Increases expected in population, employment – Population in Zone 3 is projected to grow about 0.9 percent annually between now and 2021, and employment is projected to grow about 1.3 percent each year for the same time period. Dane County is projected to realize the largest increase in population, and Sauk County is projected to have the largest increase in employment.

Electricity usage growing – Electric load is expected to grow approximately 1.38 percent annually through 2021 for all of Zone 3.

Transmission Projects in Zone 3

We have implemented two network projects in Zone 3 since the 2011 Assessment, most notably the Brodhead to South Monroe 69‑kV line rebuild project.

Our current plans in Zone 3 include 49 system reliability and economic projects between 2012 and 2026, 15 of which are driven by our new Study-Based Rating Methodology. These projects are in various stages of development. The most notable planned, proposed, provisional and asset renewal projects in Zone 3, along with their projected year of completion and the factors driving the need for the projects, are listed below.

Zone 3 includes the counties of:
  • Columbia , WI
  • Crawford (S) , WI
  • Dane , WI
  • Dodge , WI
  • Grant , WI
  • Green , WI
  • Iowa , WI
  • Jefferson , WI
  • Lafayette , WI
  • Richland , WI
  • Rock , WI
  • Sauk , WI
  • Walsworth , WI
  • Winnebago (N) , IL

Zone 3 Planned Projects

Project DescriptionIn-service yearNeed driver
Rockdale-Cardinal 345‑kV line2013Overloads and low voltages, improve transfer capability to Madison area, avert voltage collapse, lower system losses

Zone 3 Proposed Projects

Project DescriptionIn-service yearNeed driver
Sun Valley Tap-Oregon 69‑kV line rebuild2016Overloads and improve line condition and area voltages
Badger Coulee: La Crosse area-North Madison-Cardinal2018Reliability, economics and public policy
Spring Valley-North Lake Geneva
138‑kV line construction
2019Overloads and low voltages, provide network service
Cardinal Bluffs: Dubuque County area-Cardinal
345-kV line construction
2019Reliability, economics and public policy

Zone 3 Provisional Projects

Project DescriptionIn-service yearNeed driver
Colley Road-Brick Church 69‑kV line rebuild2018Overloads and low voltages
Gran Grae-Boscobel 69‑kV line rebuild2019Overloads
Lake Delton-Birchwood 138‑kV line construction2020Overloads and low voltages
Cardinal-Blount 138‑kV line construction2020Overloads and low voltages
Hubbard-East Beaver Dam 138‑kV line construction2022Overloads and low voltages
West Middleton-Pheasant Branch 69‑kV line rebuild2022Overloads and low voltages

Zone 3 Asset Renewal Projects

Project DescriptionIn-service yearNeed driver
Doylestown-Rio Pumping Station 69‑kV line rebuild2013Condition and performance
Dam Heights-Portage 69‑kV line rebuild2016Condition and performance
Darlington-Hillman 138‑kV line rebuild2016Condition and performance
Concord-Rubicon-Butler Ridge-Hartford
138‑kV line rebuild
2016Condition and performance
Belmont-Rewey 69‑kV line rebuild2018Condition and performance
Boscobel-Lone Rock 69‑kV line rebuild2018Condition and performance
West Middleton-Stagecoach 69‑kV underground
cable replacement
2019Condition and performance