I'm trying to create connectivity rules between a 115kv electric line and 46kv line, the rule would be these lines are not allowed to be connected together edge to edge or end to edge. I can't seem to figure out how to model this without allowing a junction connection. any ideas?
UN connectivity rules must be positive and inclusionary. You can't define negative network rules. In your case, you don't need to define any rule (assuming your 115kv and 45kv lines having different asset groups or asset types), the system itself not allowed to snap these two lines endpoint each other to connect.
For more details please refer this link - Feature restrictions—ArcGIS Pro | ArcGIS Desktop
Hope this will help you.
I think the best analogy with a Geometric network would be the concept of a GN's Abstract Class >> Feature Class >> Subtype would then map to a UN's Feature Class >> Asset Group >> Asset Type.
The GN and UN aren't like for like so categorizing your network assets will require a bit of thought.
Hope this helps