This article has a training video for Unit Substation (USS) in COMPAS Go for importing line items. 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. 

Configure Switchboard / LV Switchgear and add it to the Unit Substation. (Nested Configurator) Users can also import an existing Switchboard / LV Switchgear configuration from another quote.