The objective of mechanical calculation of flexible wires of substations and overhead lines is to determine the sag and tension in different climatic conditions. A wire with a uniformly distributed load is considered as a homogeneous flexible thread having the form of a parabola. Concentrated loads from spacers, barrier balls, stubs, taps to electrical apparatus and other elements are replaced with the one distributed over the span. On behalf of a span without tension springs of insulators the action of concentrated loads on the wire is considered, an error is determined when replacing the concentrated forces with the one uniformly distributed along the span by the load. The sag for the equivalent wire is determined with the aid of the ratio of the increase of the sag, due to the presence of concentrated forces. An equation of state has been drawn up which makes it possible to determine the tension after changing the number of concentrated loads, e.g., after installing spacers, hanging the barrier balls, fixing the taps. The dependence of the maximum sag on the number of concentrated forces is given. The definition of the coefficient of concentrated forces as the ratio of the sum of the concentrated loads to the weight of the wire in the span is presented. A relationship between the load factors, the increase of the sag and the coefficient of concentrated forces is established. The formula has been deduced for determining the error in the replacement of concentrated forces by a uniformly distributed load along the span as a function of the number of concentrated forces and the coefficient of concentrated forces. A decrease in the error with an increase in the number of concentrated forces has been demonstrated. A more accurate calculation of mechanical tensions and sag is possible with the use of a vector-parametric method for calculating the flexible busbar of substations and air-line wires, where the design model of wires in the form of a flexible elastic thread is placed, taking into account the spatial disposition of all structural elements.

False operation of the differential current protection leads to tripping of the most important electrical power objects. Fault of current transformer’s secondary circuits is one of the most often cause of false operation of the differential current protection. Early determination of this malfunction increases the reliability of the differential current protection and reduces the number of false trips. In the present article the methods of secondary open circuit determining for the differential protection are described. Some of the methods react instantly to the malfunction of secondary current circuits, and the other part identifies fault after a certain time delay. Each of considered methods has its advantages and disadvantages. A new method for determination secondary open current circuits based on the analysis of increments of the RMS values of differential and braking currents has been proposed. In this case, increments are calculated for half the period of the industrial frequency, which provides quick fault determining. The use of the sum and the difference between the increments of the brake and differential currents makes it possible to determine the open circuits in the most sensitive way. The method can be adapted to work with any type of differential protection, including transformer protection. The evaluation of the increment of the RMS current value is performed taking into account the transient process in the Fourier filter. With the aid of a computational experiment, the error limit of such an estimate is determined. The block diagram of algorithm of determination of open circuits on the basis of the analysis of increments of the acting values of brake and differential currents is presented; the principle of its functioning is described. The parameters of operation are determined. The limits of sensitivity of the method are determined, too. The time characteristics of the algorithm have been determined by the method of computational experiment with the of the MatLab Simulink simulation environment.

The mathematical modeling of generators of linear and reciprocating types with electromagnetic excitation resulted in obtaining the equivalent electrical circuit and diagrams of magnetic circuit of generators as well as the expressions that describe the electromagnetic processes in generators of linear and reciprocating types with electromagnetic excitation is presented in the article. Mathematical models of generators of linear and reciprocating types with electromagnetic excitation take into account the geometrical parameters of the magnetic system of generators, effect of the armature reaction, the unequal distribution of the magnetic field in the magnetic system of the generators and the dependence of the scattering coefficient and the fringe effect (in linear generators) and buckling (in the reciprocating electric generators) on the coordinates of the movement. An evaluation of the effectiveness of the generators of linear and reciprocating types with electromagnetic excitation was performed that demonstrated that the efficiency of the reciprocating generator with electromagnetic excitation is limited to the amount of movement of the moving part of the generator that can be considered as a drawback of this type of generators. Therefore, the reciprocating generator with electromagnetic excitation is more effective to be used in a small value of the working stroke of the movable part of it or in conjunction with a linear generator as a compensator of the end effect in reciprocating motion. In the linear generator the rate of change of inductance and mutual inductance throughout the movement of the moving part is practically constant. So if an increase of the magnitude of the working stroke of the movable part takes place the benefits of the linear generator are undeniable. However, it should be noted that a reduction of the stroke magnitude of the movable part of the linear generator is limited by constructional dimensions of the magnetic system of the generator, which reduces its efficiency at low value of the working stroke of the movable part.

The paper presents a brief analysis of the conducted researches of the asynchronous executive motors and the induction motor, as well as the design of the asynchronous executive motor with a hollow perforated rotor. The basic relationships for determining the geometry of the rotor that directly influences the energy performance of the electric machine are also presented. The calculations to determine the geometry of the windows, located within a part of the active length of the stator package in the zone adjacent to the solid frontal area of the surface of the barrel from the side of its end face that is opposite to the bottom of the rotor barrel. In an asynchronous motor with a hollow perforated rotor improvement of energy performance (increase of maximum torque, efficiency and cosj of the engine) is achieved. These advantages are provided by the fact that the windows in the hollow rotor barrel are located within the part of the active length of the stator package in the zone adjacent to the solid frontal section of the rotor barrel surface on its end face that is opposite to the bottom of the barrel. In accordance with the design of the hollow rotor, the bottom of the barrel of one of the ends acts as superconducting short-circulating ring, therefore the ratio of increase in resistance (caused by the transverse edge effect) depends on the distribution of the rotor currents in the area adjacent to the solid frontal portion of the surface of the barrel on end that is opposite to the bottom of the barrel. In the analysis of current density distribution in a hollow rotor with the axial length L', all electric constant and geometric dimensions that are taken into account in the calculation are known values. Arbitrarily set constants are the primary currents and the rotational frequency of the rotor. With the rotation speed increase, due to the presence of the windows on one end face of the rotor and to the impact of the bottom of the barrel on the other one, the elementary currents of the rotor within the active length of the machine boring would be directed mainly in the axial direction, including the cases of comparatively small slippage that corresponds to the small frequency of the alternating magnetization of the rotor material. I. e. a certain part of the active surface of the rotor on the end that is opposite to the bottom of its barrel would not function as the frontal part of the winding while reducing the frequency of currents in the rotor material. This provides an increase in the active component of the rotor current that is proportional to the electromagnetic torque of the motor. Correspondingly, the frontal parts of equivalent winding of the hollow rotor (through which the currents do not generate torque) would not be spread at high rotational speeds to the area of the active length of the machine.

Over the past 20 years there have been significant changes in the customer requirements for housing in the countries of the former USSR. Besides, new materials and construction products, such as the ones for sealed windows and balcony doors have appeared in the market. The number of vacant flats with the heating off in the winter significantly increased that may cause condensation on the surfaces of interroom partitions and the formation of mold. Meanwhile, the requirements for lower energy consumption are constantly increasing, that is especially pronouncedly manifested in the growth of normative values of thermal resistance of enclosing structures of buildings and in the increased interest in the use of secondary energy resources extracted from the air and effluent wastewater. The present article describes the method to prevent moisture condensation on the fencing of adjacent premises with different temperatures containing heating systems and the use of waste heat removed from the room exhaust air. For quick emergency switching of in-house systems of heat and gas supply to outdoor mobile sources of heat and gas it is recommended to install special taps with connectors insulated in special niches in the walls or other parts of buildings considering the possibility of placing them close to the outer mobile sources of heat and gas. In the case of heating the building with the aid of a roof gas boiler or by doorto-door heaters fueled by gas, a single pipeline (collector), equipped with an additional device for the connection of emergency gas supply is being put along the wall. In order to reduce specific heat consumption for heating of buildings it is recommended to increase the net enclosure volume of buildings and to improve their form in various ways, including by combining two or more adjacent low-rise buildings in one secondary building with increasing height and with the broadening of either or each side for modernization and reconstruction. The dimensions of the reconstructed building are accepted as the maximum possible, and their proportions (in any number of merged buildings) – as providing tend of shapes to spherical or equicylindrical, or cubic – in any combination.

In a number of foreign countries, vortex heat generators have become widespread in decentralized heat supply systems. For Belarus, vortex heat generators are quite new sources of heat supply. The article considers the possibility of using vortex heat generators for heat supply systems for residential, public and industrial buildings. Vortex heat generators are based on the principle of cavitation in a turbulent water flow. For many devices cavitation is not desirable, but in a vortex heat generator it is used as a favorable phenomenon. The authors carried out a series of full-scale experiments to determine the efficiency of the “VTG-2.2” vortex heat generator when different operating modes were applied. The performance of the vortex heat generator can be estimated by the energy conversion factor. Energy conversion factor is the ratio of the amount of thermal energy that a vortex heat generator generates to the amount of electrical energy consumed. Experiments conducted in a number of research organizations (including the National Academy of Sciences of Ukraine and MPEI) have demonstrated that energy conversion factor can exceed 1. The authors conducted experimental tests with the use of an experimental installation simulating a heat supply system. According to the obtained experimental data, the energy conversion coefficients for each mode were calculated. The constructed graphical dependencies clearly demonstrate that, with increasing rotational speed of the vortex heat generator, the efficiency of its use increases. The highest energy conversion factor value was 61.1 % with a rotation frequency of 40 Hz. It was also found that with increasing the rotational speed of the vortex heat generator, a significant increase in noise and vibration occurs.

This work is a fragment of ongoing research aimed at creating a comfortable information environment that provides access to the publications of international scientific journals and other periodicals and continuing publications that are necessary to support qualitative performance of research in Priority Directions of the Research and Technical Activities in the Republic of Belarus for 2016–2020. During the citation analysis-based selection of the world scientific serial publications apposite for a qualitative performance of research in energy security, energy conservation and energy efficient technologies and techniques with the use of the data of Journal Citation Reports® (which basic results are available at: https://figshare.com/articles/energy_sec_xlsx/5606053/2) a noticeable amount of non-serial items was also found out in addition to serial publications, as well as some publications that, though being serial, did not look typical to be used in the research activities. Individual consideration of each such “exotic” information source confirmed, however, that their noticeable citedness by the world experts in power engineering looked quite natural. Moreover, it becomes clear that these (apparently wrongly) reflected in Journal Citation Reports® information sources are, however, not an “information noise”, but a useful addition to the “professional reading” of power engineering experts. Since these sources are publicly available via the Internet, it was decided just to recommend them for inclusion in the “professional reading” of the CIS power engineering experts, providing the latter with URLs and brief recommendations for the use. All the mentioned data is given in the present article. As for the species structure of the information sources included in our reference list, there are: a database with online access; web-sites of news agencies; web-site of the International Energy Agency; statistical yearbooks and the electronic resources exposing them, annual reports of governmental and intergovernmental organizations; the online version of the newspaper (“The Guardian”).

Heating grids are intended for transportation of thermal energy from heat sources to consumers. On the balance sheet of the power supply organizations of the state enterprise “Belenergo”, which is part of the Ministry of Energy of the Republic of Belarus, there is more than 6500 km of heating grids in one-pipe terms. Analysis of the results of complex surveys of heat supply enterprises in Belarus shows that heating grids are one of the most unreliable elements of the heating system of the city today. The main reason of disturbances in operation of heating grids (about 90 %) is the local external corrosion that manifests itself in the form of fistulas and breaks of metal of network pipelines. The most quickly, all other things being equal, external corrosion affects those pipelines in which there is a direct contact of the unprotected surface of the pipe with the ground. In addition, in the process of operation of heating grids possible damages might happen that are associated with the breakdown of stationary pillars, with the gaps of the buildings cast iron valves, with the breakdown of the thread of the discharge valves, with damage of compensators, etc. According to ORGRES statistical studies, most of the damages (up to 70 %) of pipelines in Russia (as well as in Belarus) are associated with corrosion. Despite the estimated service life of the pipelines (up to 30 years), the sources of centralized heat supply in Russia pipes are 70 % worn out. With this regard, losses significantly increased in heating grids. General wear and tear of the heating grids of Ukraine in 2010 was 70 %, while losses in heating grids reached up to 30 %. Every year, the situation will only get worse. Thus, external corrosion of heating grids is one of the main factors determining reliability of operation of systems of heat supply.