The paper deals with the development and study of the method to determine the parameters of the balancing devices of three-phase power supply systems, based on the analysis of the system operation mode with the subsequent graphoanalytical determination of the parameters of balancing and full compensation of reactive power. Complex methods of analysis of linear electrical circuits are used. The proposed method allows obtaining in a graphoanalytical way a numerical solution to the problem of balancing currents in a line and compensation of reactive power in a three-phase power supply system with an asymmetric load. The calculation results show that the application of the proposed method initiates significant balancing of currents in the lines of a three-phase power supply system. The unbalance coefficient in the reverse sequence decreased from 32.9% to 1.25%. The phase difference between the voltage vectors of the phase EMF and currents does not exceed 0.7 electrical degrees.