A single-line diagram can also be used to show a high level view of conduit runs for a PLC control system.OverviewIn, a single-line diagram (SLD), also sometimes called one-line diagram, is the simplest symbolic representation of an electric power system. A single line in the diagram typically correspond. The lines in the single-line diagram connect nodes – points in the system that are "electrically distinct" (i.e., there is nonzero between them). For sufficiently large systems, these points represent p. The theory of three-phase power systems tells us that as long as the on each of the three phases are balanced, the system is fully represented by (and thus calculations can be performed for) any single phas.