Refer to Table ZS-3 and Figure ZS-19

Summary of key findings

• Heavy load growth in Waukesha, Washington, Dodge and Jefferson counties will require voltage and load support. A new 345-kV line from Rockdale to Mill Road (formerly Lannon Junction) is one option being considered to solve these problems.
• Voltage and thermal issues remain in Zone 5 under contingency conditions.
• Thermal, voltage, and load serving issues in Kenosha and Walworth might be resolved with a 138-kV line between Spring Valley and North Lake Geneva

Fifteen 138-kV buses in Waukesha and Washington County experience low bus voltage under NERC Category A or TPL-001-0 conditions (intact system) in 2018.  The fifteen buses are Allerton (93.9%), Bark River (93.7%), Cooney (92.8%), Brookdale East (94.6%), Edgewood (94.5%), Chinook (94.4%), Cooney (93.8%), Cottonwood (92.9%), Germantown (94.4%), Hartford (94.7%), Merrill Hills (94.0%), Mukwonago (94.3%), Maple (94.6%), Summit (93.6%), and Country Aire (94.4%).  In addition, another fourteen 138-kV buses have marginal bus voltages between 95-96%.  It should be pointed out that provisional capacitor banks scheduled for Bluemound in 2010 as well as Mukwonago in 2014 were not modeled in service in the 2018 base case.  In addition, only two Concord generators and one Germantown generator are online at time of peak.  Modeling the Bluemound and Mukwonago capacitors in service as well as running additional generation at Concord and Germantown would improve the voltage in Waukesha and Washington counties.      

Following are the results of the 2018 contingency analysis (NERC Category B or TPL-002-0 conditions) performed on zone 5.    

The Oak Creek–Pennsylvania 138-kV line will load to 100.7% of its summer normal rating under intact system conditions.  Under a number of contingencies, the line can exceed it summer emergency rating by up to 2.3%.  The line conductor is the limiting element.

Splitting the Pleasant Prairie 345-kV bus between bus sections 3 and 4 will cause the Bain transformer #5 to exceed its summer emergency rating by 59.7%.  Bus outages are low probability events.  Relief can be provided by reducing the output of Pleasant Prairie generator #2 to about 350 MW.

The Bain 345/138-kV transformer #4 will exceed its summer emergency rating by 3.7% for an outage of Bain transformer #5.  Reducing Pleasant Prairie generation will provide loading relief.

An outage of the Bain–Albers 138-kV line will result in the Bain–Kenosha 138-kV line loading to 98.7% of its summer emergency rating. 

An outage of either one of the Arcadian–Waukesha 138-kV lines (KK9962 or KK9942) will result in the other Arcadian–Waukesha 138-kV line loading to 100% of its summer emergency rating. The limiting element is the line conductor with clearances set for operation at 200 degrees. The line conductor clearances will be increased in 2010 to permit higher flows under contingency conditions.

An outage of the Bark River–Cottonwood 138-kV line or Bark River–Sussex 138-kV line will cause bus voltages at Cottonwood to drop to 89.0%.  Increasing the amount of Concord generation online will improve voltages in the area.

An outage of the Bark River–Sussex 138-kV line will cause bus voltages at Bark River to drop to 89.5%.  Increasing the amount of Concord generation online will improve area bus voltages.

An outage of the Maple–Saukville 138-kV line will cause bus voltages at Germantown (89.3%), Maple (88.9%) and Country Aire (89.3%) to drop below 900=.0%.  Dispatching Germantown generation will improve bus voltages.

An outage of the Bain–Kenosha 138-kV line will cause the Bain–Albers 138-kV line to load to 121.3% of its summer emergency rating.  The line conductor clearance is the limiting element. 

An outage of Oak Creek 345/138-kV transformer #1 will cause Oak Creek 345/138-kV transformer #2 to load to 99% of its summer emergency rating.

An outage of the Oak Creek–Pennsylvania 138-kV line will cause the Branch–Kansas 138-kV line (108.2%), Nicholson–Ramsey 138-kV line (96.3%), and Oak Creek–Ramsey 138-kV line (96.1%) to approach or exceed their summer emergency ratings.  Increasing line conductor clearances on the Branch–Kansas 138-kV line will provide relief. 

An outage of the Arcadian 345/138-kV transformer #1 causes the Arcadian transformer #3 to load to 120.1% of its summer emergency rating and Arcadian transformer #2 to load to 101.0% of its summer emergency rating.

Splitting the Burlington 138-kV bus will result in low 138-kV bus voltages at Tichigan (87.7%) and Burlington (88.6%).

Past studies have shown low bus voltages in eastern Jefferson, western Waukesha, and southern Washington counties, all areas where load growth has been and is expected to remain high. To provide relief, a new 345-kV line connecting the Madison area with the Milwaukee area is being considered. The components of the project could include:

• Construct a new 345/138-kV Mill Road Substation (formerly known as Lannon Junction) at the intersection of the Cypress-Arcadian 345-kV line, the Arcadian-Granville 345-kV line, Germantown-Bark River 138-kV line and Sussex-Tamarack 138-kV line. This project will improve the 138-kV voltage profile in the area and facilitate expansion of the 345-kV network to the west of this substation. A 500 MVA, 345/138-kV transformer will be installed.
• Construct a Rockdale-Concord 345-kV line adjacent to the existing Rockdale-Jefferson-Concord 138-kV line on existing double-width right-of-way and install a 500 MVA, 345/138-kV transformer at Concord.
• Convert the Bark River-Mill Road 138-kV line (currently built to 345-kV standards) to 345-kV operation and install a 500 MVA, 345/138-kV transformer at Bark River.
• Construct a new 345-kV line from Concord to Bark River.

In addition to improving the voltage profiles in Jefferson, Waukesha and Washington counties, reducing loadings on parallel 138-kV circuits and reducing system losses, the above reinforcements will improve ATC’s existing east-west transfer capability in this region.  Such a project is not being proposed in this Assessment, but may be justified in future Assessments for analysis beyond the current 10-year horizon. Potential economic benefits will need to be reviewed as the future develops.

Provisional projects to install 2-32 MVAR of capacitance at the Mukwonago Substation and uprating the Oak Creek-Pennsylvania 138-kV line are being considered in the 2014 timeframe in order to address remaining voltage and thermal issues.