High Bias Study

The main objective for this study was to determine what limitations, beyond those being addressed with the 2017 10-Year Assessment project list, ATC might see with high biases across the ATC transmission system.

The base model for the study was the 2027 all-project shoulder from the 2017 10-Year Assessment. Nine different biases were applied to the model and then no load loss allowed contingencies were applied. SPS/RAS operation and voltage limitations were not considered in the study. The nine different biases were:

  • Minnesota to ATC
  • Minnesota to Illinois and Indiana
  • Iowa to ATC
  • Iowa to Illinois and Indiana
  • Minnesota and Iowa to ATC
  • Minnesota and Iowa to Illinois and Indiana
  • Illinois and Indiana to ATC
  • Illinois and Indiana to Minnesota
  • Illinois and Indiana to Minnesota and Iowa

The study showed a number of elements within ATC could be limitations under high bias scenarios. The first and second limitations for each bias scenario is shown in table 1.

Bias ScenarioATC First Limiting ElementATC Planning ZoneATC Second Limiting ElementATC Planning Zone
Minnesota to ATCPetenwell – Saratoga 138-kV Line X-431Castle Rock – McKenna 69-kV Line Y-471
Minnesota to Illinois and IndianaArpin – Sigel 138-kV Line X-331NoneNone
Iowa to ATCPetenwell – Saratoga 138-kV Line X-431Castle Rock – McKenna 69-kV Line Y-471
Iowa to Illinois and IndianaPetenwell – Saratoga 138-kV Line X-431Castle Rock – McKenna 69-kV Line Y-471
Minnesota and Iowa to ATCPetenwell – Saratoga 138-kV Line X-431Castle Rock – McKenna 69-kV Line Y-471
Minnesota and Iowa to Illinois and IndianaPetenwell – Saratoga 138-kV Line X-431Arpin – Sigel 138-kV Line X-331
Illinois and Indiana to ATCPetenwell – Saratoga 138-kV Line X-431Bluemound - Butler 138-kV Line 50615
Illinois and Indiana to MinnesotaPoint Beach - Kewaunee 345-kV Line Q-3034Fox River - North Appleton 345-kV Line 68324
Illinois and Indiana to Minnesota and IowaPoint Beach - Kewaunee 345-kV Line Q-3034Fox River - North Appleton 345-kV Line 68324

The study was informational only and no projects to fix the thermal limitations above, or other thermal limitations found in the study, will be proposed in this Assessment. ATC will continue to monitor thermal limitations identified in this study in subsequent Assessments.