This is a three-phase bus model.
A bus represents a node in a power system. Therefore, this model can be used to verify voltage magnitude and angle in the three-phase nodes of the system.
Although it is not necessary, it is extremely recommended to connect one bus model between two other three-phase models.
Please, check if this bus model is the appropriate one for your system. For the connection of two- or single-phase models, two- or single-phase buses might be a better fit.