What is a one-line diagram?
The one-line diagram is used to convey important information about the power system. topological information about a power system. Most of the electrical power systems in practice are three-phase systems in which each of the three phases is very similar to each other. This similarity enables to show one of three phases. Due to this reason the name one-line is used.
One line diagram is also sometimes referred as single line daigram.
Modeling One line diagram in ETAP.