One-Line Diagram:

The one-line, or single-line, diagram displays the elements of a circuit through means of single lines and the suitable graphic symbols. The One-line figure display two or more conductors which are connected among components in the real circuit. The one-line diagram displays all pertinent information about the sequence of the circuit, but does not provide as much detail as a schematic figure. Generally, one-line diagram is used to display highly complex systems without displaying the actual physical connections among components and individual conductors.

As an instance, below Figure displays a typical one-line diagram of an electrical substation.

Figure: One-Line Diagram