A branch connects two or three nodes. Unless the branch is a transformer, the nodes must have the same voltage. Only a three winding transformer can connect three nodes.
A branch can be added by selecting two (or three) nodes and choosing the appropriate branch type from the ribbon menu Insert | Branches.
Each branch can be assigned to a field at a node. The fields have to be defined in the node form before they can be assigned to a branch.
See:
•Line
•Link