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
  • Rockdale-Cardinal 345-kV line, and
  • 138‑kV facilities from Nelson Dewey, around the Madison area, and in the northwest and southeast portions of Zone 3.
Transmission system limitations in Zone 3

In our analysis of Zone 3, we identified a number of transmission facility overloads. These overloads are due to new generation in the Janesville and Darlington areas. In addition, other emerging issues resulting in facility overloads include steady growth in certain areas and different generation dispatches. The most severe limitations occur during both peak and off‑peak periods.

Electric system overview

Increases expected in population, employment Population in Zone 3 is projected to grow about 0.8 percent annually between now and 2027, 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 employment. Dane County is also projected to have the highest growth rate in population and employment.

Electricity usage growing

Electric load is forecasted to grow approximately 0.7 percent annually through 2028 in Zone 3.

Transmission projects in Zone 3

The most notable planned, proposed and provisional network projects 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
  • Walworth , WI
  • Winnebago (N) , IL

Zone 3 Planned Projects

Project DescriptionIn-service yearNeed driver
Badger Coulee: Briggs Rd–North Madison–Cardinal 345‑kV line construction 2018Reliability, economics and public policy
J390: Kittyhawk Substation, new G‑T interconnection2019G‑T interconnection
J395: Darlington–North Monroe 138‑kV line (X‑49), Uprate2019G‑T interconnection
Lone Rock–Boscobel 69‑kV line (Y‑124) rebuild2019Condition and performance
Spring Valley–North Lake Geneva 138‑kV line2019Overloads and low voltages, provide network service
Portage–Staff–North Randolph 138‑kV lines (X‑6), (X‑98), rebuild2020Condition and performance
Sheepskin–Stoughton 69‑kV line rebuild2021Condition and performance

Zone 3 Proposed Projects

Project DescriptionIn-service yearNeed driver
Northern Lights Substation, new T‑D interconnection2020T‑D interconnection
Cardinal–Hickory Creek 345‑kV line construction2023Reliability, economics and public policy

Zone 3 Provisional Projects

Project DescriptionIn-service yearNeed driver
Cardinal–Blount 138‑kV line construction2029Overloads and low voltages