South Central/Southwest Wisconsin and North Central Illinois
Zone 3

Transmission system limitations in Zone 3

In our analysis of Zone 3, we identified transmission facility overloads between Portage and Columbia substations. These overloads are the result of load modifications in the Portage area.

In addition, other emerging issues resulting in potential facility overloads could include steady growth in certain areas and different generation dispatches. The most severe limitations are expected to 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 0.6 percent annually between now and 2028, and employment is projected to grow about 1.1  percent each year for the same time period. Dane County is projected to realize the largest total increase in population and employment. Dane County is also projected to have the highest annual growth rates in population and employment at 0.9% and 1.4%, respectively.

Electricity usage growing

Electric load is forecasted to grow approximately 0.7% annually through 2029 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 DescriptionProject #In-service yearNeed driver
Boscobel–Lone Rock 69-kV (Y-124), rebuild12019Condition and performance
Spring Valley–North Lake Geneva 138‑kV line22019T‑D interconnection and reliability
Portage–Staff–North Randolph 138-kV lines (X-6) (X-98), rebuild32020Condition and performance
Sheepskin–Stoughton 69-kV (Y-12), rebuild42021Condition and performance
Cardinal SS–Hickory Creek SS 345-kV, line construction52023Reliability, economic and policy

Zone 3 Proposed Projects

Project DescriptionProject #In-service yearNeed driver
J870/J871 GIC Highland, generator interconnection facilities and network upgrades62020G‑T interconnection
J584 GIC Jordan SS, generator interconnection facilities and network upgrades information72021G‑T interconnection
Northern Lights Substation, new T-D interconnection82021T‑D interconnection
Portage SS–Columbia SS 138-kV (X-13/X-20), rebuild existing double circuit92024Reliability
Hillman–Darlington 138-kV line (X-14/X-101), rebuild102026Condition and performance

Zone 3 Provisional Projects

Project DescriptionProject #In-service yearNeed driver