Refer to Table ZS-4 and Figure ZS-4

• Voltage and thermal issues remain in Zone 1 under contingency conditions.

Following are the results of the 2023 contingency analysis (NERC Category B or

TPL-002-0 conditions) performed on Zone 1.  Please note that because this is a 15-year projected scenario, new projects were not necessarily added to the Assessment based upon these results. However, we will continue to monitor these situations in future scenarios to determine which project(s) may solve these potential issues.

An outage of the Rocky Run 345/115-kV transformer #2 or the Arpin-Sigel 138-kV line results in the Rocky Run 345/115-kV transformer #3 exceeding its summer emergency rating.  Transformer #3 is the largest of the three 345/115-kV transformers at Rocky Run, but the overload of this unit occurs first because this unit is the only one of the three transformers at Rocky Run that is not capable of carrying additional load for short durations. Thus, the summer normal and emergency ratings are the same.

The Plover–Coyne 115-kV circuit is approaching its summer emergency rating for an outage of the Arpin–Sigel 138-kV circuit. 

The Chaffee Creek–Coloma Tap 69-kV circuit exceeds its summer emergency ratings for an outage of the Necedah Tap – Big Pond 69-kV circuit.

The Harrison 138/69-kV transformer will load to 97% of its summer normal rating under intact system conditions.  The loading of the transformer is not yet a concern under first contingency system conditions.

Low voltages are being shown on the 69-kV circuit between Portage and Montello for the Portage-Lakehead Portage or Lakehead Portage–Endeavor Tap 69-kV circuit outages.

Summary of Compliance with NERC Standards

The mitigation plans, planned, proposed and provisional projects identified for Zone 1 in this Assessment will allow the ATC system in Zone 1 to meet NERC standards TPL-001, TPL-002, TPL-003 and TPL-004 in each of the four years 2009-2013, and for the 2014-2018 planning horizon.