Refer to Table ZS-2 and Figure ZS-2

Summary of key findings

• Continued low voltages and overloads on the transmission facilities around the Tomah area.  The 69-kV transmission corridor in the central part of Monroe County is particularly sensitive to a west-to-east system bias.  Thus, this area will require reinforcements be implemented to reliably serve load in the future.
• Potential voltage and loading issues on the transmission facilities in the Stevens Point and Wisconsin Rapids areas are beginning to appear under certain contingencies. Further analysis and study work is required to define the need and identify potential reinforcements.
• Low voltages and overloads for critical outages in the Castle Rock Lakes area may be adequately addressed in the short term with generation redispatch.  However, transmission reinforcements such as the expansion of existing capacitor banks and the rebuilding of existing 69-kV transmission lines will eventually need to be implemented.
• Low voltages and overloaded 69-kV facilities around the Berlin\Ripon area will necessitate that a combination of reinforcement projects be implemented.

Several potential reinforcements have been evaluated to address the low voltage and thermal overload issues in the Tomah area. Furthermore, there is a need for periodic separation of the ATC-Dairyland Power Cooperative facilities at the Council Creek Substation. These reinforcements include a phase-shifting transformer, series reactor, capacitor banks, operating guides, or a combination. To address the near-term pre- and post- contingency issues, capacitor banks were installed on the Council Creek 138-kV bus in 2006 in conjunction with the continued use of the Council Creek operation guide. We are currently working in cooperation with Dairyland Power Cooperative and Xcel Energy to develop a more comprehensive long-term solution to address reliability issues in the Tomah area as well as the limitations along the Monroe County-Council Creek transmission corridor. The proposed solution will be to replace the existing 69-kV circuit between the Monroe County and Council Creek Substations with a new 161/69-kV double-circuit line in 2012.

Marginal voltages were observed in the Wisconsin Rapids area on the 138-kV system between the Sigel and Saratoga Substations for most critical contingencies.  Also, at the Rocky Run Substation one of the three bulk power transformers is becoming heavily loaded under contingency.  Although further study is still needed to better understand the system issues behind these new findings, they appear to be associated with local load-serving issues.  Thus, one recently announced large industrial plant closure in this general area will help defer the need to implement a system reinforcement to address looming system limitations.

Low voltages and overloads in the Castle Rock Lakes area will necessitate a combination of reinforcement projects be implemented.  The proposed reinforcements include the expansion of the existing Mckenna capacitor bank, the rebuild of the Castle Rock–Mckenna 69-kV circuit and the load shift associated with an ACEC Badger West T-D interconnection. Additionally, redispatch of local generation may help alleviate these issues.

To address low voltages and overloads elsewhere within Zone 1, additional capacitor banks will be needed at the Ripon Substation in 2016 and an additional transformer will be installed at the Wautoma Substation in 2017.

In response to a customer request for a new distribution interconnection, a new 69-kV transmission line will be placed in-service in 2014 from the Ripon Substation to the Metomen Substation to connect the new Southwest Ripon Substation.