Refer to Table ZS-1 and Figure ZS-13

Summary of key findings

• By 2010, construction of a new 345-kV line from Morgan to Werner West will significantly increase transfer capability between Wisconsin and the Upper Peninsula, avert overloads in and around the Green Bay area, improve 138-kV voltage profiles in the Fox Valley and Green Bay areas and significantly lower losses.
• Load growth in Marinette and Menominee areas will drive the need for additional 138/69-kV transformer capacity.
• Load growth and generation patterns in the Upper Peshtigo area will drive the need for transmission reinforcements.

Several potential line overloads were confirmed and new low voltage issues were identified in Zone 4 based on the 2009 model.

As noted in the Northern Umbrella Plan discussion in previous 10-Year Assessments, the most chronic problem plaguing day-to-day operation of ATC’s transmission system is the limited transfer capability during non-peak periods between Wisconsin and Michigan’s Upper Peninsula. The resulting effects include:

• uneconomic dispatch of generation,
• interruption or curtailment of transmission service,
• operating near thermal and voltage limits for extended periods of time and
• limited ability to schedule maintenance without invoking redispatch, system reconfiguration or other measures.

Most of the short-term solutions discussed in earlier 10-Year Assessments are already in service. Those are:

• rebuilding the Morgan-Falls-Pioneer-Stiles 138-kV line (2005),
• rebuilding the Plains-Amberg 138-kV line (2005),
• rebuilding/converting the West Marinette-Amberg 69-kV line to 138 kV (2005),
• rebuilding the Amberg-Crivitz-Stiles 138-kV line (2006),
• constructing a 345/138-kV Substation at Werner West (2006), and
• rebuilding the Hiawatha-Indian Lake 69-kV line (2006).

As discussed in the 2007 10-Year Assessment Update, the following projects have been planned in Zone 4 as long-term solutions to these issues:

• construct a new 345/138-kV substation at Werner West (in service),
• construct a Cranberry-Conover 115-kV line (in service),
• rebuild and convert the Conover-Plains 69-kV line to 138-kV (2010), and
• construct a new Morgan-Werner West 345-kV line (Dec 2009).

The Morgan-Werner West 345-kV line in 2009 will aid the transmission system by reducing the south to north loading on the 138-kV lines through the Green Bay area, thus deferring or eliminating the need for numerous 138-kV transmission line upgrades/rebuilds in and around Green Bay. The planned project will also provide the extra transmission capacity needed to fully utilize the upgrades to the Wisconsin-Upper Peninsula transmission corridor which are scheduled to be completed before this project (i.e., Plains-Stiles and Cranberry-Conover).

The Clintonville-Werner West 138-kV line will be strung primarily on Morgan-Werner West 345-kV line structures. The planned project will provide significant system benefits. These benefits include additional reduced loading on the Highway V-Preble-Tower Drive 138-kV line, the North Appleton-Lawn Road-White Clay 138-kV line, the Badger 138/115-kV transformer, the Badger-Caroline 115-kV line and facilitating a future de-energized rebuild of the Pulliam-Stiles double-circuit 138-kV line, which would not be possible under current system conditions. In addition, the Clintonville-Werner West line will provide a second 138-kV source to the city of Clintonville.

Two-1.2 MVAR distribution capacitor banks will be in service at the Sister Bay 69/24.9-kV Substation in 2008. The addition of these capacitor banks will boost the voltages in the area under normal and single-contingency conditions until longer term solutions are in place. The long-term solution may include constructing a Canal-Dunn Road 138-kV line (2012) and a Dunn Road-Egg Harbor 69-kV line (2016) which were delayed due to the planned installation of these capacitor banks. The long-term solution will address not only the potential low voltages in the area under normal and single-contingency conditions but also the potential overloads of the 138/69-kV transformers and 69-kV lines in the area under single-contingency conditions (See Zone 4-2013 study results).

Rebuilding the Crivitz-High Falls double-circuit 69-kV lines is planned for 2009 in order to address the potential overloads on the Pioneer-Sandstone 69-kV line or the Crivitz-High Falls 69-kV line and to provide voltage support in the area under normal and single contingency conditions. The 2009 in-service date is possible because of the interim load-shifting measure from the Sandstone 69-kV to the Crivitz 138-kV Substation in 2008. Due to the non-coincident nature of the load for this area and the hydro generation patterns in the area, the potential overloads and low voltage issues may also occur during off-peak periods.

A new 138/69-kV transformer at the existing Menominee 69-kV (2008) is under construction to address West Marinette and Roosevelt Road 138/69-kV transformer overloads under single-contingency conditions. The placement of a 138/69-kV transformer at Menominee, rather than replacing the transformers at West Marinette or Roosevelt Road will provide greater geographical diversity, while adding the needed capacity. In addition, it will provide operational and maintenance flexibility during the double-circuit outages of the West Marinette-Menominee 138- and 69-kV lines.

As discussed in earlier Assessments, the rebuild of the Sunset Point-Pearl Avenue 69-kV line would address the potential overload of the line under single-contingency conditions. The project is planned for 2009.

A new 138-kV substation at Cedar Ridge (2008) is currently under construction to accommodate the 98-MW Wind generation interconnection in Fond du Lac County. The existing Ohmstead-Kettle Moraine 138-kV line will be looped into the new substation.

The Mishicot Substation will be relocated in 2009 to accommodate a 99-MW wind generation addition in Kewaunee County.

In the summer of 2008, the North Appleton-Mason Street and North Appleton-Lost Dauphin 138-kV lines were uprated to accommodate the transmission service request associated with the Fox Energy Center wind generation.

An uprate of the North Appleton-Fox River 345-kV line was recently completed. Significant clearance violations on the line were identified in recent LiDar clearance studies. As a result, uneconomic generation redispatch was needed to relieve the loading on the line in anticipation of a North Appleton-Kewaunee 345-kV line outage. The situation became aggravated when the ATC system experienced heavy east-to-west biases in system flow. The project provides additional capacity to the line and addresses the loading issue.

New to this Assessment, installing a second 138-kV reserve auxiliary transformer at Kewaunee and removing the existing tertiary auxiliary transformer (TAT) load from the 345/138-kV transformer T10 is proposed for 2009. Implementing the project will increase the offsite power reliability and provide better operations and maintenance flexibility. With the existing Kewaunee TAT connection on T10, a T10 failure will result in the reduction of the number of offsite power sources to one independent source. This will result in the Kewaunee nuclear unit entering a 7-day Limiting Condition for Operation (LCO). If T10 cannot be replaced or repaired within those 7 days, the unit would be required to shut down. In general, the repair/replacement for a faulted transformer takes more than 7 days. Furthermore, the existing TAT connection makes T10 unavailable for maintenance outside of a refueling outage.

Also, new to this Assessment, significant new loads forecasted at the Sobieski 69-kV Substation would result in unexpected low voltages at Suamico and Sobieski 69-kV substations under normal and single-contingency conditions and heavy flow on the Pioneer-Sobieski 69-kV line under single-contingency condition. However, recent information from Wisconsin Public Service Corporation indicates that the new load will not be interconnected, and the load forecast at the substation will be revised in future Assessments.