Due to the aging and exceeding of the standard service life of steel gas pipelines of the gas distribution system of the Republic of Belarus, it is relevant to study their condition in order to determine the possibility of their further operation. To assess the effects of operating conditions on the level of degradation of the mechanical properties and chemical composition of the metal of steel underground gas lines, a special cycle of studies was conducted within the framework of Beltopgaz State Production Association, including the studies by examining a sampling of gas pipeline specimens in the form of pipe sections extracted from existing facilities of various service life. The analysis of operational factors affecting steel underground gas pipelines is carried out, methods for studying the mechanical properties of metal pipes, microstructure and chemical properties are given. It is demonstrated that the effects of operational loads can result in the following: changes in the geometry of gas pipeline elements; corrosion damage to the pipe wall; formation and development of macrodefects (cracks, delamination, etc.); changes in the mechanical properties and structure of the metal. To assess the state of the microstructure of steel after long-term operation, chemical composition analysis and metallographic studies of the base metal of gas line pipes were also carried out. The chemical composition of the tested specimens was analyzed on an optical emission spectrometer and compared with the permissible ranges of values specified in the standards. It has been established that the metal in areas not subjected to corrosion meets the requirements for steels, and no degradation of its chemical composition and structure has been detected. It has been demonstrated that while the properties of the pipeline’s protective insulation coating are maintained, no signs of aging are apparent in the steel portion of the pipes. Analysis of the test results of the mechanical properties of steel pipes with different service life demonstrated that the operating conditions of the gas distribution system facilities do not result in their degradation. Their mechanical properties, structure, and chemical composition meet the requirements for low-carbon structural steels. It is proved that steel underground gas pipelines with different service life are in satisfactory condition, no degradation of mechanical properties and structure has been revealed.
In accordance with the Concept of the National Strategy for Sustainable Development of the Republic of Belarus for the period up to 2035, the main objective in the gas sector is to maintain production assets at a level that ensures safe energy supply. The basis of these production assets are gas distribution networks, directly gas pipelines. It is known that the factor that poses the greatest threat to the technical condition of steel underground gas distribution pipelines is corrosion. To compensate for the global corrosion factor, steel underground gas pipelines are equipped with special anticorrosive agents, including protective insulating coatings. Bitumen-mastic insulating coatings (BMIC) are the most common coatings in the domestic gas distribution system, which were used earlier than others in industrial practice for corrosion protection. The article provides a comprehensive analysis of BMIC in terms of their design, materials used, and the evolution of coatings from bitumen-mineral to bitumen-rubber and further to bitumen-polymer. A brief overview of the development of theoretical provisions on the structure, physico-chemical properties and component composition of bitumen is presented. The general mechanism of structural degradation of bituminous materials is shown, characterized by a gradual increase in internal stresses, increased viscosity, and brittleness, leading to complete and irreversible destruction. Depending on the temperature conditions and the associated intensity of oxidative processes, autooxidation (low-temperature, low-intensity) and thermal (high-temperature, intensive) oxidation of bitumen hydrocarbon compounds are distinguished. The place of autooxidation and thermal oxidation at the pre-operational (technological) and operational stages of the life cycle of bitumen materials is shown, as well as the influence of temperature effects on the coating material at the technological stage, manifested in an increase in the heterogeneity of the initial state of the coating before its operation.
With the development of technology and population growth, the consumption of energy resources on our planet is increasing. The increasing rate of resource consumption and their irrational use lead to the rapid depletion of fossil fuels. In this regard, a comprehensive study of the efficien-cy of using natural gas at small power facilities in water heating boilers GKS-Dynatherm-3200 and GKS-Dynatherm-1100 was carried out. Industrial and operational tests were fulfilled, heat losses during operation of the equipment and the completeness of natural gas combustion were determined, the composition of the fuel burned was investigated, the concentration, size and shape of solid particles in flue gases were determined using a Zeiss SIGMA VP electron scanning microscope. The test results showed that the burner devices of hot water boilers provide the preparation of a high-quality air-fuel mixture, which makes it possible to organize the combustion process with a minimal excess of air. It was found out that with an increase in the proportion of oxygen in the combustion chamber of the GKS-Dynatherm-1100 boiler to 3.7–5.35 %, an increase in NOx and CO emissions is observed. Despite the high thermal performance, even during the combustion of natural gas in the combustion devices of boiler units, fuel carbon is released in the form of soot. When studying the content of solid particles in exhaust flue gases, it was found that particles with a size from 1 to 5 microns predominate. At the same time, more than 95 % of the particles have a shape close to spherical. Particles of 20 microns or more in the exhaust gases are much smaller, however, their total mass dominates the gross emissions of particulate matter. The emission of particulate matter during operation of the GKS-Dynatherm-3200 water heating boiler with a load of 1.73 MW was 0.17 mg/MJ. During the conducted industrial and operational tests, it was found that the boiler house equipment has high energy-ecological performance and has potential for further improvement.
A rechargeable battery (RB) is a parallel-sequential assembly of cells, the actual capacity and changes of which are specific and determined by the nominal parameters of the cell, the structure of the assembly and the algorithms of the control system (BMS). The article considers the problem of determining the statistical patterns of the actual capacity and its dynamics during cycling for a battery module of the LiFePO4 chemical system with a 16s structure and a parallel pair of such modules. The operation of the corresponding RBs is modeled depending on the initial load variation of the component cells, the balancing characteristics of the latter and other parameters. The effect of disrupting the balancing of sequential assembly cells at a low voltage threshold for the start of balancing has been discovered, and its nature has been explained. Statistical mode- ling of the charging and discharging cycles of battery modules connected in parallel has been carried out. The values of the imbalance of charging and discharging currents of parallel modules and the dispersion of this imbalance are found. Thus, for the considered cell types, there are areas of charge degree (SOC) values in which the charging and discharging currents are compared regardless of the initial imbalance of the cells in the modules. The general trends of reaching the maximum accessible capacity of such systems at different values of the initial cell imbalance are shown. The work is methodical in its nature, and it demonstrates the influence of the statistical variation of cell parameters on the operational parameters of batteries, primarily the accessible operating capacity and the values of the charging and discharging currents of parallel modules. The quantitative results can be used to better understand the processes of balancing and operation of cells in series-parallel assemblies, to optimize BMS operation, and to predict the accessible capacity of lithium-ion cell assemblies.
In digital relay protection systems, the controlled parameters of signals are often their amplitude values. They are usually determined from samples of the orthogonal components of the signals, which are formed by nonecursive digital Fourier filters. At a normal frequency, the amplitude values are determined without additional error. In modes with frequency deviation from the nominal frequency, fluctuations in the received amplitude values occur in the range from minimum to maximum levels. Due to the use of Fourier filters for the formation of orthogonal components, the amplitude determination time is at the level of the power frequency period. The previously developed method of forming the signal amplitude ensures that it does not oscillate at a frequency other than the nominal one. It is based on the use of dynamic cosine and sine of the sampling angle, which are calculated from the instantaneous values of the orthogonal components. When the frequency deviates from the nominal frequency due to the resulting oscillations in the samples of these components, the frequency range of reliable obtaining of dynamic cosine and sine is limited, which causes obstacles to determining the amplitude with an acceptable error. Fast determination of the signal amplitude is achieved through the use of a nonlinear correction factor in the procedure for its formation. However, it is cumbersome to obtain it, taking into account the possible nature of the change in the controlled signal. In this paper, the signal amplitude is determined as the half-sum of the amplitudes of the sine and cosine orthogonal components. At the same time, frequency deviation from the nominal value does not cause significant changes in the magnitude of the controlled amplitude. The use of a transition characteristic for the amplitude of the signal, consisting of sections close to linear, made it possible to simplify the method for determining the mode of signal variation. The conducted computational experiments have confirmed that the developed method for determining the signal amplitude is quite simply implemented at the program level and prevents its oscillations in the frequency range of 45-55 Hz. The proposed technique ensures that the amplitude value of the signal is obtained in less than half of the power frequency period.
One of the main parameters that ensures the standard service life of an electric motor is accordance of the insulation class of the electric motor with its current temperature. Exceeding the temperature above the standard value causes increased resource consumption and premature failure of the electric motor. Therefore, in order to reduce the costs of maintenance, repair and replacement of equipment, it is necessary to control the thermal parameters of the stator windings to prevent emergency or pre-emergency situations. Meanwhile, direct measurement of the temperature of the stator windings is not always possible. The purpose of this work is to develop a mathematical model for controlling the temperature of the stator windings of an asynchronous electric motor with a squirrel-cage rotor at a known temperature of the motor housing. The work is based on a method for determining the amount of heat transferred through the stator of an electric motor, which is represented as a flat wall. A mathematical model is presented that makes it possible to determine the temperature of its heating with a sufficient degree of accuracy based on the known geometric parameters of the motor stator and the temperature of its housing. The theoretical calculations were confirmed by experimental data obtained when the motor was opera-ting in various modes. As a result of the conducted research, the data confirming the operability of the proposed method for determining the temperature of the windings of an asynchronous motor (including the use of non-contact way) were obtained. Further work can be aimed at improving the mathematical model and the ability to monitor other points of the electric motor winding. It is also necessary to take into account the distribution of heat flows not only radially, but also along the axis of the electric machine.
The steam turbine installations in nuclear power units are of the condensation type. The main parameters affecting the performance of condensation-type steam turbine installations are the steam flow rate at the turbine inlet, the temperature variation, and the flow rate of cooling water entering the condenser. Any change in these parameters directly influences the amount of electrical energy produced by the steam turbine. To study their influence, it is necessary to collect a large amount of data and synthesize a mathematical model. Data collection through measuring and recording equipment is a complex, time-consuming process associated with both the technological time required for gathering and subsequent processing. Simulation modeling is a modern research tool that allows studying energy systems without disrupting the technological process. This modeling involves developing an analogue of an existing object in a graphical software environment where geometric and physical parameters characterizing the object’s properties are defined. The results obtained from solving the simulation model must be compared with data from characteristic operating modes of the examined object. The present paper aims to develop a simulation model for assessing the performance of a condensation-type steam turbine installation of a nuclear power unit model K-1000-60/1500-2. This steam turbine installation is typical for nuclear power units of the VVER-1000 type. The data obtained from the simulation model will be used to construct a mathematical model determining the parameters characterizing the operation of the condensation steam turbine installation.
Energy consumption is currently growing at an accelerating pace, evidenced by the mechanization of industrial and domestic sectors, rising energy costs for quality of life, and the advent of electric vehicles. At the same time, the rational and efficient use of energy sources is becoming increasingly important. In particular, the use of power active filters (PAF) is an urgent area in the electric power industry. The advantage of PAF is the ability to simultaneously compensate for both the reactive power of the electrical load at the fundamental frequency and higher harmonic distortion, which significantly improves the quality of electricity in distribution networks. The implementation of PAF control systems based on instantaneous power theory (pq-theory) has significantly advanced in recent decades. This approach provides effective compensation in steady-state conditions, but its effectiveness decreases with dynamic load changes. The most advanced PAF control methods are those based on neural networks and digital signal processing. In most cases, an adaptive threshold logic element (Adaline) is used as the basic element of a neural network. This element is a second-order digital FIR filter that can be configured using a steepest descent algorithm. This structure allows adaptive filtering of harmonic components in real time. Furthermore, the use of digital signal processing technologies makes it possible to use adaptive spectral estimation and interference suppression methods, which enable controllers to adjust their parameters in real time when the non-sinusoidal mode in the network changes. This is especially important when working with pulsed electrical loads, characterized by rapid changes in the spectral composition of the current. The present article analyzes known methods for controlling the PAF for electrical circuits when connecting a pulsed electrical load. It was found that the adaptive method is the most effective one in terms of minimizing the harmonic distortion coefficient (THD) of the current with a transient settling time of t £ 0,01 s, where the THD after connecting the PAF is 1.57%. This confirms the high efficiency of intelligent control algorithms for ensuring power quality in modern electric power systems.
The presented work contains the main results of a study devoted to determining the optimal geometry of the flow part of a radial-axial turbine intended for use in the supercharging system of a piston engine. A series of works devoted to studying the features of the functioning of turbines of this type under conditions of pulsed supply of the working fluid was used as a theoretical basis. The relevance of the present work is due to the need to create highly efficient radial-axial turbocharger turbines used in the engine industry. A mathematical model based on the calculation of a turbine stage at the average radius was used in both direct and inverse formulations. The direct formulation was used to evaluate the efficiency of the turbine in the turbocharging system of a piston engine. The inverse formulation, combined with the Lagrange multiplier me-thod, allowed for the determination of the preliminary geometry of the flow path of the expe-rimental turbines. A quasi-closed mathematicalmodel of aturbochargedpistonengine has beendevelopedformoreaccuratesimulationofturbine operation underconditions of unsteadyexhaustflow, taking into accountthermogasodynamicprocessesin the cylinder,exhaustductandtur-bocharger. The numericalsolution of thismodel made it possible to obtain the characteristics of the studiedturbinesoperatinginrealconditions of unsteadyflow. The results of a comprehensivecomparison of experimentalturbinesdesignedusing the Lagrangemultipliermethodand the standardturbine of the TKR-14C-27turbochargershowedthat the experimentalturbines are more efficient than the standardturbine in theentirerange of parameters. Theseresults made it possible to proposeanewgeometry of the flowpart of the turbine of the TKR-14turbocharger, which providesmoreefficientoperation of the non-stationary gas dynamicaction of the pistonpartwithimprovedefficiencyof the superchargedengine as awhole.
This paper presents the results of a study of overall fuel consumption reduction for electricity generation in the Belarusian Integrated Energy System (IES). The solution is relevant for combined heat and power plants at industrial sites with significant non-return rates of process steam condensate, viz. Novopolotsk CHPP, Mozyr CHPP, and Grodno CHPP-2. The essence of the modernization lies in the beneficial use of heat from the steam turbine condenser circulation circuit to heat makeup water. Calculations are provided for units with PT-60 and PT-70 steam turbines which are the most common types in the Belarusian IES. Implementation of this solution at the CHP plant requires the installation of an absorption heat pump (AHP), which is driven by flue gases extracted from the steam boiler gas duct. The calculation is based on the condition that steam flow to the condenser is maintained constant before and after the modernization, which also leads to a slight reduction in the turbine unit’s electrical power. As a result, for all plants increase of efficiency factors were achieved, which are energy, electrical, and exergy efficiencies. The greatest reduction in annual fuel consumption was achieved for power units with high process steam extraction flows and a significant operating hours per year. When implementing this measure on the PT-60 and PT-70 turbine units of these plants – a total of five units – the annual reduction in primary fuel consumption in the power system will reach 12.8 thousand tons of coal equivalent (tce) per year (with a specific fuel consumption of 302.8 gram tce per kWh for the reference power plant). This solution not only reduces the cost of electricity production, but also reduces greenhouse gas emissions, which is one of the goals of sustainable development.
Modern transformer diagnosing is a lengthy and costly undertaking. A series of complex tests is often necessary, as modern diagnostic methods do not always clearly indicate the of electrical machines and transformers is largely determined by the reliability of the windings, which, in turn, is largely dependent on the condition of the winding insulation. Traditional test methods include measuring various parameters such as short-circuit impedance, no-load loss, transformation ratio, magnetization current, winding resistance and others. Currently, one of the most promising diagnostic methods is the frequency response method. The frequency response method has found wide application in detecting and assessing transformer damage during transportation. Also, this method, using a single set of measurements, provides information on the mechanical condition of the magnetic core, windings, and pressing structure. It has proven its ability to detect damage in windings during short-circuit resistance tests. This detection method complements visual inspection, as it makes it possible to detect small changes in the size of the windings, which are not always visible. Yet, small movements of taps and other parts are not always easily detected using frequency characteristics. In this paper, a method based on frequency response analysis using the method of three voltmeters and convolutional neural networks is proposed for detecting and classifying winding defects.
The agro-industrial complex of the Republic of Belarus, whose products account for about 7.0 % of gross domestic product (GDP), is an important sector of the country's economy, which ensures food security and a high share of exports. Belarusian products are exported to 117 countries. Reliable energy supply plays a key role in the stabilization and efficiency of the development of the agro-industrial complex of our country. Given global economic and environmental challenges, the global trend toward a transition to low-carbon energy and a sustainnable economy, as well as volatile energy prices, the design of an effective strategy for the development of the agricultural sector’s energy complex is particularly relevant. An important aspect of increasing the reliability of agricultural energy supply is the growth of resilience to emergencies related to natural disasters, leading to short-term, but very sensitive damage and destruction caused to industrial facilities as a result of disruption of energy supply. The article presents the results of a comprehensive study of energy consumption efficiency in the agro-industrial sector of the Republic of Belarus; based on these results an analysis of existing problems is made and recommendations for improving the efficiency of energy resources use are proposed. The implementation of these recommendations should not only increase the competitiveness of the agricultural sector, but also ensure the sustainable development of the economy as a whole. Also, it is shown that the introduction of new technologies into the energy supply of the agro-industrial complex of Belarus can significantly increase the economic efficiency of energy supply to small towns and rural areas. It is proposed to create distributed integrated energy systems (to be used as core energy supply facilities) based on energy hubs that combine existing electric, gas distribution and heating networks to optimize the use of traditional and local energy resources. The innovative solutions will not only reduce production costs and improve the reliability of energy supply, but also optimize the consumption of traditional energy sources, which is becoming particularly relevant in the context of growing interest in renewable energy sources, the need for the diversification of energy resources, and decarbonization of power industry and manufacturing.
LEDs are based on a semiconductor crystal with a surface in Miller indices (111), formed by diatomic molecules of gallium arsenide or indium phosphide in bulk clusters. A structure of positively charged ions of gallium and arsenic atoms in gallium arsenide and as well as of an exchange interaction between positively charged ions of indium atoms arises inside them. The positively charged skeleton is compensated by an electron cloud. An electric current of conduction and displacement occurs in LEDs. The crystal surface is covered with a monolayer of diatomic molecules with the formation of quadrate voids, which can accommodate single impurities (up to four different atoms) with the formation of negative ions. A crystal of gallium arsenide or indium phosphide with an admixture is used as the cathode, and aluminum is used as the anode. The ionization of negative ions of various impurities occurs under the influence of temperature and an applied external electric field. After ionization, free electrons arise which form an electric conduction current in the columnar void. An electric conduction current determines the power of light emission. The size of the light-emitting surface of the LED is ~10´10 nm. In the contact zone of the anode and cathode, a partial scattering of the electron flow of the conduction current occurs, which significantly reduces the power of light emission. A scattering is caused by the energetic transition of a free electron from the upper energy level to the underlying level according to the scheme as it occurs in atoms. The volt-ampere characteristics for LEDs are determined by measuring the electric bias current in the external circuit and the voltage at the current source. These data do not allow us to analyze the operation of the LED, since the LED operates on the conduction current that occurs inside it. It is difficult to determine what proportion it makes up of the total displacement current measured in the external circuit. As a result of the theoretical calculation, the optimal electrical conduction current in the LED should not exceed 10 mA, while the supply voltage ranges from 1.3 to 3.5 V. The LED is powered only through ballast resistance using pulse width modulation.
Heat demand forecasting is necessary to achieve optimal management of building energy consumption. The purpose of this article is to identify the most important factors influencing the accuracy of forecasting heat consumption of buildings using neural networks, which is in line with the national strategy for the development of artificial intelligence of the Russian Federation. The article studies the dependence of modeling accuracy on various combinations of environmental parameters, as well as on the application of different activation functions of neural networks, widely used in the practice of creating artificial intelligence systems. It is demonstrated that machine learning models based on a large number of data on thermal consumption have great possibilities in predicting real patterns and trends of consumption, and the value of the average absolute percentage error of the best prediction model is comparable to the value of the maximum limit of the tolerable relative error of thermal energy measurements by the measuring channel of the heat meter. On the basis of data obtained using the developed system of remote monitoring of individual heating points of buildings, a comparison of actual values of heat consumption and values of heat consumption obtained using the prediction model was demonstrated. Savings of energy, heat carrier and other things at the object cannot be measured directly, because the savings represent the absence of consumption, so a universal approach using artificial intelligence for a technically sound and economically feasible method of predicting the results of the application of energy-saving solutions to compare the measured energy consumption before and after the implementation of energy-efficient measures may allow to improve the efficiency of decision-making in the field of saving energy resources.
