The textbook presents the theoretical foundations of the topological method for analyzing the modes of complex equivalent circuits of electrical circuits from the standpoint of the system functions of resistance, based on the matrices of the distribution coefficients of the driving currents. A new topological method for determining current distribution coefficients based on graph trees of a complex circuit diagram is proposed. The issues of determining the system resistance functions of electrical circuits and analyzing their stationary modes are considered, and a new approach to the development of the principles of diakoptics for the analysis of large-scale circuits is proposed. The tutorial is for students, undergraduates, technical universities in the specialty "Power Engineering", and can be useful for engineering and technical personnel involved in the analysis, design and operation of equipment in the electric power industry.