RELEVANCE of the research is in the development of a non-destructive method for diagnosing porcelain insulators of high-voltage electrical equipment based on analysis of the characteristics of partial discharges (PDs). The problem of the final stage of breakdown of both the discharge gap and porcelain insulators recognizing is currently has not solved. THE PURPOSE. Recognition of PDs in solid insulation, study of PDs characteristics in a pre- breakdown situation, recognition of defective insulators based on PDs characteristics analysing. METHODS. The study of PDs characteristics for a defective and functional porcelain insulator were carried out. To study the characteristics of various types of PDs, including in the pre-breakdown situation, a system of surface-needle electrode system was used. RESULTS. The article describes compares the PDs characteristics obtained using standard R-400 device and a digital storage oscilloscope (DSO) using a telescopic antenna. A technique for recognizing the development of the pre-breakdown situation of the surface-needle discharge gap and the porcelain insulator was developed. The technique for recognizing a defective porcelain insulator from the amplitude-phase diagrams (APD) of PDs was developed. The method for assessing the breakdown voltage of porcelain insulators based on the characteristics of partial discharges was developed. CONCLUSION. At the moment of transition to the pre-breakdown stage were observed a sharp increase in the counter-movement of charges of opposite polarity. In the stage immediately before the breakdown, near zero values of the applied voltage of negative polarity, ordered PDs of the same polarity as the applied voltage were recorded in large numbers. These discharges led to an increase in leakage current and were interpreted as initial corona discharges. These discharges were recorded both by a telescopic antenna in a surface-needle system and in porcelain insulators.

RELEVANCE. The current technical condition of electrical networks at the moment is generally unsatisfactory with an average level of physical wear of about 60-70 %, therefore,the development of fundamentally new methods for assessing their technical condition is currently an urgent task. The methods of assessing the technical condition of electrical networks analyzed in the article are based to a greater extent on the subjective and insufficiently accurate method of expert assessments, which actually does not take into account the data of its technical diagnostics, as well as statistics of defects and failures. OBJECT. To develop a methodology for assessing the technical condition of electrical networks, which would be based on probabilistic models characterizing the physical processes occurring in electrical networks, as well as data from their technical diagnostics, statistics of defects and failures. METHODS. To assess the technical condition of electrical networks, a probabilistic assessment method was used. In this case, the methodology involves sequential determination of the probabilities of occurrence of selected groups of emergency modes, the probability of failure of a network element as a whole, as well as the probability of failure of an object and a group of objects of the power grid. RESULTS. Based on the research results, probabilistic models of failure of electrical networks were obtained, which, unlike the assessment methods discussed in the article, are based on data from technical diagnostics and inspections of electrical equipment. An example of the implementation of the developed methodology on real electrical network objects is given. CONCLUSION. The developed methodology allows for a more reasonable prioritization of technical impacts on electrical grid equipment, which will make it possible to replace or repair equipment that has actually exhausted its physical resource, which will reduce the frequency of emergency conditions and reduce damage from power supply interruptions.

RELEVANCE of this study lies in the use of an artificial neural network to predict the volume of water in the Coca reservoir (Coca hydroelectric power station in Ethiopia). As you know, hydropower, being renewable energy, is one of the technologies that produce electricity with the least impact on global climate change. During this time, Ethiopia received about 87% (4,674 MW) of electricity from hydropower. It is one of the countries affected by the problems of climatic phenomena, such as floods, droughts and hurricanes, which affect the potential of hydropower. THE PURPOSE. In order to maintain safe operation, good production efficiency, better water resources management, effective decision-making, accident prevention and early warning and restrictions on electricity production, water volume forecasting is necessary. Which, in turn, is a nonlinear problem, and a multilinear perceptron-type neural network (MLP) is suitable for this purpose. METHODS. In this study, different models with different selected number of nodes and layers were identified, since there is no specific rule for determining the architecture of an artificial neural network. Statistical analysis (mean square error (MSE) and R-squared (R2)) was used to verify the validity of the model by comparing the actual values of water inflow with the predicted values. results. The inflow prediction was carried out using the ANN method based on a multilayer perceptron (MLP). The performance of each model was evaluated using the mean square error (MSE) and efficiency coefficient (R2), which are among the most commonly used statistical methods in hydrological modeling. CONCLUSION. The results obtained show that the models successfully predicted flood runoff over the reservoir.

PURPOSE. Modernization of the PGU with an increase in thermal power and preservation of electrical power using a block afterburning device (BDU) in a heat recovery boiler (CU). METHODS. Comparative studies of the characteristics of the PGU-450 without a BDU and with an installed DBU were conducted results. As a result of comparative studies of the main characteristics of the PGU-450 and the main characteristics of the PGU-450 before and after installation of the DBU in recovery boilers, it was shown that the use of the BDU effectively solves the problem of covering peak thermal loads in the transition periods of the OSP (spring – summer; autumn – winter); the possibility of long-term operation of the BDU during the entire period of operation of the PG unit is shown; it is revealed that it is most advisable to implement the BDU on the PGU blocks for which the obligations under the DPM agreements have expired. By increasing the electric power by 6% (in the heating mode), the payment for power in the KOM market increases; an increase in the electric power of the PGU unit when operating in condensation mode by 11% minimizes the under-supply of power to the OREM at outdoor temperatures above + 15 degrees; Despite a 3% increase in URUE to 190 g/kWh, the electric energy produced remains competitive in the OREM. CONCLUSION. Thus, as a result of the research, it was shown that when the DBU is switched on, the thermal power of the PGU-450 increases to 320 Gcal/hour, which makes it possible to cover the missing thermal power. Thus, the operation of the T-250 in a mode close to condensation with an URUT ee of 350 g / kWh is excluded, and the entire thermal load is covered by the PGU-450, but with a slightly degraded URUT ee of 190 g / kWh. Such a composition of the CHP equipment ensures the maximum possible economic efficiency of the plant in the electricity market with full coverage of heat consumption.

RELEVANCE: The relevance of this work lies in the study of new porous materials for use in compact, highly efficient heat exchange devices. PURPOSE: To investigate the hydro-aerodynamic properties of flows passing through porous inserts based on triply periodic minimal surface (TPMS) topologies. To develop a methodology for studying porous materials with ordered structures. To identify potentially suitable TPMS-based porous materials for application in heat exchange equipment. METHODS: Numerical (CFD) and experimental methods were used to address the research objectives. Ansys Fluent 2019 R3 software was utilized for numerical modeling. Experimental samples for the physical experiments conducted on the VENT-08-7LR-01 laboratory setup were fabricated using SLA additive technologies. The porosity of the samples ranged from 0.73 to 0.89. The experiment was conducted with inlet velocities ranging from 0.3 to 4.5 m/s. RESULTS: New empirical dependencies of pressure drop on flow velocity were obtained for inserts based on the surfaces: Primitive (P), Fischer Koch S (FKS), Neovius (N), and Schoen's I-WP (IWP). The airflow through the N structure showed the highest pressure drop, while the P structure had 8 times less pressure drop at the same velocity. Stagnation zones, which can negatively impact heat transfer, were identified in the porous inserts. Changes in local flow velocity in the porous inserts were determined to correlate with the insert's transparency. CONCLUSION: The research results can be used for designing cooling systems with TPMS-based ribbing. Based on the analysis of the velocity vector field distribution and pressure drops, the FKS and IWP structures have potential applications in heat exchange equipment.

RELEVANCE of the study lies in the development of an algorithm for controlling a DC voltage converter capable of providing a high-quality transient process with a wide change in the input parameters of the control object, affecting its nonlinear properties. purpose. THE PURPOSE. To consider methods for the development of continuous and discrete control systems for a step-up DC voltage converter and to obtain an analytical dependence of accounting for the nonlinear properties of the converter that affect the quality of regulation of the output voltage of the voltage stabilizer METHODS. The method of the average geometric root was chosen as a method for calculating the coefficients of the DC voltage converter control system, and the current circuit is adjusted using the technical optimum method, and the voltage circuit using the symmetric optimum method. The obtained analytical solutions of mathematical models and simulation models were compared in the SimInTech software environment. results. RESULTS. The simulation results show that the analytical solution of the mathematical model of the voltage stabilization system has a shorter transition time than the simulation results. This is due to the fact that in the mathematical model according to which the continuous control algorithm was synthesized, the presence of a power input filter, as well as the degree of their precharge, is not taken into account. Because of this, the transition time on simulation models is slower, applied 4 times than in the mathematical model. conclusion. CONCLUSION. When comparing the algorithms with each other, it can be seen that the algorithm obtained by converting a continuous algorithm by the Tusten method has the shortest transition time than all other algorithms. The continuous algorithm and the algorithm obtained by the inverse Euler transformation method have a speed close to each other, and the algorithm obtained by the direct Euler transformation turns out to be the slowest.

THE RELEVANCE of this study lies in solving the problem of reliable functioning of elements of energy systems and ensuring their effective operation during open-pit mining. The paper presents a methodological approach that allows us to assess the level of reliability of low-voltage asynchronous electric motors in a coal mine with complex mining, geological and climatic conditions of production. THE PURPOSE of the work is to quantify the operational factors affecting the service life of an asynchronous electric motor with a short-circuited rotor. Attention is focused on how influencing factors, different in physical basis, among which electrical parameters are highlighted – the coefficient of voltage asymmetry in the reverse sequence, the coefficients of harmonic voltage components and environmental parameters – temperature, air humidity and dustiness, affect the dynamics of changes in the service life of an asynchronous electric motor. Asynchronous electric motors used at one of the enterprises of JSC SUEK in the Trans-Baikal Territory are considered as an object of research. METHODS. The main tool for the implementation of research tasks is computer modeling based on the Matlab software package. RESULTS. The studies were performed on an asynchronous electric motor with a short-circuited rotor with Ph = 3 kW, rated speed 1500 rpm. The simulation of the operating mode of the electric motor under study was performed by changing the experimental parameters: the values of the total coefficient of harmonic voltage components (KU) – from 4 to 12% with a range of 2%; the values of the voltage asymmetry coefficient in the reverse sequence (K2U) – from 0 to 4% with a range of 1%; the ambient temperature (∆Tокr) – from -30°C to +30°C with a range of 10°C; air humidity values (Vc) – 20% and 60%; dust thermal conductivity coefficient values (Kт) – 0,12 and 0,28. Based on the obtained research results, diagrams are constructed that clearly illustrate the dynamics of changes in the service life of an asynchronous electric motor depending on the combination of influencing factors. CONCLUSION. The trends in solving the issues of reliable functioning of a coal mining enterprise with the presence of asynchronous electric motors and ensuring their efficient operation are the most priority, mainly focused on maintaining the stability of technological processes and maintaining the production volumes of a coal mining enterprise. The stability of the electric motor to certain influencing factors is estimated and their critical values are established. Recommendations on the use of asynchronous electric motors are formulated, taking into account their operating conditions.

PURPOSE. The article is devoted to an urgent problem for domestic district heating. A widespread situation is considered when consumers from heat supply systems with a closed connection scheme for hot water supply plants are switched to an open heat supply system from a thermal power plant. METHODS. Study of operating modes of operating heat supply systems was performed. Data collection was carried out using an online system for monitoring and commercial accounting of energy resources. Methodology for calculation of compared mode parameters is proposed. RESULTS. Using the example of the existing heat supply system, it is shown that the effect of the measure to switch subscribers of uneconomical boiler houses to heat sources with combined heat and power generation is leveled by legislative restrictions on the development of open heat supply systems, as well as by the regulatory method for determining heat consumption in hot water supply systems. The main technical and economic indicators were selected for comparative analysis of the operation of the centralized heat supply system in conditions of complete switching of hot water supply plants according to an open circuit and in the presence of a certain number of hot water supply plants with a closed connection scheme. CONCLUSION. The period of inefficient operation of the centralized heat supply system was determined and the amount of annual economic damage was calculated, which made it possible to prove the need to bring all schemes for connecting hot water supply plants in one heat supply system to a single type.

The relevance of the study lies in the consideration and correction of the results of calculations of the single-phase short circuit current in a rural 0.4 kV electric network obtained using existing physical, computer and mathematical methods that give different results. Purpose. Development of correction coefficients for different methods of calculating the single-phase short circuit current in a rural 0.4 kV electrical network. Materials and research methods. During the calculations of the single-phase short circuit current in the 0.4 kV rural electric grid, using different methods, general initial conditions were set: power was supplied from a TM-250 transformer and using A-35 wire. Results. It was revealed that the error between the results obtained using different methods reaches 35.9%. In the work, correction coefficients with values from 0.93 to 1.47 relative units were proposed in order to increase the reliability of calculations. These coefficients made it possible to increase the reliability of the considered methods for determining the current of a single-phase short circuit in a rural 0.4 kV electrical network by 2.9-6.1 times compared with the initial values.

The PURPOSE of the work is to determine the mass-flow characteristics of working substances and energy indicators of an installation based on a CO2 cycle with a two-stage pressure increase (Allam cycle) during oxygen combustion of methanol.METHODS. A research methodology is presented in which the mass-flow characteristics of working substances are determined based on the reactions of combustion and synthesis of methanol and electrolysis of water. These reactions are basic for ensuring operational processes in the installation. The method is based on the molar ratios of substances participating in reactions under stoichiometric conditions. Using the thermodynamic parameters of the cycle being implemented and at a given installation power, the consumption of the working fluid, the share of carbon dioxide renewal in the cycle, the amount of methanol produced in the synthesis unit, the amount of fresh methanol, the amount of hydrogen produced in the water electrolysis unit and the amount of oxygen are determined, necessary to ensure fuel combustion processes. At the same time, the amount of commercial hydrogen is determined. Electricity consumption for own needs is determined using regulatory methods and data from equipment manufacturers.RESULTS. The article shows that with similar values of thermal efficiency of CO2 cycles based on oxygen combustion of methane and methanol, the amount of carbon dioxide removed from the cycle for disposal is 11% less. It has been shown that a CO2 cycle operating on methanol is capable of producing commercial hydrogen simultaneously with electricity generation. The specific electricity consumption for hydrogen production is 22% less than for its production without combination with the CO2 cycle.