Purpose. Selection of a rational power supply system for an electric drill based on an assessment of active power and voltage losses in a cable line.Methodology. Research on active power losses in current leads is based on the use of the theory of electrical circuits. On the basis of retrospective methods of reliability study of the main elements of the electric drill power supply system, factors that affect its reliability and efficiency are determined. As a result of mathematical modeling of functioning of the electrotechnical complex of electric drill power supply system with DC link in the mathematical editor Mathcad the change in losses of active power and voltage during the transition from the "two wires -pipe" system to the system with a DC link "one wire -pipe" is investigated.findings. The influence of the structure of the power supply system of the electric drill on the level of power dissipation and voltage losses in the current lead during drilling of wells is investigated. The necessity of transition to an electric drill power supply system with DC link "one wire -pipe" is justified. This power supply system will increase reliability and energy efficiency indica tors.originality. It has been shown for the first time that the active power dissipation and voltage losses in the current lead of the electric drill with the use of the power supply system with DC link "one wire -pipe" are smaller in comparison with the existing electric power supply system, especially when drilling average and lower intervals of wells.Practical value. The developed mathematical models of active power dissipation and voltage losses in the current lead allow us to determine the main indicators of energy efficiency and operational reliability of the electric drill power supply system and fa cilitate the choice of the economic drilling process.