This article has a training video for Unit Substation (USS) in COMPAS Go to Change incoming. Unit Substations consist of a Primary, Transformer and Secondary.  High Voltage enters through the Primary section and exits through the Secondary. There is always a transformer between the Primary and Secondary. 

When a user needs to change the incoming Left to Right or Right to Left make all changes in the USS configurator.

Move the configured lines in the USS configurator. 

Drag and Drop the  Primary and Switchboard to the required location. When moving lines do not move to the top.  First move the MDP to the second line then move the USS#1 to the bottom. (Similar to moving lines in PowerMod) 

Because the Switchboard is stand alone, users need to change the incoming.  Open the switchboard configurator and Delete layout, change the incoming and save. Run Layout in the USS Layout to see changes.