Residential and industrial buildings with large territorial dimensions, have mainly radial power supply schemes, which feed a large number of small and medium capacity 0.4 kV induction motors. For their power supply copper or aluminum cables of small cross-section (with high active resistance) are used. Calculations of electricity losses in such lines show significant values. In order to reduce active power losses in 0.4 kV cable lines, the optimization problem of minimizing active power losses in the radial power supply circuit is solved by optimal distribution of reactive power of a given value between compensating devices. The single-line scheme of power supply of a group of pumps of technological installation of petrochemical production is considered, the mathematical model of the optimization problem on criterion of minimum of active losses in power lines from reactive power flow is made, which limitations are presented as a system of linear algebraic equations. Results of distribution of optimum values of reactive power between compensating devices of asynchronous motors at maintenance of the set tg φ are received. The quantitative estimation of active power loss reduction in power lines at use of capacitor units, which reactive power is optimally distributed, is given.