This tutorial provides an introduction to single-line electrical diagrams of electrical installations, the elements of these diagrams, and the technical characteristics of the elements indicated on the diagrams. An example of calculation of power losses in power lines using the specified characteristics is given. The appendix contains basic information from the State Standard of Russia on the rules for the execution of electrical circuits as well as the Standard of the Federal Grid Company "Rules for the design of normal circuits of electrical connections of substations and graphic display of information by means of CAS and APCS"