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The thermal impact of cable power lines and structural materials of cables on the environment has been considered. A quantitative evaluation of the thermal impact of electrical cables with cross-linked polyethylene insulation on the environment was carried out using the Elcut program. Analysis of the temperature field near the loaded cable line of 10 kV demonstrated high values of soil temperature that negatively affects its redox potential and living organisms. To evaluate the environmental impact of electrical cable materials, an approach has been developed that takes into account not only the toxicity of the materials but also their volumetric content in the cable. Cable lines with cables with traditional paper-oil insulation cause more damage to the environment than cable lines with cables, insulated with crosslinked polyethylene. The environment, in turn, also has an impact on the electrical cables: the values of long-term permissible load currents depend on the ambient temperature (when laying cables in the open air, in an earthen trench or in cable rooms). The impact of solar radiation on the thermal conditions of the electric cable is estimated. A comparative analysis of the complex environmental impact of electric cables with traditional insulation and insulation of crosslinked polyethylene demonstrated that unarmored cable with crosslinked polyethylene insulation at a voltage of 10 kV (regardless of the type of its shell) causes less damage to the environment than the same traditional cable throughout the considered temperature range on their surfaces.

The assessment of the suitability of cables of 6–110 kW with XLPE insulation in comparison with cables of the same voltage but possessing paper-oil insulation has been fulfilled on the basis of the method of multi-objective optimization that makes it possible to account not only the quantitative characteristics (of reduced costs), but also qualitative ones. As an indicator of the reliability of the cable line the maximum mean time to failure (the value inversely proportional to the parameter of succession of failures), which is an order more for cable lines with XLPE insulation than for cable lines with paper insulation, is adopted. A comprehensive assessment of the convenience of installation of cable lines revealed that the installation of cable with XLPE insulation features a 1.2–1.6 times easier installation as compared to three-wire (voltage 10 kW) and 1.4 times easier installation as compared to single-core oil-filled cables (voltage of 110 kW). The efficacy of the cables 6–110 kW with XLPE insulation is proved on the basis on the method of multi-objective optimization, that took into account as the costs for the construction and operation of cable lines and the reliability of its operation, ease of its installation and other quality indicators. If the goals taken into account are considered as equally important, the polyethylene-insulated cables for a voltage of 10–110 kW is more efficient as compared to three-wire (voltage 10 kW) and solid (110 kW) cables with paper insulation. Herewith, the cost of the cable with XLPE insulation may exceed the cost of cable with paper insulation up to two times. If the most important aim is to provide the minimum reduced costs for the construction and operation of the cable line, the use of cables with XLPE insulation for voltage of 10 kW is most advisable in individual cases.

The assessment of the suitability of cables of 6–110 kV with XLPE insulation in comparison with cables of the same voltage but possessing paper-oil insulation has been fulfilled on the basis of the criterion of reduced costs. Thus, the comparison was undertaken between cables of various design and material of insulation: three-core paper insulated ones vs. three-core XLPE insulated ones; three-core paper-insulated ones vs. solid wires with XLPE insulation; single-core oil-filled cables of 110 kV with paper insulation vs. solid wires of 110 kV with XLPE insulation. The increase in long-term permissible current loads for cables with XLPE insulation because of the larger permissible temperature of heating in comparison with cables with paper-oil insulation complies with as would increase in the cross-sectional area of cable cores (equal to 0.61 from the original) and therefore reduces the cost of the cable by reducing the cost of manufacture of conductors. The reduced costs of the construction and operation of cable lines with XLPE insulation (accounting the increase in the cost of a cable 1.2 and 2 times as compared with the cost of a cable with three-core insulation), despite the decline in the cost of manufacture of conductors and the reduced annual operating costs (9 % and 17 % respectively of cable lines of voltage of up to 35 kV and 110 kV), occurred to be more than the reduced costs of the construction and operation of cable lines with paper insulation. Currently the cost of one meter of cable with XLPE insulation is less than the cost of cables of AAB, CASB, AASv types of a voltage of 10 kV with aluminium cores, that ensures their undeniable efficacy.

This article discusses the factors that affect the electrical resistance of the current spreading of the grounding device. The issue of the electrophysical parameters of the soil that affect its resistivity and the consideration of such parameters in the design of grounding devices is considered. It is shown that keeping moisture in the near-electrode space of the grounding electrode, as well as maintaining it at a certain level, facilitates improving the quality and reliability of the grounding. A relationship has been established between the ability to retain moisture and the magnitude of seasonal fluctuations in the electrical resistance of the soixl, and also the season factor, which takes into account changes under different climatic environmental conditions. The issues of application of various methods of reducing the resistivity of the soil during mounting of grounding devices are considered. One of the main ways to reduce ground resistance is the use of solutions of various mineral salts. This method is not optimal, as it accelerates the corrosion processes in the materials of the ground electrodes. Therefore, the paper also considers other ways to reduce the resistance of the ground loop; in particular, the authors propose a method for reducing the resistance of a grounding device based on the method of partial replacing the soil in the near-electrode region with a mixture with a lower resistivity capable of collecting moisture based on graphite and hydrogel. This type of mixture is environmentally friendly when used, as well as it is non-aggressive to the material of the ground loop. The principle of operation of this mixture is based on the fact that the hydrogel makes it possible to stabilize the moisture at the site of laying the circuit, while graphite increases the overall conductivity of the mixture. The paper presents the results of laboratory studies, which have been carried out in accordance with GOST 9.602–2016. For this purpose, control samples were placed in containers made of a non-conductive material (plexiglas) and dependence of resistivity on moisture, temperature, specific content of graphite and hydrogel was measured. The article presents graphs of the dependences of the mixture specific resistance on moisture, temperature, and the quantitative content of the hydrogel. From the results obtained, it can be concluded that the mixture in can be used in the energy sector to improve the reliability of electrical installations and ensure electrical safety.

A separate generating complex is considered in this paper. The main feature of the complex under consideration is its functioning during the control period when the fuel resource is severely limited. The main function of the complex is the production of electrical and heat energy for the needs of the consumer. A control model for production has been developed for two scenarios, viz. of the unconditional provision of the consumer’s needs with electric energy and of the mandatory implementation of the schedule for the release of heat energy. The features of the implementation of the model for a separate thermal power plant (mini-thermal power plant) with a guaranteed supply of electric energy to the consumer are considered, cogeneration modes are substantiated in conditions of a limited fuel supply, regardless of the consumer category. An optimization option is shown when choosing an additional source of heat to meet the needs of the consumer. In the case of choosing a renewable energy source (RES), the management of the ‘cogeneration – RES’ complex according to the proposed strategy allows minimizing the required RES capacity. The basis of production management is the mathematical model of the generating complex, presented in our paper. In terms of describing the behavior of a complex physical system as a whole, an ener-gy approach (Hamilton's method) was used, which turned out to be very convenient for solving the problem, since the variational principles do not depend on the choice of a coordinate system. The description of the turbine plant as an object included in the generating complex and largely determining the relationship between fuel consumption and the amount of electrical and ther-mal energy produced is made with the unconditional fulfillment of the following requirement: fuel consumption is a function of the state of the system. The proposed cogeneration strategy in the conditions of a severe limitation of the amount of fuel does not depend on the type of fossil fuel used and is not tied to the control period calendar dates.

Currently, the topical trend in the development of energy complexes in a number of countries is the expansion of the solid fuel use, which is largely provided by the use of various types of local renewable fuels. The latter often have high thermal properties (heat of combustion, ash content, etc.), but have low or poorly predicted physical and mechanical characteristics (strength, granulometric composition, etc.). These circumstances practically make stable and efficient operation of automation systems, mechanization of transportation of pellets, and technological processes of boilers impossible. The formation of a composite fuel with specified physical and mechanical properties provides a solution to this problem. The structure of the composite fuel based on peat, sawdust, cellulose and modifier was established at the previous stages of our work. However, in case of a given composition, the physical and mechanical characteristics depend on the operating and technological conditions for obtaining granules. In this paper, a statistical and experimental study was carried out aimed at finding rational technological conditions for granulating and drying composite fuel particles with a given mass ratio of components. To prepare fuel pellets of a given size from the initial fine-fraction components, a laboratory installation was used, the main elements of which were a Z-shaped mixer, a screw granulator, and a fixed bed dryer. The influence of independent variables on the strength and final moisture content of finished pellets of composite fuel was determined within the framework of a full factor experiment. The paper presents graphical images of response surfaces characterizing the specified influence of variable factors. The obtained regression dependences describing the influence of factors on the target properties of granules are linear in nature. The latter limits the possibility of using gradient optimization methods and creates the need to search for rational conditions, taking into account the limitations caused by the technical and economic parameters of obtaining finished fuel pellets.

Modern development of society and the economy is generally accompanied by abandonment of non-renewable fuels in the system of existing attitudes toward environmental issues and resource conservation. The paper presents the results of complex operational tests of КВм-2.0 water boilers with automatic stoker and КВр-0.4K at heat supply facilities of the Arkhangelsk region under the typical operating conditions on coal, fuel mixtures, and also peat briquettes and sod peat. Experimental work was carried out using modern methods and advanced technical means. Within the framework of the research on the conversion of boilers to peat fuel, balance experiments were carried out; technical, economic and environmental performance indicators were obtained; the selection and analysis of focal residues were carried out, fine solid and soot particles polluted into the environment were studied in detail. The paper presents graphs of changes in gross efficiency, heat loss with exhaust gas, heat loss with incomplete combustion, and concentrations of sulfur and nitrogen oxides during the cycle between loading peat briquettes into the КВр-0.4K boiler, as well as graphs of changes in the heat balance components and gross efficiency all boiler units under investigation. The conversion of heat generating plants to peat fuel combustion makes it possible to achieve a significant reduction in emissions of solid and soot particles without upgrading ash-collecting plants. Complex experimental studies conducted of existing hot water boilers with a nominal heating capacity of 0.4 and 2.0 MW have shown the possibility, as well as the energy-environmental efficiency of burning briquetted and sod peat in the combustion chambers of these heat generating plants.

As in the whole world, there are regions in Russia that experience heat supply difficulties, mainly due to the high cost of fossil fuel as well as to growth of energy resources cost and polluting emissions. In this regard, search for solutions which would provide energy saving with an increase of energy, commercial and ecological efficiency of modern heat supply systems is becoming vitally important today. One of them is the development and use of special types of energy including renewable energy sources, wind energy in particular. Accordingly, the paper presents one of the possible solutions to the heat supply problem which are directed at meeting the whole region’s heat demand through the joint use of wind power plants with a boiler room operating on fuel oil. The study assessed the efficiency of constructing of wind power plants with a total capacity of 1.7 MW for the heat supply needs of a settlement, which is located on the Barents Sea coast in Russia. The selected area is characterized by an average annual wind speed of 7.0 m/s and a long heating period (9–10 months a year). The assessment showed that the wind power plant construction is financially reasonable, as additional profit can be generated by the end of the wind power plants scheduled service life that make up the half of primary investments. The results obtained in the paper are expected to make up for the lack of information on the feasibility of wind power plants construction for the heat supply needs, which is very useful for other countries that have similar areas experiencing various heat supply difficulties.

The paper considers the suppression of chaotic oscillations in small energy systems that occur in emergency modes and lead to the phenomenon of voltage collapse, which corresponds to the process of voltage drop in the network, which can be accompanied by a complete shutdown of the affected area. The paper also presents a method that has been developed and that allows changing the spectrum of Lyapunov’s characteristic indicators and converting chaotic oscillations in a small power system to regular dynamic modes. The method of synthesis of control actions is based on the theorem of topological equivalence of hyperbolic nonlinear systems and their linearized models as well as on and the use of numerical integration of nonlinear differential equations describing the behavior of power systems in order to construct a phase portrait and calculate Lyapunov’s characteristic exponents. The results of the work consist in the synthesis of feedback, which ensures the formation of a spectrum of Lyapunov’s characteristic indicators with negative values. The suppression of chaotic regimes occurs by forming a spectrum of negative Lyapunov’s characteristic indicators in a closed system. The parameters of the regulator in the feedback circuit are determined using the modal control method based on the solution of the matrix algebraic Sylvester equation. The solution of the problem of transition from a chaotic regime to a regular movement in a small power system is considered. To test the operability of the proposed method of chaos suppression, the spectrum of Lyapunov’s characteristic indicators is calculated and trajectories in the phase space of the initial nonlinear system and the system with control action are constructed. For energy systems with chaotic dynamics, synthesized feedback makes it possible to suppress chaotic fluctuations and switch to regular modes, thereby preventing the occurrence of emergency modes.

The paper presents studies on saving energy resources by creating conditions and introducing modern energy-efficient technologies and equipment into production activities that allow to develop the production and use of local fuels, including the use of briquetting of combustible municipal and industrial waste. The purpose and objectives of the work are to study trends and analyze the problems associated with the processing and use of various types of combustible waste generated and accumulated in industrial and agricultural enterprises, as well as in the field of housing and communal services. The main directions of national sustainable development strategy concerning energy and resource saving and rational use of natural and secondary resources are considered in the paper. Methods for briquetting multicomponent compositions of combustible wastes with the possibility of obtaining solid fuels have been studied. An innovative production technology developed by the authors is described that makes it possible to process waste products by briquetting with the use of various binders. The results are presented and the analysis of the conducted experimental studies is carried out in accordance with the theory of experiment planning for multicomponent systems, taking into account phase equilibria. A qualitative assessment of the component composition of the briquetted fuel, which ensures the highest density of the briquette and effective performance, is carried out taking into account of the moisture content of the multicomponent mixture. Qualitative indicators of the produced two- and three-component fuels have been determined using differential thermal analysis on the MOM-1500 derivatograph, which make it possible to identify phase transformations and chemical reactions occurring during heating. Comparative analysis of qualitative indicators has permitted to draw conclusions about the possibility of using the developed fuel compositions in operated fuel combustion plants.

One of the directions of development of the electric power industry is decentralization, aimed at improving the reliability of energy supply, reducing losses during transmission of electric energy and ensuring energy independence of consumers. It is possible to simulate decentralized power systems, including distributed generation facilities, by implementation of multi-agent systems that allow solving design and control problems taking into account the needs of each participant in the process of production, transmission, distribution and consumption of electricity. The development of distributed generation using a multi-agent approach requires the creation of models for assessing the technical and economic efficiency of decisions made by each agent, both at the strategic and tactical levels. The strategic decisions of agents related to distributed generation include, among other things, the creation of power facilities and power plants based on renewable energy sources. An important factor for making such decisions is the estimation of the capacity factor. However, currently there are no models for its estimation with high reliability. The present paper proposes a new algorithm for estimating the capacity factor for the entire territory of a certain administrative unit and a model for its forecasting based on climatic and geographical parameters. The study was conducted on a data sample of 221 generation facilities (solar and wind power plants) in four oblasts (regions) of the Russian Federation. It has been determined that the capacity factor can be forecasted with a mean error within 4 % for photovoltaic power plants and 9 % for wind power plants. Therefore, it is possible to use the developed algorithm and model both in decision support systems when choosing the location of this types of power plants, and in systems that model the development of power systems using a multi-agent approach.

The paper presents an experimental study of an assembly of five stages of an electric centrifugal pump (ECP) installation, the flow part of which is modified according to the principles of biomimetics, namely using the “lotus leaf effect”. The object of the study was a 5A-35 ECP. The surfaces of the blade systems of impellers and guide devices of stages 5 A-35 were hydrophobized using the method of applying surfactant layers. The degree of impellers hydrophobicity was estimated by the wetting angle average value measured by three drops at three different points on the impeller surface. The impellers surface roughness under study was determined by the arithmetic mean profile deviation Ra and the profile height irregularities Rz. The issues related to the surfactant coating modification effect salt deposition and corrosion were studied. For this purpose, the surfaces of the original and modified impellers were subjected to intensive forced salt deposition as a result of prolonged exposure to saline solution. The conclusion about the samples corrosion resistance degree was made by changing their mass, which was due to the salt deposits formation during 15 hours of stay in solution, as well as using the drop method. Both methods have shown that the surfactant coating can serve as a salt deposition inhibitor, and the pump impeller modified by it has increased corrosion resistance. Thus, during comparative tests, a smaller mass of salt was deposited on the modified impeller sample during 15 hours of exposure in saturated saline solution than on the original sample. This indicates that the surfactant layer prevents the salt deposits fixation on the working surfaces of the pump stage. On the modified sample examined by the drop method, the indicator color changed in 20 minutes, and on the original one – in 2 minutes. Experimental studies have been carried out, during which the operation energy parameters of a five stages 5A-35 pumping package with initial and modified surfactant-coated impellers have been determined. The studies have shown a 2 % increase in efficiency in the pum-ping package of stages with modified impellers. The results of the study can be useful in the oil production, chemical industry, as well as in the housing and communal services sector.

The paper deals with the problem of improving the reliability of DC-DC power supplies with pulse-width modulation. The topicality of the work is related to the importance of power supply issues in modern electronics, since the quality of operation of consumer electrical appliances, including critical ones, directly depends on the serviceability of sources. The object of the study is feedback circuits aimed at stabilization of the parameters of power supply of consumers. Failures of the mentioned feedback circuits most often occurs due to the electronic components degradation under harsh operating conditions as well as under severe mechanical overloads. Such failures are dangerous for uncontrolled increase of power supply output voltage and output current. To avoid this, a new method of reserving voltage feedback signals is presented in the paper which is implemented on the basis of flyback supply topology. Feedback signals are formed from the optocoupler located on the load side and from the auxiliary winding of the power transformer, together forming two independent output voltage control circuits. Only one circuit performs stabilization at any given moment of time. If one of these circuits fails, the second one can simply replace it in its operation. The proposed method does not require any digital signal processing algorithms or microprocessor control modules and can be implemented on the basis of cheap, widely available analog chips that perform pulse-width control of the output voltage. As a result, the problem of sudden feedback loop failure is solved and the reliability of electrical equipment is increased. The validity of the proposed method is confirmed by the results of computer simulation with the use of MatLab-Simulink environment. The obtained results can be used in design of fault-tolerant secondary power supplies that operate in harsh operating conditions.

The paper deals with the problem of increasing the efficiency of the functioning of electric networks up to 1 kV, namely, the possibility of increasing the sensitivity of protections in networks up to 1 kV, which helps to reduce the protection response currents and, accordingly, reduce the cross-section of cable and wire products. The topicality of this problem is shown and the research tasks are defined. Much attention is paid to the concept of selectivity; attention is also paid to the concepts of full and partial selectivity. “Which protective devices can be considered selective?” is a question that is considered and worked out in sufficient depth in the paper. The negative phenomena that occur when ensuring the selectivity of protections in networks up to 1 kV are systematized and described in detail. Based on a comparative analysis of the parameters of circuit breakers with release tripping devices of various types, a solution to this problem is proposed by using circuit breakers with microprocessor and semiconductor release tripping devices. Additional advantages of microprocessor-based circuit breakers are considered and indicated, as well as their disadvantages are indicated, too. The main expected positive effects from the use of circuit breakers with microprocessor release tripping devices are listed, taking into account the fact that this type of circuit breakers is considered as a complex of devices replaced by it. The article can be recommended to employees of electric power specialties working with networks up to 1 kV.

Having proven its effectiveness in finding the best options for energy supply and energy consumption the exergetic method of thermodynamic analysis of complex heat and power systems has been widely recognized in recent years. However, its application is hindered by the lack of appropriate scientific and methodological heat technology support, especially if their application involves not only transformation of energy, but also transformation of substances. Heat treatment of concrete and reinforced concrete products belongs to such technologies. This article presents new scientific results related to the development of exergetic balances of the processes of preparation of concrete mixture in a mixer and heat treatment of a concrete product in a heat-technological installation. For each of these cases, the analysis of exergetic flows was carried out, the structure of the exergy of the concrete mixture and the hardening concrete was determined. Based on the analysis of the literature data on the chemical composition of cement clinkers, cements, and hydration products, new dependences have been proposed for calculating the exergy of the concrete mixture flow and the exergy of concrete under its heat treatment, including all their components, viz. thermomechanical, reaction, and concentration constituents. Absolute energy indicators have been developed. The calculation of the mentioned values was performed on a specific example with the use of the developed scientific and methodological support. In the second part of this paper, the results of the study related to the determination of relative exergetic indicators that allow evaluating the energy efficiency of the processes of heat treatment of concrete products in heat technology installations will be published. The results obtained in this paper can be used for the selection of energy-saving modes of heat-technological equipment intended for industrial heat treatment of concrete products.

The mixed problem for the telegraph equation well-known in electrical engineering and electronics, provided that the line is free from distortions, is reduced to a similar problem for one-dimensional inhomogeneous wave equation. An effective way to solve this problem is based on the use of special functions – polylogarithms, which are complex power series with power coefficients, converging in the unit circle. The exact solution of the problem is expressed in integral form in terms of the imaginary part of the first-order polylogarithm on the unit circle, and the approximate one – in the form of a finite sum in terms of the real part of the dilogarithm and the imaginary part of the third-order polylogarithm. All the indicated parts of the polylogarithms are periodic functions that have polynomial expressions of the corresponding degrees on an interval of length in the period, which makes it possible to obtain a solution to the problem in elementary functions. In the paper, we study a mixed problem for the telegrapher’s equation which is well-known in applications. This problem of linear substitution of the desired function witha time-exponential coefficient is reduced to a similar problem for the Klein – Gordon equation. The solution of the latter can be found by dividing the variables in the form of a series of trigonometric functions of a line point with time-dependent coefficients. Such a solution is of little use for practical application, since it requires the calculation of a large number of coefficients-integrals and it is difficult to estimate the error of calculations. In the present paper, we propose another way to solve this problem, based on the use of special He-functions, which are complex power series of a certain type that converge in the unit circle. The exact solution of the problem is presented in integral form in terms of second-order He-functions on the unit circle. The approximate solution is expressed in the final form in terms of third-order He-functions. The paper also proposes a simple and effective estimate of the error of the approximate solution of the problem. It is linear in relation to the line splitting step with a time-exponential coefficient. An example of solving the problem for the Klein – Gordon equation in the way that has been developed is given, and the graphs of exact and approximate solutions are constructed.

The modern development of power engineering is accompanied by a number of trends, among which one can note the decarbonization of energy production processes; an increase in the share of electricity in the balance of energy consumption due to the deep electrification of industry, transport and heat supply; decentralization of energy sources; an increase in the share of renewable energy sources, including the involvement in the turnover of secondary energy resources and energy from the disposal of organic waste; the development of practice active consumption and prosumerism. For the Republic of Belarus, in which forests are one of the main renewable natural resources and the most important national wealth that ensure the sustainable socio-economic development of the country, its economic, energy, environmental and food security, in the context of decarbonization of the power engineering sector, it is relevant to determine the importance and location of energy generating equipment using local fuels (LF), especially for heating capacities and polygeneration plants. The paper presents the results of a study conducted to evaluate the effectiveness of using mini-CHP plants on LF. The analysis of the archived data of the automated process control system of an operating mini-CHP with a heating ORC unit (Turboden 14 CHP) made it possible to evaluate its maneuverable characteristics with reference to the operating modes of the centralized heat supply system with a predominance of municipal and household heat load in it. It has been shown that the average rate of change in power is 1.5...3.0 % min; respectively, the time to reach rated power under normal conditions exceeds 40 minutes; the time to start the unit from a “cold state” varies from 20 minutes to 2 hours. Therefore the assumption has been confirmed that the studied ORC unit in particular and mini-CHP plants of a similar type as a whole cannot be considered and used as a maneuverable energy source without additional modernization. The conducted numerical study made it possible to show the opportunity of planning effective operating modes of a heating ORC unit in the configuration of the basic thermal circuit of a mini-CHP on LF with the integration of a hydrogen production module into it based on the forecast of the daily schedule of thermal energy consumption and taking into account the dynamics of changes in outdoor air temperature. Conceptual block diagrams of integrated polygeneration systems are also presented; they stand out for the use of hydrogen generation equipment from over-produced electricity during the operation of mini-CHP plants according to a thermal schedule and participation in the coverage of the electric load schedule of the Unified Energy System of Belarus. The use of thermal circuits with thermochemical hydrogen production technology and the operating mode of the ORC unit at rated power is shown to be promising for newly designed mini-CHPs on LF.

There is a large number of factors that affect the long-term permissible load currents of power cables, including environmental conditions, the method of laying, as well as the geometric, thermal and electrical characteristics of the cable structure. The catalogs of manufacturers of power cables with cross-linked polyethylene insulation do not specify the long-term permissible load currents, which would take into account the cross-sectional area of the screen, the presence of aluminum polymer tape and armor made of aluminum wires. These components can have a significant impact on the permissible load due to the currents induced in them during two-way grounding, which leads to additional heating of the cable. The purpose of this study is to analyze the influence of the above-mentioned factors on the long-term permissible load currents. The paper presents formulas for calculating the long-term permissible load current, which take into account the design features of the cables under consideration. The calculations have shown that the permissible load can decrease by 6 % with an increase in the cross-sectional area of the screen from the nominal row by one step. The introduction of an aluminum polymer tape into the cable structure changes the permissible load by no more than 2 %. The presence of armor can lead to a decrease in the permissible load by up to 18 % and its increase by up to 13 %, depending on the section of the core and screen, the method and conditions of laying. The calculation results obtained differ from the catalogdata by up to 25%. While the obtained errorsindicatetheneed to formcoefficientsfor a moreaccuratedetermination of the long-term permissible cable currents.

To organize reliable control over emissions from chimneys of energy facilities, automatic monitoring systems are needed. Equipment is known for monitoring emissions from small-diameter chimneys, but for large-diameter pipes (15 m or more) available in our Republic, there are no corresponding technical solutions. The paper examines the problem of automating the sampling of flue gases based on an electric drive in large-diameter chimneys. To ensure the optimal trajectory of the sampler in the chimney section, it is necessary to use an asynchronous electric motor with a frequency converter and a position sensor. A functional diagram of the control system is proposed, which contains a programmable logic controller for generating the motion mode, as well as a method for calculating parameters and expressions for generating a task signal for continuous sampling mode. Since the range of speed control increases as the diameter of the chimney increases, depending on it, scalar or vector frequency control can be applied. An expression is proposed for calculating the optimal value of the parameter N of an incremental position and speed sensor (encoder), which contributes to a reasonable choice of sensor. The results of simulation modeling are presented, confirming the effectiveness of the proposed method for calculating the parameters of the sampler drive.

Due to the development of electric transport and the growth of “green” energy, electric energy storage systems (ESS) are increasingly being used in the world. The growth of the battery market in the last decade has been 20-30%. One of the ways to increase the efficiency of an electric power storage device is its hybridization, i.e. the use of heterogeneous battery units. The paper examines the features of passive coupling of lead-acid and lithium-ion batteries in a hybrid storage device. A model is presented for calculating the electrical characteristics of these units during operation. The possibility of choosing a hybrid drive structure that provides a comparable operating voltage range of the units (operation without voltage converters) is demonstrated. The modes of operation of a hybrid energy storage system are modeled both for simple parallel connection and for switching blocks according to a threshold algorithm. It is demonstrated that in order to equalize the discharge rate of the main and additional units, it is necessary to coordinate the capacity of the ESS, the degree of hybridization, the type of load and the electrical parameters of the batteries, which is impossible without modeling the system. When the threshold switching of the blocks takes place, additional control parameters, making it possible to change the discharge rate of the additional block and increase the economic efficiency of the hybrid ESS. Estimates of the economic efficiency of hybrid ESSs have been made for different values of the threshold switching voltage of the lithium-ion unit, as well as for three characteristic loads: an electric forklift truck, a 30-apartment apartment building and a 300-apartment residential complex. The results demonstrate the features and technical and economic potential of passive hybridization, can be used for the design of hybrid ESSs for small power systems with solar and wind power plants, in the calculation and design of generator – storage – consumer systems.

The paper presents the results of a study to determine the rational structure of mini-CHP (Cogeneration Heat and Power Plant) using local fuels types (LFT) for operation as part of the United Energy System (UES) of Belarus with a surplus of electricity generating capacity and dominance of imported types of energy resources (natural gas and nuclear fuel) in the fuel balance. When optimizing the operating modes of mini-CHPs using LFT and operating in parallel with the UES, which has a significant surplus of electricity generating capacity, it is necessary to separate options for existing stations and options for newly built ones. In the first case, due to the fact that the power of the equipment is known, it is advisable to consider two extreme options, i.e., the operation of the heating unit according to an electrical or thermal load schedule. In this case, in order to maintain the daily consumption traffic it is necessary to provide for the accumulation of thermal or electrical energy, respectively. In the case of new construction, the optimized parameter is the power of the generating equipment, so it is advisable to give preference to the option with the maximum number of hours of use of the rated power. In order to increase the economic attractiveness of mini-CHP, options for developing the structure of mini-CHP using LFT with the transition to multi-generation technologies and adaptation to the existing operating conditions of the UES of Belarus have been considered. The results of an analysis of commercially available technologies for storing excess electrical energy are presented in accordance with current and projected (until 2030) cost and operational indicators. For adapting mini-CHP to operate in the UES in conditions of a surplus of electrical power capacity, an electrical energy storage system using hydrogen as an intermediate energy carrier is of greatest interest. To utilize the excess electrical energy consumption from a mini-CHP with a heating ORC unit during the daily dips, a structural diagram configuration using an alkaline electrolysis module for hydrogen production is proposed. The efficiency of energy storage and use technology is considered depending on the specific energy intensity for various electrical energy storage technologies. The use of the two most energy-intensive energy storage technologies is proposed: accumulation based on electrochemical batte-ries and the “electricity-hydrogen” type. During the study, an analysis of the functioning of the ORC-installation Turboden 14 CHP ORC-installation operating as part of a mini-CHP using LFT was carried out. It was revealed that today the installation operates in a wide range of load changes (from 17 to 87 % of the rated electrical power), while the generation of electrical energy from thermal consumption varied in the range from 0.20 to 0.026 MW/MW. Due to the fact that the ORC installation under study is a component of the energy source with a high installed peak thermal power, in the current state there is no direct correlation between the outside air temperature and the generation power of the ORC installation. This circumstance indicates the need to continue the study of heat load trends to build functional models for short- and medium-term forecasting of heat load depending on the time of day and average hourly outside air temperature, which was implemented in the second part of the work.

Steel underground gas pipelines occupy a significant share of the total length of gas distribution pipelines, and therefore their maintenance in proper condition is a constant and very urgent task. Due to its global nature, the main influencing factor affecting the technical condition of any steel underground pipelines, including gas pipelines, is corrosion, primarily soil corrosion. To protect against it on pipeline networks, along with insulating coatings, electrochemical protection (ECP) is applied, that is, following the definition of STO [Standard of Organization] 17330282.27.060.001–2008, protection of metal against corrosion in an electrolytic environment, carried out by establishing a protective potential on it or eliminating the anodic potential shift from the stationary potential. In the gas distribution industry of the country, methods and means of electrochemical protection have been applied since the beginning of gasification and the construction of the first gas pipelines. All gas supplying organizations of the State Production Association for Fuel and Gasification “Beltopgaz” (six regional and Minsk city), which operate gas distribution facilities, have specialized corrosion protection services. These services provide maintenance of available ECP equipment, conduct electrical measurements on gas pipelines and corrosion studies of soils, and have certified laboratories. This paper is devoted to the analysis of domestic experience in organizing electrochemical protection of steel underground gas distribution pipelines, searching for promising directions for its improvement and increasing efficiency through the implementation of a unified industry technical policy, automation and telemechanization of ECP equipment in the general context of digital transformation, optimization of the timing and volume of maintenance.

Incompliance of the settings of the system to control actual values of the parameters of a variable frequency induction electric drive may sometimes result in complete non-operability of a variable frequency electric drive as well as in the considerable reduction of the dynamic quality parameters. Such parameters as active rotor resistance, rotor inductance, and inductance of the magnetization circuit are available for the immediate measuring. They are not identified in terms of the acceptance tests, and the values presented in catalogues and reference books are calculated ones that may differ considerably from the real values of a certain machine. Despite constant studies by the researchers, a task to identify electromagnetic parameters of the equivalent circuit of an induction motor is still important and topical. The objective of the paper is to develop a method of online-identification of the electromagnetic parameters of an induction motor making it possible to implement accurate regulator adjustment of the frequency control system in terms of operational changes in the driving motor parameters. For the first time, the paper analyzes a steady mode of induction motor operation which does not apply T-network of the equivalent circuit of an induction motor. An approach has been proposed relying on the equation of an induction motor in three-phase fixed coordinate system obtained on the basis of the theory of generalized electromechanical converter.

In this article, the authors consider the possibility of using a hybrid energy storage system to even out the load profile of the enterprise. Solving the problem of rational use of energy storage taking into account the initial variable load schedule will significantly reduce not only the cost of electricity consumption by the enterprise, but also the costs of its production. Detailed characteristics of batteries with various types of electrolytes and supercapacitors are given. A model of the active scheme of a hybrid electric energy storage system consisting of a lithium-ion battery and a supercapacitor unit with the corresponding characteristics is presented. The model was carried out by using the SimPowerSystems software in MatLab. During the simulation, the temperature and the aging effects and of the batteries were not taken into account. The selfdischarge parameter of the battery was also not presented. As a result of the simulation, discharge characteristics of supercapacitors and batteries were obtained based upon which the expediency of their combined use for leveling load profiles of various types was substantiated. The paper presents the results of the simulation of operating modes of a hybrid energy storage device, combining the advantages of two types of energy storage devices, as well as a diagram of delivered power to the network, corresponding to the specified parameters. The paper provides a mathematical description of the increasing power by hybrid storage system resulting from the combined use of supercapacitors and batteries. The paper presents the dependence of the power increase ratio on the frequency and the pulse current duty ratio, which proves that the maximum possible output power of the hybrid storage system can be several times greater than the power of a single battery having the same parameters.

In the first part of the paper the theory of infrared radiation and the use of nondestructive measurement of electrical devices by means of thermovision are under analysis. In the second part of paper basic principles and application of non-contact temperature measurement are examined. In the third part of paper thermal processes in distribution oil transformer – temperature in dependence on height of oil transformer and temperature distribution in sectional plan of oil transformer – are considered. In the fourth part of paper, by means of the experimental measurements and subsequent analysis, practical thermal imaging and contact thermal measurements by optical detectors for the diagnosis of distribution oil transformers in the field of mechanical strength of windings are shown. In this paper, we wanted to show out the possibility of using thermal measurements in this field of analysis and detection of quality of winding for distribution oil transformer. It is possible to use these methods to localize places of faults, and they are also applicable for the diagnosis and detection of disorders of the quality of materials and other anomalies during operation of the equipment. By means of the experimental measurements followed by diagnostic analysis the practical use of thermovision and optical sensors for diagnostics of power oil transformers in field mechanical strength and quality of winding is demonstrated.

The paper presents a fragment of on-going investigations directed on creation of optimal information environment that ensures an access to the R&D publications from the known scientific journals and other scientific serials which are necessary for qualitative execution of scientific and technological activities on priority areas in highway engineering. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific publications which are necessary for execution of investigations on heat and mass transfer in road dressings. Their deformations occur under various climatic conditions due to heat and mass transfer processes, interaction of transport flows and road surface that leads to crack formation in depth and on the surface of road dressings. Structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-, reinforced concrete, concrete, brick scrap and products of their recycling, various wastes of production etc.) exerts an influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to viscosity, air velocity, geometric characteristics, permeability, capillary pressures in materials. It has been shown that calculations based on principles of complex number usage have specific features in engineering practice: it is required to observe their accuracy in approaches, calculation reduction due to some accuracy degradation as a consequence of transition from complex numbers to their modules with exclusion of phase shift account and related with propagation of thermal waves. In this respect calculations of heat resistance without phase shifts are considered as rather important if they are in agreement with principles based on the fact that a complexity is characterized by thermal absorptivity of the material in a great number of calculations. The investigations have been supported by Henan Center for Outstanding Overseas Scientists, Grant Number GZS 2018006 (People’s Republic of China, Henan Province).

The paper presents a fragment of on-going investigations directed on creation of optimum data environment that ensures an access to world scientific journals and other publications which are necessary for qualitative implementation of works on priority directions of R&D in the field of road-construction industry in the period of 2016–2020. A citation analysis has been applied while using data of Journal Citation Reports for selection of world scientific serial publiccations which are necessary for execution of investigations on heat and mass transfer in road dressings. The road dressings are considered as open heterogeneous thermodynamic systems. Their deformations occur under various climatic conditions due to heat and mass transfer processes and interaction of transport flows and road surface. Crack formation takes place in depth of the road dressings and on road surfaces as a result of temperature, mass transfer processes. As it is known material structure of constructive layers especially which are created with the help of technogenic wastes (asphalt-concrete, concrete, reinforced concrete scrap and products of its recycling, brick rubble, various wastes of production etc.) influence on heat and mass transfer. The paper presents results of investigations on heat flows, boundary layers according to air viscosity, velocity of geometric permeability characteristics, capillary pressures in road pavements.

. It is a very challenging task to correctly use weather data to calculate the active power loss due to corona in overhead power lines. One of the significant reasons for this was the problem of accuracy of determining weather conditions and the use of the forecast for calculating extended overhead lines. In the USSR (Union of Soviet Socialist Republics), based on field tests and experimental data, recommendations were developed for accounting for losses of electric energy due to corona and interference in overhead lines, the average values of which were given in the relevant instruction for the regulation and justification of the norm of electricity consumption for its transmission over electric networks. According to this regulatory document, the specific cost of active power due to corona in overhead lines, averaged by design, was determined depending on weather conditions, which were divided into four groups. In this paper, the effect of active power losses on corona is estimated using various factors on the example of high-voltage overhead lines in the main electrical networks of the Republic of Belarus of various rated voltages. Dependences of active power losses due to corona have been constructed and modeled, taking into account different climatic and weather conditions observed in the country. The determination of metrological parameters was based on the analysis of weather data and patterns of types of weather conditions. In order to improve the accuracy of calculating the specific losses of active power due to corona, all possible weather conditions were considered, as well as their combinations. Afterwards, the data on weather conditions were processed and their types were reduced to one of the four existing types of weather. A method for determining electric power losses due to corona in overhead lines based on the average relative air density and geometric parameters of the predominant section of overhead lines has been proposed and presented. It is shown that the usage of exclusively rated voltage can cause errors in determining both the specific and actual values of active power losses for corona.

The paper discusses the circumstances and technical solutions that contribute to the integration of electrical and thermal networks of urban neighborhoods within the framework of a surplus of electricity generating capacities arising from the imbalance in the development of energy generation and consumption, stochastic processes of market economy development, the transfer of energy-intensive industrial production to other countries, the desire to diversify fuel energy resources, passion for the construction of energy sources for alternative energy resources in counterbalance to traditional energy facilities without taking into account all aspects of the interaction of the former with the environment, etc. With regard to district heating systems of electrical and thermal networks of urban neighborhoods, the use of hybrid heating points is achieved, which, unlike standard solutions, are equipped with electric boilers, thermal accumulators and heat pumps. According to the time of use of generating capacities, preference should be given to options for covering the hot-water load. Based on the average daily load, the power usage time in this case lies in the range of 6000–6500 hours / year. When choosing the capacity of the equipment, it should be borne in mind that the daily load of hot water supply is extremely uneven and also depends on the day of the week, while the maximum load exceeds the average daily by 2.5 – 3.0 times. When integrating electricity and heat supply systems, it is advisable to consider options for only night-time electricity consumption or night-time consumption plus consumption during the hours of daytime failures of the electricity consumption schedule. If during the new construction the power of the electrical network may vary depending on the selected option, then during the modernization of the heat supply system, the problem is solved if there is a limitation on the available electrical power. Therefore, the definition of these restrictions is a separate issue. In comparison with the direct consumption of electricity for the needs of heat supply, which is a priori energetically and economically inefficient, the use of hybrid systems in heat supply allows us to solve the multifunctional task of increasing the reliability of energy supply and the stability of the functioning of the power system, which is primarily achieved by solving the problem of balancing the capacity of production and energy consumption from the position of aligning schedules of energy generation and consumption.

The output of power unit No 2 of the Belarusian NPP to the level of neutron power development of 100 % of the nominal level has changed the structure of generation of the Unified Energy System (UES) of Belarus. At the current loads of the inter-heating period of 2023, the share of a nuclear power plant with two power units operating at full capacity in the daily generation structure of the Republic is about 50 %. In order to balance the UES of Belarus during the operation of two power units of a nuclear power plant at night, the application of adjustment regulatory measures that exceed the available capabilities is required. The almost complete use of the adjusting range of the CHP will forcibly cause, on a larger scale, to the shutdown of the blocks during the load failures at night, followed by the start-up from the non-cooled and hot statuses. These operating modes of generating equipment are inevitable in the current conditions of the electricity market, which has led to the emergence of most complex tasks to assess the economic and technical efficiency of involving or another equipment of power plants in such modes. The paper proposes an approach to solving the problem of achieving an effective combination of reliability and efficiency of energy systems on the example of gas turbines and CCGT power units. A generalized desirability function has been obtained, which includes a number of parameters for choosing a rational relationship and mutual influence between the reliability and efficiency of electricity production with the participation of thermal power plant equipment in regulating the daily load schedule. The proposed mathematical model is an effective means of analyzing the suitability of equipment for use in the required operating modes.

At industrial CHP plants which are characterized, in particular, by steam supply to industrial consumers, in cases with significant condensate losses, it is proposed to develop a system of feed water regenerative heating by utilizing low-temperature waste heat flows those are available directly at the CHP plant. The regenerative use of low-temperature heat flows within the CHP that is proposed is possible only on the basis of heat pumps use. In this context, the use of electrically-driven heat pumps (EHP) and absorption heat pumps (AHP) is considered. It is shown that, despite the higher heating coefficient of the EHP, the thermodynamic (exergetic) efficiency and economic efficiency of the AHP are higher. Furthermore, the latter also has operational advantages. It is possible to use heat flows with various heat carriers as AHP drive, those are required for the transfer of thermal energy from a cold source to a hot receiver. In this paper, using the example of the “PT-60” steam turbogenerator unit, which is the most common type for CHP plants of the Belarusian power system, the indicators of the primary fuel use efficiency growth at the CHP plant for the AHP with a steam drive are determined. Three scenarios of the use of AHP as part of the thermal scheme of the CHP are considered, viz. with an increase in generation, with the maintenance of generation or with a decrease in the generation of electric energy. The latter is relevant in the current situation with the Unified Energy System of Belarus. In this case, while maintaining the minimum steam flow into the condenser of 12 t/h, the following increase in the plant efficiency has been obtained: electrical efficiency increased by 0.90 %, energy efficiency – by 0.55 %, and exergetic efficiency – by 0.23 %.

Renewable energy sources (RES) are seen as a means of the fuel and energy complex carbon footprint reduction but the stochastic nature of generation complicates RES integration with electric power systems. Therefore, it is necessary to develop and improve methods for forecasting of the power plants generation using the energy of the sun, wind and water flows. One of the ways to improve the accuracy of forecast models is a deep analysis of meteorological conditions as the main factor affecting the power generation. In this paper, a method for adapting of forecast models to the meteorological conditions of photovoltaic stations operation based on machine learning algorithms was proposed and studied. In this case, unsupervised learning is first performed using the k-means method to form clusters. For this, it is also proposed to use studied the feature space dimensionality reduction algorithm to visualize and estimate the clustering accuracy. Then, for each cluster, its own machine learning model was trained for generation forecasting and the k-nearest neighbours algorithm was built to attribute the current conditions at the model operation stage to one of the formed clusters. The study was conducted on hourly meteorological data for the period from 1985 to 2021. A feature of the approach is the clustering of weather conditions on hourly rather than daily intervals. As a result, the mean absolute percentage error of forecasting is reduced significantly, depending on the prediction model used. For the best case, the error in forecasting of a photovoltaic plant generation an hour ahead was 9 %.

The paper considers modern approaches to usage of hydrocarbon-containing waste as energy resources and presents description of investigations, statistic materials, analysis results on formation of hydrocarbon-containing waste in the Republic of Belarus. Main problems pertaining to usage of waste as a fuel and technologies for their application have been given in the paper. The paper describes main results of the investigations and a method for efficient application of viscous hydrocarbon-containing waste as an energy-packed component and a binding material while producing a solid fuel. A technological scheme, a prototype industrial unit which are necessary to realize a method for obtaining multi-component solid fuel are represented in the paper. A paper also provides a model of technological process with efficient sequence of technological operations and parameters of optimum component composition. Main factors exerting significant structure-formation influence in creation of structural composition of multi-component solid fuel have been presented in the paper. The paper gives a graphical representation of the principle for selection of mixture particles of various coarseness to form a solid fuel while using a briquetting method and comprising viscous hydrocarbon-containing waste. A dependence of dimensionless concentration g of emissions into atmosphere during burning of two-component solid fuel has been described in the paper. The paper analyzes an influence of the developed methodology for emission calculation of multi-component solid fuels and reveals a possibility to optimize the component composition in accordance with ecological function and individual peculiar features of fuel-burning equipment. Special features concerning storage and transportation, advantages and disadvantages, comparative characteristics, practical applicability of the developed multi-component solid fuel have been considered and presented in the paper. The paper cites practical results pertaining to usage of hydrocarboncontaining waste for the equipment applied for production of multi-component solid fuel. Data on economic expediency for usage of the multi-component solid fuel with high thermo-technical characteristics in the boiler-houses operating on local solid fuel have been analyzed in the paper. The paper shows a perspective evaluation, applicability and practical significance of the solution of the problem on efficient usage of hydrocarbon-containing waste while producing the multi-component solid fuel.

The article considers experimental and analytical determination of the asynchronous machine equivalent-circuit parameters with application of the reference data. Transient processes investigation of the asynchronous machines necessitates the equivalent circuit parameters (resistance impedance, inductances and coefficient of the stator-rotor contours mutual inductance) that help form the transitory-process mathematical simulation model. The reference books do not provide those parameters; they instead give the rated ones (active power, voltage, slide, coefficient of performance and capacity coefficient) as well as the ratio of starting and nominal currents and torques. The noted studies on the asynchronous machine equivalent-circuits parametrization fail to solve the problems ad finem or solve them with admissions. The paper presents experimental and analytical determinations of the asynchronous machine equivalent-circuit parameters: the experimental one based on the results of two measurements and the analytical one where the problem boils down to solving a system of nonlineal algebraic equations. The authors investigate the equivalent asynchronous machine input-resistance properties and adduce the dependence curvatures of the input-resistances on the slide. They present a symbolic model for analytical parameterization of the asynchronous machine equivalent-circuit that represents a system of nonlineal equations and requires one of the rotor-parameters arbitrary assignment. The article demonstrates that for the asynchronous machine equivalent-circuit experimental parameterization the measures are to be conducted of the stator-circuit voltage, current and active power with two different slides and arbitrary assignment of one of the rotor parameters. The paper substantiates the fact that additional measurement does not discard the rotor-parameter choice arbitrariness. The authors establish that in motoring mode there is a critical slide by which the stator current value turns out to be the minimum.

Increasing the solid lighting facilities operational energy-efficiency in the national economy of the Republic of Belarus is of current concern. The modern problems of energy-saving lighting are multifaceted and broad-ranging. It is particularly burning amidst the energy crisis and the world commercial slump. Thus, the lighting demands 10–13 % of the total electric energy consumption in Belarus. That is to say, there is a significant potential of energy saving in transition to energy-efficient lighting. The paper considers the issues of reliability and service period of the solid-state lighting devices created on the basis of lines of light-emitting-diodes (LED) produced by Paragon Semiconductor Lighting Technology Co., Ltd. The optoelectronic apparatuses reliability assessment is based on investigation of the development principles and deterioration mechanisms leading to failures of one kind or another. The deterioration causes ascertainment is indispensable for acting upon them later on and thus reducing the degradation speed and extent. One of the LED-devices deterioration main sources is the temperature overheat of the LED-chip active area. Therefore, techniques for evaluating the heat characteristics of solid lighting devices become the issue of the day. The article investigates thermal properties of high-capacity blue LED-lines by method of electrical transient processes. The authors calculate temperatures in the LED-lines active areas at various heat-dissipation conditions and injection currents values. They realize computer generated simulation of the heated lines thermal fields applying the ANSYS packet. The study concludes that out of the degree of temperature-distribution heterogeneity along the line impossibility of the line chip structural units thermal characteristics extraction arises based on all LEDs homogenized over the line temperature-time dependences. The paper indicates that one can with reasonable accuracy obtain the LED-lines thermal parameters employing the line representation with two equivalent RC-strings corresponding the thermal ways ‘LED active area – aluminium base’ and ‘aluminium base – environment’. For these areas thermal time constants, thermal resistances and thermal capacities are determined.

The energy system is a structure that is among the most complex artificial objects, the successful functioning and development of which is absolutely necessary to ensure the livelihoods of a modern state. In this regard, its continuous monitoring with obtaining reliable and objective performance indicators is undoubtedly in demand. Traditional key energy indicators (specific consumption of conventional fuel for electricity generation and heat release) do not give a complete picture of the operation of the power system for such complex structures and in some cases are calculated incorrectly. The present paper proposes to add a well-known, but practically unused exergetic efficiency coefficient to the range of traditional characteristics. Its application expands the monitoring capabilities and increases the objectivity of the evaluation. For the first time, the analysis of various periods (annual, heating and inter-heating) was carried out on the example of thermal power plants (CHP) of the Unified Energy System of Belarus. The relative power generation of the CHP before the commissioning of the Belarusian NPP was estimated at ≈45 %, and after commissioning it decreased to ≈39 %. More than half of the annual consumption of thermal energy in Belarus is accounted for by heat-generating sources, while thermal power plants provide up to 88 % of heat output. The installed electric capacity utilization factor, the extraction factor and the average annual specific generation of electricity on thermal consumption for each CHP separately have been determined. The results are presented graphically, which makes the content more informative and facilitates the perception. Solutions have been proposed to improve the efficiency of the CHP.

Employing dolomite in the capacity of a sorbent for generator gas purification is of considerable interest nowadays, as it is the impurity of generator gas that causes the major problem for creating cheep and effective co-generator plants. Designing gas purification systems employs simple but physically adequate macrokinetic models of dolomite thermal decomposition. The paper analyzes peculiarities of several contemporaneous models of dolomite and calcite thermal decomposition and infers on reasonable practicality for creating compact engineering dolomite-decomposition macrokinetic models and universal techniques of these models parameter reconstruction for specific dolomite samples. Such technics can be founded on thermogravimetric data and standard approximation error minimizing algorithms.The author assumes that CO2 evacuation from the reaction zone within the particle may proceed by diffusion mechanism and/or by the Darcy filtration and indicates that functional dependence of the thermal-decomposition rate from the particle sizes and the temperature differs for the specified mechanisms. The paper formulates four macrokinetic models whose correspondence verification is grounded on the experimental data. The author concludes that further work in this direction should proceed with the dolomite samples investigation and selecting the best approximation model describing experimental data in wide range of temperatures, warming up rates and the particle sizes.

The paper considers the issue of one of the widespread types of vector control realization for the asynchronous motors with a short-circuited rotor. Of all more than 20 vector control types known presently, the following are applied most frequently: direct vector control with velocity pickup (VP), direct vector control without VP, indirect vector control with VP and indirect vector control without VP. Despite the fact that the asynchronous-motor indirect vector control without VP is the easiest and most spread, the absence of VP does not allow controlling the motor electromagnetic torque at zero velocity. This is the reason why for electric motor drives of such requirements they utilize the vector control with a velocity transducer. The systems of widest dissemination became the direct and indirect vector control systems with X-axis alignment of the synchronously rotating x–y-coordinate frame along the rotor flux-linkage vector inasmuch as this provides the simplest correlations for controlling variables. Although these two types of vector control are well presented in literature, a number of issues concerning their realization and practical application require further elaboration. These include: the block schemes adequate representation as consisted with the modern realization of vector control and clarification of the analytical expressions for evaluating the regulator parameters.The authors present a technique for evaluating the dynamics of an asynchronous electric motor drive with direct vector control and x-axis alignment along the vector of rotor flux linkage. The article offers a generalized structure of this vector control type with detailed description of its principal blocks: controlling system, frequency converter, and the asynchronous motor.The paper presents a direct vector control simulating model developed in the MatLab environment on the grounds of this structure. The authors illustrate the described technique with the results of the computer based simulation of a specific electric drive on the basis of an asynchronous motor 4А132S4У3 (7,5 kW) with direct vector control at the rated loading. The results confirm validity of the presented technique to investigation of the

The paper considers one of the ways for improving power quality videlicet employment of the power active filtering-balancing devices capable of contemporaneous exercising compensation of the reactive power consumed from the mains, distortion power, and symmetrizing the phase currents with high precision and operating speed. In forming the current of the power active filtering-balancing device a few power theories gained ground, distinguishing among others the Frieze theory and the p–q theory. These presentations differ from the methods laid as theoretical grounds of the electric energy accounting systems.The article presents an analysis in the compliant system of the effect of the current projections on the power components formation character. The authors formulate the advantages and defective features of the noted theories being applied in case of the power active filteringbalancing device operating with unsymmetrical parameters of the mains. The paper considers the vectors asymmetrical system presentation by means of the symmetrical components 1–2–0 (Fortescue transformation) and in via α–β–0 re-expression (Clarke transformation). For practical evaluation of the currents correlation in α–β–0 and 1–2–0 measuring systems, the authors stage and perform a series of experiments where oneand two-phase amplitude asymmetries, one-phase phasic dissymmetry as well as asymmetries with occurrence of higher harmonic components are realized. The currents effective values summary from the series of experiments being presented graphically as function of the unsymmetry current amplitude educe incongruity of the results. Visually however, a similarity of the form and the character is observed, which allows performing correlation coefficient estimation of the mean square values of the currents in α–β–0 and 1–2–0 systems. That allows making conclusion of a high degree of the obtained results correlation.

The author represents the method of creating composite 3D-models employing technology of geographical information systems for environmental impact assessment of projected, constructed and operating energy facilities. The paper describes the techniques of applying bundled software ArcView with add-on modules ImageWarp and RASTRProfi for alignment of multiscale bit-mapped and direct-beam three-dimensional models with the object of evaluating ecological risks for diverse territories.The article evaluates the environmental impact of a thermal power plant near the city of Rasht (industrial area Saravan) and demonstrates analysis of the territorial distribution of the soil contamination with varied pollutants at different wind structures. The paper demonstrates the method of building composite 3D-models applied for assessment of presumable incidents with radioactivity discharge at the nuclear power plant in Halileh, 20 km from the city of Bushehr. By analyzing the wind diagram in the territory being explored and determining the predominant wind directions in different periods, it is possible by way of employing this method to distinguish the territories and the objects with most unfavorable prognosis. This enables rendering a prompt decision on the measures minimizing unfavorable impact on the population and environment.Altering the point of topographical survey while synchronizing the scales, the researcher can place the designed project within any territory and analyze the necessary parameters for each variant.The author considers the presented in such a manner technique worth productive implementing while analyzing environmental impact of both operating and projected industrial facilities (industrial and agricultural enterprises, thermal and nuclear electric-power plants etc.).

The paper demonstrates the fact that in valuating the actual heat efficiency from utilizing the vortical heat-release intensification it is necessary to account for the increase of heatreleasing area of the tube with the corresponding lacunae (hollows, lunules). It may vary from 4 to 280 % as a function of their geometrical parameters which causes heat-release increasing with its simultaneous growth from vortex formation in the boundary-layer flow by the swirls generated by lunule turbulizers. For the tube of axial flow-around with hollows applied on the outer surface the vortex intensification enhances the thermal effectiveness up to 1,39 times, and in the case of the transversal flow-around tube banks with lunuled tube outer surface it does not exceed 29 % at Re = 5000. With Re number growing to 14000 the energy effect tangibly declines to 6 %.The thermal effectiveness of the vortex intensification with spherical lunules on the tube inside surface and the air moving inside does not exceed 13 % in the interval Re = (1−2) ⋅ 104 , which is distinctive for air the preheaters of steam-boilers. However, a greater energy effect (up to 33 %) for the axial flowing is attained from emerging saliences on the tube inside surface beneath the spherical lacunae on the outside. The authors establish that employing discrete roughness in the form of transverse circular saliences (diaphragms) allows attaining much greater heat-emission intensification (up to 70 %) in the interval of Re = (10−100) ⋅ 103 as compared to the smooth tube. The paper shows that physical principles of the heat-emission vortex intensification by way of lunuling the round tubular surfaces differentiate from those applying artificial limited roughness in the form of pyramid frusta on the tube outside surfaces flowed around by the transverse flow.