The work is devoted to the problem of providing electrical energy to remote production enterprises in the absence of a centralized power supply. The purpose of the work is to develop decision support tools for choosing autonomous power generation projects from a large number of possible alternatives. To achieve this purpose, a hierarchy of criteria was constructed and a comparative analysis of existing technical and economic solutions in the field of small-scale autonomous energy was carried out. It is shown that when choosing a power generation project for a particular enterprise, there is a fairly large number of alternatives, which makes the use of commonly used decision support procedures based on the hierarchy analysis method/analytical network method (in the classical version) ineffective. An iterative procedure with dynamic changes in feedback between criteria and alternatives is proposed, which makes it possible to reduce the dimension of the supermatrix during the calculation process and, thereby, reduce the time complexity of the algorithms. The effectiveness of the proposed modification of the analytical network method is confirmed by calculations. The constructed procedure for selecting an autonomous power generation project makes it possible to increase the level of scientific validity of technical and economic decisions when expanding the production activities of small enterprises in remote and sparsely populated areas.

Keywords: autonomous power system, decision support, analytical network method

Loads from ice and frost formations on the wires of the contact network worsen the quality of current carrying and contribute to the emergency situation. The article presents the analysis of methods and sets of equipment for diagnostics of ice and frost formations on the wires of the contact network. Elements of diagnostic equipment form an information system, the end point of which is the energy dispatcher's console. It is shown that the composition of the diagnostic equipment is determined by the type of contact suspension and its place of installation. The variety of methods used for diagnostics of ice on wires of the contact suspension shows the complexity of the problem to be solved.

Keywords: contact network, ice formation, loads, diagnostic methods, operation, current collector, working conditions, emergency situation, refinement of methods

The article presents a method for calculating short-circuit currents in a DC traction network. The system of group grounding of supports, considered in the article, is equipped with an additional conductor that improves the working conditions of the entire section of the electrified railway by reducing the resistance of the short circuit loop.

Keywords: group grounding of supports, short-circuit current, electrified railway, traction network, fiber-optic communication line.group grounding of supports, short-circuit current, electrified railway, traction network, fiber-optic communication line

The paper proposes a model of a circuit with a pulsating circulation of a liquid coolant for cooling an oil transformer and investigates the dependence of the heat transfer coefficient on the frequency of the liquid pulsation in the heated circuit. As a result of the experiments, it was found that the pressure amplitude remains practically unchanged up to a frequency of 0.45 Hz, then sharply decreases and at a frequency of 0.9 Hz it is approximately 12.5 kPa. It was also found that in the heated circuit (circuit 1) the temperature difference exceeds the temperature difference in the heating circuit (circuit 2), which is due to the fact that the fluid flow rate in the heating circuit exceeds the flow rate in the heated circuit. The theoretical calculation carried out showed that in the proposed model the heat transfer coefficient reaches its maximum at a pulsation frequency of 0.6 Hz and is 133.675 W/m2K.

Keywords: energy efficiency, oil transformer, heat recovery, heat exchanger, transformer cooling

The article provides a brief analysis of the processes that occur when starting an electric motor. Mathematical relations modeling the process of starting a direct current motor are presented. Graphical dependences allowing to determine parameters of a thermistor providing an optimum start-up of a direct current machine have been obtained.

Keywords: starting current, thermistor, starting rheostat, thermal characteristic, DC motor, boundary conditions, torque resistance, idealized rheostat, heat loss, economical starting

The article gives a brief analysis of thermal processes occurring during the start-up of an electric motor. Mathematical relations modeling the distribution of thermal energy in the thermistor during the process of starting the DC motor are presented. Graphic dependences are presented, which allow to make arrangement of thermoresistors for the starting rheostat and to determine parameters of the starting rheostat obtained in this way. Application of the starting rheostat made on the basis of thermistors, provide an optimal starting of a DC motor.

Keywords: control gears, thermistor, starting rheostat, DC motor, temperature, dynamic characteristic, form of starting current