Purpose: To propose a method for selecting adjustable EMF values in idling traction substations for a given power, and the justification of this algorithm application on railways electrified with 3.0 kV direct current. Methods: The graphical method was used to ascertain the values of current through voltage, thereby facilitating the calculation of the corresponding EMF values in idling substations. Utilising the calculation and analytical method, the electric current values at the traction substations were established, thus enabling the calculation of the traction substation power. Results: The calculation conducted utilising the graphical method, has elucidated the dependence of the current collector voltage on the electric rolling stock current in the case of constant power. The calculation performed in the MathCAD system facilitates the determination of the nature of the dependence of the traction substation current and power on the distance between the electric train and the substations. Practical significance: The findings of the research demonstrate that the selection of optimal EMF values in idling traction substations enables the reduction of losses of electric power in the traction network. This is of particular significance in the context of heavy and high-speed trains.