Transmission system characteristics in Zone 5

ATC delivers power in Zone 5 with various transmission facilities including:

• The southern portion of 345‑kV lines from Point Beach and Edgewater,
• The Saukville, Arcadian, Granville, Oak Creek and Racine 345/138‑kV substations,
• The transmission lines emanating from the Pleasant Prairie and Oak Creek power plants,
• 230‑kV facilities near Milwaukee, and
• A significant 138‑kV network in the Milwaukee area, a portion of which is underground.

Apart from the analysis performed in this Assessment, there is one major area event that could impact transmission plans in Zone 5. The proposed road rebuild of the Zoo interchange is moving forward with the following in-service dates:

• Expand/update Watertown Plank area (2013),
• Expand/update Highway 100/Highway 45 area (2014), and
• Expand/update remainder of freeway (2015-2018).

The road relocation project results in new projects to reconfigure the transmission system around Brookdale, Bluemound and 96th Street substations, as well as the construction of an 8-position ring bus at 96th Street.

Transmission system limitations in Zone 5

Key system performance issues in Zone 5 include:

• Heavy flows on aging facilities,
• Heavy flows from the west (Zone 3) resulting in heavily loaded 138‑kV facilities in the western portion of Zone 5,
• Heavy market flows from and to the south, resulting in high 345‑kV and 138‑kV line loadings and the need to monitor potential multiple contingency conditions, and
• Sagging voltage profile in portions of Washington and Waukesha counties.

Load growth in Waukesha and Washington counties is projected to exceed the capabilities of the existing 138 kV system in those areas, signaling the need for future transmission system reinforcements. 

Electric system overview

Increases expected in population, employment – Population in Zone 5 is projected to grow 0.6 percent annually between now and 2022, and employment is projected to grow 1.0 percent in the same time period. Waukesha County is projected to realize the largest increase in both population and employment.

Electricity usage growing – Peak electric demand typically occurs during the summer months. Large industrial loads in the Milwaukee metropolitan area, including Charter Steel and Miller Brewing, are among the largest electricity users in the zone.

Electric load is projected to grow approximately 1.04 percent annually through 2022.

Transmission projects in Zone 5

Our current plans in Zone 5 include 24 system reliability and economic projects between 2013 and 2027, 17 of which are related to 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 5, along with their projected year of completion and the factors driving the need for the projects, are listed below.