The article shows that the operation modes in three-phase four-wire 0.38 kV electrical networks are objectively associated with unbalancing power consumption. As a result, significant additional electrical energy thermal losses occur in the neutral conductor’s internal electrical networks and external electrical networks l elements, which not only increase the electrical energy consumption, but also create conditions for the fire-hazardous occurrence single-phase short circuits. A mathematical model is proposed, an algorithm and a program for calculating the limit zero sequence values flows in external neutral conductors and internal 0.38 kV electrical networks are developed. Numerical calculations are made and tabular these limit values data for different conductors’ sections made of various conductive materials are presented. The unbalancing operation modes calculations in operating external and internal 0.38 kV electrical networks have been made, on the basis of which the proposed methodology has been tested. The technical means use effectiveness for the operating modes balancing in existing electrical networks with unbalance power consumption is proved.