ISSN 2223-0858 (Online) Subject: theoretical and applied sciences, technology and industry in the field of energy and automation Year established: 2009 Founders: National University of Life and Environmental Sciences of Ukraine Published 4 times a year Media identifier R40-02287. The National Council of Television and Radio Broadcasting of Ukraine Decision No. 1796 of 21 December 2023, protocol No. 31. Speciality DAK: Technical Sciences Languages of the publication: Ukrainian, English Address: Heroiv Oborony st., 12, Kyiv-03041, Ukraine Phone: +38 044 527 85 22 Indexed in the following international scientometric databases: Google Scholar AGRIS MIAR BASE ResearchBib DRJI Ulrichsweb
Національний університет біоресурсів і природокористування України
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Research on the influence of the dynamic viscosity of raw material fermented in a biogas reactor on heat distribution
Biogas plants are becoming increasingly popular among industry and domestic consumers. This has led to increased interest in conducting research to increase the profitability of such plants. First of all, researchers are focusing their attention on creating systems that will satisfy the conditions for anaerobic digestion and at the same time consume a minimum amount of electrical energy for mixing and heating the substance. After all, for fermentation, raw materials with different physicochemical composition are used, which significantly affects energy costs. The aim of the work is to study the influence of the dynamic viscosity of the raw materials fermented in a biogas reactor on the change in the Reynolds criterion and heat transfer coefficients from the rotating heater to the raw materials. The article presents a mathematical model for conducting theoretical studies. The work considers the change in the dynamic viscosity of the substrate in the range from 0.01 to 0.1 Pa·s. It was found that when the dynamic viscosity of the raw material changes in the range from 0.01 to 0.1 Pa·s, the Reynolds criterion and heat transfer coefficients change according to an exponential law, which is confirmed by the graphical dependencies obtained during the research and presented in this work. The results obtained will further allow us to establish a rational rotation frequency of the mixing device combined with a heating device, taking into account the change in the dynamic viscosity of the raw material, to create and maintain a favorable microclimate for the anaerobic process with the maximum possible formation of biogas. Key words: reynolds criterion, energy consumption, heat transfer coefficient, dynamic viscosity of raw materials, fermentation, heat transfer coefficient, mixing
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Mathematical modeling of the propagation of electroacoustic shear waves in a layered periodic medium “Piezoelectric - gap”
The paper developed a method for constructing dispersion relations for bulk, surface and normal electroelastic shear waves propagating in layered-periodic media formed by repeating a "generating" package consisting of a piezoelectric layer and a vacuum layer that does not have electrical properties. As a result of the analytical calculations, dispersion relations for surface, normal and bulk electroelastic shear waves were obtained. CdS was considered as a piezoelectric material. The obtained dispersion relations were numerically analyzed for different layer geometries and physical properties of materials forming the "generating" package. . Numerical analysis showed that a feature of the obtained bulk wave spectrum is that in the range of changes in the wave number and circular frequency, the zone boundaries do not intersect. The spectrum of normal waves is formed by a set of dispersion curves, which is localized in the zones of transmission of bulk waves except for one dispersion curve from the set. This curve is a dispersion curve for surface modes. The set of dispersion curves of normal modes consists of n curves (n is the number of electroelastic "generating" packages in the structure). The influence of the physical-mechanical and geometric parameters of the layers on the structure of the blocking and transmission zones has been studied, and the influence of the piezoelectric effect has also been investigated. Based on the approaches proposed in previous works, the problems of bulk, surface and normal electroelastic waves are reduced to the study of the properties of the transmission matrices of the "generating" package of layers, through the elements of which the desired dispersion relations are expressed. In the work, it was possible, using the condition of metallization on the outer surfaces of the package, to write the dispersion relations through the elements of the second-order matrices instead of the fourth, which made it possible to simplify the analysis of the dispersion equations. Key words: bulk, surface and normal shear waves, periodic layered structure, piezoelectric, layer with vacuum properties, transmission zones, blocking zones of bulk waves
Research installation for growing plants in a high voltage electric field and under various optical radiation
The study of the influence of high-intensity electric fields and various optical radiation on plant growth and development is a promising direction in agronomy and agroecology. The aim of this work is to develop and test an experimental setup that allows creating controlled conditions for growing plants under the influence of electric fields and optical radiation of various spectra. The setup consists of a system for creating high-intensity electric fields, LED light sources, a climate chamber, and a monitoring and data analysis system for recording growth parameters and physiological processes of plants. The main goal of the study is to assess the effectiveness of the influence of these factors on photosynthetic activity, growth rate and plant yield, as well as to determine the optimal parameters for stimulating their development. Experiments have shown that electric fields can significantly increase the growth rate of plants, and light spectra (red, blue, ultraviolet) affect the efficiency of photosynthesis and the development of the root system. In addition, the combined effect of electric fields and optical radiation helps to improve crop yield and plant resistance to stress factors such as diseases, pests and extreme climatic conditions. High-voltage electric fields also play an important role in stimulating plant growth. The effect of electric fields on biological objects is widely studied in various fields of science, in particular in agronomy. It has been established that electric fields can affect plant growth by stimulating ionic and electrochemical processes in cells, which improves the absorption of water and nutrients from the soil. This opens up new opportunities for improving the quality and quantity of the crop. Key words: electrotechnological complex, energy efficiency, high-voltage electric field, automation
Visual assessment of raw materials in premix production using OpenCV
The quality control of premix components is a crucial stage of their production. It directly influences a number of final product characteristics, including homogeneity, granulometric properties, and the effectiveness of the premix ingredients. This study highlights the relevance of using computer vision based on the OpenCV library for image processing of salt samples, as well as the application of deep learning with TensorFlow for automated quality classification. The results indicate whether the proposed tools are suitable for an efficient quality control process, enabling a reduction of human factor influence and improving the accuracy of defect detection. Key words: computer vision, salt quality assessment, premix production, machine learning, OpenCV, TensorFlow
Modeling of a solar photovoltaic converter in the specialized Matlab software
The developed model of a solar photovoltaic converter (SPC) based on a single-diode model, taking into account shunt and series resistances, photocurrent, and diode reverse current, is used for analyzing the electrical characteristics of the SPC and determining the maximum power point (MPPT) under varying illumination and temperature conditions. The model is implemented in the MATLAB environment, providing the capability for straightforward simulation of physical processes in photovoltaic cells. The proposed method allows obtaining accurate current-voltage characteristics, taking into account the temperature and illumination of the SFС. The implementation of the model in MATLAB simplifies and accelerates its use for the study of MPPT algorithms and autonomous photovoltaic systems. The built-in MATLAB algorithm is used to calculate the current, since the equation of one diode is transcendental and nonlinear with respect to current, and direct analytical methods do not solve it. The results obtained will increase the speed of obtaining current-voltage characteristics of the SFС and determining the maximum power point without the need for lengthy experimental measurements. This will accelerate the development and optimization of autonomous and integrated photovoltaic systems, evaluate the efficiency of the SFP under various conditions, and also simplify testing and verification of MPPT algorithms in the MATLAB environment. Key words: solar photovoltaic converter, resistance, current-voltage characteristic, voltage source, mathematical model
The thermal method in the diagnostic and protection system of an electric motor
Induction motors (IMs) are the most widespread electrical consumers in port and ship electrical complexes. The share of IMs among all electrical receivers operating at voltages up to 1000 V reaches up to 70 % of the total number. The main factor that shortens the service life of electric machines operating under conditions of increased dustiness of the environment is the accelerated aging of stator winding insulation. The dust layer thickness on the upper part of the end winding of motors with a power of 50 kW or more ranges from 2 to 5 cm. The accumulation of dust on the surface of the IM winding insulation leads to reduced heat dissipation and local overheating of the insulation under the dust layer. The development of a method for diagnosing the causes of thermal loading of stator winding insulation and a system for thermal protection of IMs, determining the conditions for preventive maintenance, as well as creating algorithms and software for devices providing thermal protection of induction motors, is therefore a relevant task. Key words: induction motor, thermal protection, local overheating of insulation, software, thermal protection of an electric motor
Development of a training stand based on the MKN1063 cabinet for the practical preparation of students in electrical installation and automation
The article presents the results of a study aimed at addressing the problem of insufficient practical training of students in electrical engineering specialties in the areas of installation, commissioning, and operation of electrical equipment. An analysis of the industrial internship conducted at the company LLC "SichEnergo" revealed that a significant portion of students lack the necessary competencies to work with cabinet electrical equipment. In particular, difficulties were identified during installation work in the confined spaces of electrical cabinets, insufficient skills in cable routing, installation of modular equipment on DIN rails, execution of switching operations, and connection of circuit breakers, relays, contactors, PLCs, and other apparatus. A separate methodological issue was the impossibility of organizing group training directly at real, operating cabinets due to limited access to the working area. A review of current research in the field of engineering education showed that, despite the development of VR/AR technologies, digital simulators cannot fully replace physical installation stands. Virtual tools are effective for visualizing and familiarizing students with system construction principles; however, detecting and correcting cable connection defects, proper use of tools, organizing the installation space, and performing operations in real conditions require hands-on work with actual components. Therefore, the optimal training model is a combination of digital technologies and physical constructions that can accurately simulate the production environment. To address this issue, a universal training installation stand was developed based on the industrial MKN1063 electrical cabinet. The stand's design includes typical electrical installation components, programmable logic controllers, modular relays, circuit breakers, communication modules, and other equipment, allowing students to practice both basic and advanced training scenarios aligned with modern production requirements, including Smart Grid and IoT infrastructure. The stand is equipped with transparent side panels, enabling the entire group to simultaneously observe the installation process, analyze execution techniques, and correct errors. A key innovation of the stand is the ability to perform installation first on a horizontally placed panel and then on its vertical placement inside the cabinet. This approach allows for accurate replication of real production conditions, practice of the full installation cycle, and development of competencies required for working with cabinet equipment. The modular layout provides flexibility in configuring training tasks, including disassembly, troubleshooting, and maintenance operations. Results of the trial implementation demonstrated increased accuracy in performing installation tasks, improved teamwork skills, and higher compliance with electrical safety requirements. Key words: installation of electrical equipment, control cabinet, panel, stand
System of monitoring and management of electricity consumption in the micro-energy system of a territorial community with own sources
The article considers the practical aspect of organizing the functioning of a microgrid of a housing cooperative of household owners as a prototype for implementing European principles of decentralized energy supply in accordance with the new Law of Ukraine "On the Electricity Market". The study deals with the analysis of the features of structuring microenergy system sources and the principles of implementing monitoring and management of electricity consumption based on the use of modern software and hardware complexes. The advantages of using cloud technologies (Oracle) for data processing, forming electricity consumption balances and forecasting in real time are proven. The authors investigated the possibilities of integrating heterogeneous generation sources (external network, diesel generator, solar power plants, electricity storage systems) into a single microgrid with the ability to operate both when connected to the external network and in isolated mode (in energy island mode) with its own metering and dispatching system. Ways for further development of micro-energy systems of territorial communities in Ukraine are proposed, taking into account European experience and current regulatory and legal support. Key words: microgrid, energy island, decentralized energy supply, monitoring system, electricity consumption management, power balancing
Integrated assessment of the quality of microprocessor-based relay protection
The article discusses the problems of assessing the effectiveness of microprocessor-based relay protection of power system facilities. The relevance of the study is due to the importance of relay protection devices in ensuring timely detection and elimination of emergency modes, preventing equipment damage, and maintaining the stability of the power system. Traditional approaches to assessing performance quality boil down to taking into account equipment and operational losses or are limited to the percentage of correct relay actions, which does not always allow for an accurate assessment of system efficiency. The purpose of the study is to develop an integrated criterion for evaluating the effectiveness of microprocessor-based relay protection, which takes into account functional and metrological losses caused by measurement errors, response delays, and other features of the implementation of protection algorithms. To analyze losses, it is proposed to classify them into groups: functional-metrological, related to the adjustment of settings and the properties of selectivity and sensitivity; indirect hardware, arising from component failures and personnel errors; independent of settings, including damage to equipment and infrastructure. For quantitative assessment of effectiveness, an integral indicator <!-- [if gte msEquation 12]><m:oMath><m:r>m</m:r><m:d><m:dPr><m:ctrlPr></m:ctrlPr></m:dPr><m:e><m:r>E</m:r></m:e></m:d></m:oMath><![endif]--> <!-- [if gte vml 1]><v:shapetype id="_x0000_t75" coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="m@4@5l@4@11@9@11@9@5xe" filled="f" stroked="f"> <v:stroke joinstyle="miter"/> <v:formulas> <v:f eqn="if lineDrawn pixelLineWidth 0"/> <v:f eqn="sum @0 1 0"/> <v:f eqn="sum 0 0 @1"/> <v:f eqn="prod @2 1 2"/> <v:f eqn="prod @3 21600 pixelWidth"/> <v:f eqn="prod @3 21600 pixelHeight"/> <v:f eqn="sum @0 0 1"/> <v:f eqn="prod @6 1 2"/> <v:f eqn="prod @7 21600 pixelWidth"/> <v:f eqn="sum @8 21600 0"/> <v:f eqn="prod @7 21600 pixelHeight"/> <v:f eqn="sum @10 21600 0"/> </v:formulas> <v:path o:extrusionok="f" gradientshapeok="t" o:connecttype="rect"/> <o:lock v:ext="edit" aspectratio="t"/> </v:shapetype><v:shape id="_x0000_i1025" type="#_x0000_t75" style='width:33pt; height:16.5pt'> <v:imagedata src="file:///C:\Users\SVV\AppData\Local\Temp\msohtmlclip1\01\clip_image001.png" o:title="" chromakey="white"/> </v:shape><![endif]--> is proposed, which takes into account all elements of the relay protection channel and allows assessing the probabilistic characteristics of losses and the potential effect of protection. To assess reliability, a normalized failure rate <!-- [if gte msEquation 12]><m:oMath><m:sSub><m:sSubPr><m:ctrlPr></m:ctrlPr></m:sSubPr><m:e><m:r>m</m:r></m:e><m:sub><m:r>∑</m:r></m:sub></m:sSub></m:oMath><![endif]--> <!-- [if gte vml 1]><v:shape id="_x0000_i1025" type="#_x0000_t75" style='width:19.5pt;height:18pt'> <v:imagedata src="file:///C:\Users\SVV\AppData\Local\Temp\msohtmlclip1\01\clip_image003.png" o:title="" chromakey="white"/> </v:shape><![endif]--> is used, which includes relay failures, incorrect protection actions, and personnel errors. An integrated approach allows for a comprehensive assessment of the efficiency, technical excellence, and economic feasibility of using microprocessor relay protection devices, predicting their behavior in emergency situations, optimizing settings, and increasing the adaptability and reliability of the system in real operating conditions. The use of the probabilistic-statistical method ensures objectivity of assessment and allows making informed decisions on the modernization and optimization of relay protection systems for power facilities. Key words: wind power installation, wind potential, wind speed, repeatability of wind speeds, distribution function, forecasting
Thermal load of buildings as a parameter of energy efficiency of the heating system
Reducing heat energy consumption and increasing energy efficiency at all stages of heat transformation in district heating systems is a key measure to combat climate change, which is the goal of the EU energy policy. The value of the calculated heat load (CHL) is the basis for determining the heat carrier consumption in the heat networks of district heating systems. However, the inconsistency of regulatory documentation and changes taking place in the field of heat supply have led to the fact that today there is no generally accepted methodology for determining this value. The purpose of the study is to compare existing methods for determining the value of CHL for heating needs and to provide recommendations for the correct determination of this indicator for different categories of buildings. The general principles of calculating the heat load for heating and ventilation systems of residential and public buildings are considered. Problems that arise during the determination of the value of the connected heat load for district heating systems are noted. Recommendations are given on ways to solve such problems/ Key words: connected heat load, calculated heat losses, thermal resistance, heating and ventilation
Impact of solar energy application on improving the energy performance of continuous-flow heat pump grain dryers
Grain drying is an essential stage of post-harvest processing. Utilizing renewable energy sources, particularly heat pumps combined with solar energy, is one of the methods for improving the process's energy efficiency. Brief information is provided on the use of heat pumps in combination with various approaches to solar energy utilization. A detailed schematic diagram of a continuous-flow grain dryer is considered, which involves the sequential use of two drying agent heating systems: a solar air heater and a heat pump. Within the scope of this article, an analytical model for determining the energy efficiency of this schematic solution is presented along with the calculation results. Recommendations are provided for the optimal use of the heat pump in combination with the solar heater in continuous-flow dryers with drying agent recirculation. The research findings will be useful for further scientific research and for developers of modern grain drying systems. Key words: grain dryer, energy efficiency, recirculation, heat pump, solar collectors, solar heat pump, solar energy, recuperation, flow dryers, grain moisture
Development of new heat exchanger design for the use of exhaust gases of ice in cogeneration plants. Hydraulic calculation
New design of heat exchanger for utilization of exhaust gases of an internal combustion engine, which is part of cogeneration plant, is proposed. This design differs from traditional designs by the presence of compact bundles of small diameter pipes in the absence of gaps between adjacent pipes in the longitudinal direction of gas coolant. Method of hydraulic calculation of heat exchanger-utilizer has been developed, which makes it possible to determine the power of smoke exhauster when removing combustion products and pump for pumping water coolant. It was found that new design of heat exchanger has significantly lower pressure losses in the intertube channel of heat exchanger-utilizer compared to known designs. Capacities of smoke exhauster and water pump have been determined, which can be used when selecting heat energy equipment for cogeneration plants based on internal combustion engines. Key words: heat exchanger, local pressure losses, pressure losses due to friction, smoke exhauster, water pump
The influence of stator winding resistance imbalance of an induction motor: evaluation of phase current asymmetry
Asymmetry of the active resistances of stator windings occurs in approximately 30 % of repaired induction motors operating in power complexes of seaports, industrial enterprises, and ships. The resistance asymmetry causes current imbalance in the windings even under symmetrical supply voltage. In a non-symmetrical network, the asymmetry of active resistances can both increase and decrease the current asymmetry coefficient. The use of the Mathcad system enables the calculation of the current asymmetry coefficient depending on the deviation of the supply voltage, variation of stator winding resistances, load current, and supply frequency. Key words: induction motor, active resistance asymmetry, voltage asymmetry, current asymmetry coefficient
Investigation of spectra and of aggregation of vanadium phtalocyanine molecules in two-component solutions
It was studied the electronic spectra of vanadium phtalocyanine dye molecules in diluted and concentrated solutions as well as in low- and high-polarity solvents. In diluted low-polarity solvent VOPc molecules exist in monomer state, whereas dye molecules concentration increase leads to appear of dimer formation. It was shown that using of mixed acid-water solvent is an effective approach to controlled aggregation of dye molecules. Main parameters of the influence on VOPc aggregation are concentration of water ingredient and associates “growth” time. In a concentrated high-polarity solvent, the dye molecule is in the form of a monocation solvated by solvent molecules and unable to interact with other dye ones. In this case, it is just the monomolecular absorbance spectrum that is characteristic for the solution. As water is added, the dye molecular interaction becomes possible due to the solvatic shell destruction, and association of organic molecules occurs. In our case, this results in the appearance of a broad 980 nm band in the absorbance spectrum. Using acid-water mixtures and varying the water concentration therein, the dye aggregation process can be controlled as well as the number of molecules in an aggregate. So the appearance of absorbance bands at 775 and 690 nm is observed which can be attributed to the formation of sandwich-type dimers (H-dimers). As the water concentration increases, large dye aggregates are formed. At high water concentrations, micro-scale single crystals may grow. The “growth” process can be observed in absorbance spectra as the appearance of the 980 nm band and its further intensity increase, long-wavelength shift and broadening. Above features demonstrate an approach to size-controlled preparation of dye molecules aggregates in polar – non-polar solutions mixture for farther use in photovoltaic and sensors applications. Key words: nano-size organic dye crystals, association of dye molecules, enhancement of electronic properties of aggregated dye molecules, seft-assembling of molecules
Comprehensive assessment of power quality in a low-voltage node with distributed generation and energy storage: evidence from field monitoring
The objective of this study is to conduct a comprehensive assessment of power quality parameters in a low-voltage node incorporating photovoltaic modules and an energy storage system, based on long-term field monitoring. The methodology involved analyzing time series of voltages, currents, active power, power factor, and total harmonic distortion recorded with a 15-minute resolution during the period September 2024 – March 2025. Data were segmented according to import and export modes of energy flow, resampled, and subjected to event-based detection of intervals deviating from EN 50160 and IEEE 519 standards. The results demonstrated that voltage consistently remained within permissible limits, whereas approximately 81% of measurements indicated current harmonic distortion exceeding 5%. The absolute power factor was not lower than 0.9 in 90% of cases, but declined to 0.85–0.90 in nearly 10% of intervals, primarily due to harmonic distortion and reactive power exchange. Moreover, the analysis confirmed the high stiffness of the supply network, which accounts for the stability of voltage parameters despite pronounced current harmonics. The findings underline the necessity of implementing active or passive filtering measures to mitigate harmonic distortion and maintain power factor stability. Key words: power quality, harmonic distortion, power factor, grid stiffness, short-circuit capability, low-voltage networks, municipal facilities
Improving the efficiency of a photovoltaic converter using the maximum power point tracking method
Methods and models of power consumption control systems for energy generation by solar photovoltaic converter (SPC) is an urgent task of finding the maximum power point (Maximum Power Point Tracking, MPPT) to increase efficiency. The results of mathematical numerical modeling in the MATLAB environment and experimental research using the physical model of SPC confirm the effectiveness of the developed control system. The input conditions included variable insolation, which was specified as a combination of two sinusoidal signals with an additional restriction within 200–1200 W/m², which allows modeling dynamic weather conditions, for example, the passage of clouds or partial shading. During the simulation, the voltage and current on the load were calculated through the conditional linear equivalent of the SPC taking into account the load resistance, which was changed according to the Perturb and Observe (P&O) algorithm. The developed system provides maximum power support throughout the entire simulation period, which confirms the practical value of the system for controlling SPC in energy systems. Key words: solar photovoltaic converter, resistance, maximum power point, mathematical model, perturb and observe
Research on the influence of frequency control methods on the energy efficiency of an automated electric drive of a pumping station
Pumping units are widely used for pumping various liquids, and most of all in water supply and drainage systems. Water consumption is a random function of time during the day (day, evening, morning) and depends on the season (summer, winter or spring). The efficiency and cost-effectiveness of cold and hot water supply, heating, drainage and water treatment enterprises of cities, urban and rural areas can be significantly increased through automation and the introduction of regulated electric drives. The article considers methods for increasing the energy efficiency of an automated electric drive of a pumping station, developed on the basis of a frequency converter using a PID regulator and an MRS controller. Existing technologies for regulating pump performance, such as the use of throttle valves and frequency converters (FCs), are analyzed. To study the impact of frequency regulation with a PID regulator and a digital twin on the energy efficiency of pumping units, a simulation model has been developed in the Matlab application package. The conducted studies show that the use of frequency control ensures the maintenance of the required technological parameters of the hydro network, reducing energy consumption compared to throttling with an unregulated pump drive, since operation at constant speeds leads to significant energy losses, especially in partial load modes. The use of an MPC controller allows you to improve the quality of the regulation process compared to a PID regulator, thereby increasing energy efficiency, anti-cavitation effect, and predictive diagnostics of defects reduces unplanned downtime. The potential for reducing energy consumption and improving the efficiency of pumping stations when using such methods has been assessed. The main advantages and disadvantages of frequency control, as well as the prospects for the development of these technologies in the context of energy saving, have been identified. Key words: automated electric drive, water pumping station, frequency control, MPC, digital twin, PID regulator, energy efficiency
Intelligent system for monitoring and forecasting the state of electrical equipment based on Microgrid
The concept of building an intelligent system for monitoring and forecasting the technical condition of electrical equipment within a decentralized energy system of the Microgrid type is considered. The architecture of the Predictive Maintenance (PdM) system is proposed, based on the use of sensor networks, Internet of Things (IoT) technologies, artificial intelligence (AI) and big data analytics (Big Data). A mathematical model for assessing the technical condition of electric motors is developed, which takes into account changes in the main electrical and mechanical parameters (current, voltage, temperature, vibrations, speed). The structure of the PdM process is proposed, which includes the stages of collecting, processing, analyzing data and forming predictive solutions based on machine learning algorithms. Key words: Microgrid, Predictive Maintenance, monitoring, electric motor, artificial intelligence, Internet of Things, Big Data, modeling, technical condition, energy efficiency
Experimental study of environmental factors' impact on surface leakage currents of high-voltage support insulators
Ensuring the reliability of high-voltage insulation systems is critical for the safe and efficient operation of power equipment. Surface leakage currents, formed under the influence of atmospheric and anthropogenic factors, accelerate the aging of insulation materials, reduce their dielectric strength, and increase the risk of emergency failures. Particular attention is given to the combined impact of relative humidity, temperature fluctuations, surface contamination, and wind speed, which together create highly unfavorable conditions for the operation of insulation systems and necessitate the implementation of automated approaches to monitoring and managing their condition. The aim of this work is to experimentally determine the influence of key climatic and anthropogenic factors on the leakage currents of support insulators, to assess the relative contribution of these factors, and to construct generalized graphical dependencies. The results obtained can be used to predict the performance of insulation systems and to develop automated methods for optimizing the operating modes of power equipment. The research was conducted on IOS-35-1000 UHL insulators operated at substations in the central region of Ukraine. It was found that the dominant influencing factors are relative humidity (30%), negative temperature difference (25%), and surface contamination (20%). Absolute humidity, duration of moisture exposure, and wind speed have a secondary effect on leakage current, with wind partially reducing surface conductivity. The experimental graphical dependencies reflect the dynamics of conductive layer formation under various moistening conditions. Critical operating conditions for insulation systems arise when high humidity, negative temperature differences, and the presence of a hygroscopic contamination layer are combined. The results obtained can be used to predict the reliability of insulation structures and to improve automated insulation condition monitoring systems. Key words: high-voltage insulator, leakage current, surface contamination, atmospheric factor, experimental study.
Speed optimization of positional electric drives using the maximum principle
The performance quality of many technological processes depends to a large extent on the inertial properties of executive devices. Positional electric drives with servomotors, which have integrating properties, are widely used as executive devices of automatic control systems. Optimizing the speed of such electric drives makes it possible to improve the quality of technological processes, reduce dynamic adjustment errors caused by the influence of the inertia of the executive device. The maximum principle is a convenient means of determining the optimal control law as a function of phase coordinates, that is, a means of synthesizing optimal regulators in closed systems, and a function of time, that is, a means of finding optimal software controls in open systems, which are positional electric drives with relay control. The purpose of this work is to substantiate the application of the maximum principle for the problem of optimizing the speed of positional electric drives and to find an analytical solution to this problem. Key words: optimal control, maximum principle, electric drive, optimality criterio
Influence of voltage deviations on the drive characteristics of working machines with dc motors of independent and parallel excitation at Mc=const
Voltage deviation in DC motors leads to losses that have an electromagnetic and technological component. Studies on the influence of voltage deviation and asymmetry on the technological and energy characteristics of working machines and mechanisms with an asynchronous electric drive have shown that when they deviate, productivity decreases and specific energy consumption increases. However, there are no studies on the influence of voltage deviation on DC electric drives. The purpose of the study is to establish the influence of voltage deviation in electric drives with DC motors of independent and parallel excitation on the technological and energy characteristics of working machines with a static resistance moment independent of angular velocity. When the voltage deviates, the angular velocity of DC motors of independent and parallel excitation changes, which causes a change in the productivity of the working machine. In DC motors of independent excitation, the dependence of the productivity of the working machine on the voltage change is linear, and in DC motors of parallel excitation, the productivity of the working machine during voltage deviation changes according to a complex algorithm. When the voltage deviates, the constant and variable power losses in the DC electric motor change. It is proposed to conduct an energy assessment of a DC electric drive based on specific electricity consumption. The study of the influence of voltage deviation on the energy characteristics of working machines with a constant moment of static resistances, which are driven by DC motors of independent and parallel excitation, was carried out. It was established that with a decrease in voltage, specific electricity losses increase. Key words: DC motor with independent and parallel excitation, voltage deviation, specific power consumption
Method of structural synthesis of the power supply network of critical infrastructure facilities
At present, the urgent problem is to enhance the structural resilience of energy networks against their constant destruction caused by air attacks. The article examines the issue of integrating decentralized generation sources to ensure the energy autonomy of critical infrastructure facilities. The purpose of the study is to improve the structural resilience of energy supply networks for critical infrastructure based on the optimal integration of renewable energy sources, biogas plants, and energy storage systems. To achieve this objective, the problem statement was formulated, and a modified branch and bound method was proposed for its solution. An algorithm for solving the multi-criteria optimization problem of energy network structures was developed. The main results confirm that the optimal structural integration of solar and wind generation, biogas plants, and batteries makes it possible to cover critical loads under forecasted conditions. The implementation of such systems significantly increases the structural resilience of energy systems and creates conditions for the sustainable development of energy-independent communities. Key words: structural stability, power grid, solar, wind generation, energy storage, biogas plants, optimization
Analysis of parallel operation of autonomous wind power plants with asynchronous generators
The article presents an analysis of modern studies dedicated to the parallel operation of autonomous wind energy systems with asynchronous generators. The advantages and limitations of using asynchronous machines in decentralized power systems are considered, particularly their simple design, reliability, and cost-effectiveness. Various approaches to organizing parallel operation are analyzed, including the features of ensuring and maintaining self-excitation, the use of capacitor banks, connection schemes for generators of different capacities, and methods of voltage and frequency regulation. Special attention is paid to the role of mathematical and simulation modeling, as well as experimental studies, which make it possible to evaluate the efficiency of systems under variable operating conditions. The prospects of applying controllers, especially those based on fuzzy logic, to enhance the stability and efficiency of autonomous power systems are also discussed. Based on the analysis, directions for further research are identified, particularly the need for a comprehensive consideration of transient processes, wind speed fluctuations, and the impact of load characteristics on the operation of parallel-connected generators. Key words: renewable energy sources, wind energy, wind power plant, asynchronous generator, parallel work, autonomous work
Development of new heat exchanger design for the use of exhaust gases of ice in cogeneration plants. heat calculation
A new design of a heat exchanger for the use of exhaust gases of an internal combustion engine, which is part of a cogeneration plant, is proposed. This exchanger differs from traditional designs by the presence of compact bundles of small diameter pipes with no gaps between adjacent pipes in the longitudinal direction of the gas coolant movement. A method of heat calculation of heat exchanger-utilizer has been developed, which makes it possible to determine the dimensions of heat exchanger. The results obtained have been analyzed and it has been shown that the new design of heat exchanger-utilizer has a number of advantages compared to the known designs of shell-and-tube heat exchangers. It has been found that the new design of heat exchanger improves the mass-dimensional indicators of heat exchanger-utilizer compared to known designs and can be used in the development of cogeneration plants based on internal combustion engines. Key words: shell-and-tube heat exchanger, method calculation, heat calculation, design, cogeneration plant, tube bundle
Luminescent labeling of leaves for remote monitoring of plants
Luminescent markers are attracting increasing attention as a means of monitoring plant health due to the development of modern technologies for collecting, processing, and storing data necessary for precision agriculture. The combination of optical characteristics (reflection and emission of light) of markers (phosphors) and plant leaves allows remote monitoring, which contributes to the automation of the plant growing process. At the same time, the choice of the phosphor and the method of its application to the plant remains a relevant area of scientific research. In this work the results of the study of optical characteristics such as: diffuse reflection, photoluminescence (PL), and PL excitation spectra of leaves "before" and "after" the application of suspensions of two types: phosphor + water and phosphor + water + PVA, where the phosphor was SrAl2O4:Eu,Dy powder, have been analyzed. It was found that the application of suspensions of both types increases the diffuse reflection of light by leaves in the entire visible region., Three PL bands were observed in the photoluminescence spectra of untreated leaves: one of low intensity with a maximum at 535 nm, and two intense bands with maxima at 685 and 740 nm. The latter two bands of red luminescence correspond to the emission of the molecules of chlorophyll a, while the band at 535 nm may be ascribed to the emission of carotenoids in the leaves. The application of the SrAl2O4:Eu,Dy+H2O suspension practically does not lead to a change in the spectrum of intrinsic "red" PL of the leaves in the region of 625–825 nm. At the same time, for leaves coated with the SrAl2O4:Eu,Dy+H2O+PVA suspension, there is an increase in the luminescence intensity in the region of 450–650 nm, compared to the intensity of the band at 685 nm. The relative intensity of the PL band at 740 nm, however, decreases. It has been demonstrated that the PL spectra of the samples are sensitive to changes in the PL excitation wavelengths, ghat allows for selective excitation of the photoluminescence of the phosphor label and chlorophyll a contained in the leaf. The obtained results indicate the possibility of using the optical properties of leaves treated with suspensions to collect information about the condition of the plant, with the aim of applying the Internet of Things (IoT) concept in crop production. Key words: chlorophyll, light absorption, luminescent marker, photoluminescence
Comprehensive approach to energy efficiency assessment of induction furnaces under unstable power supply
A comprehensive approach to evaluating the energy efficiency of induction furnaces under unstable power supply has been developed, integrating electromagnetic, thermodynamic, and stochastic models. The influence of power grid parameter fluctuations on electromagnetic field penetration depth, eddy current distribution, and temperature gradients in the melt has been investigated. The nonlinear nature of heating power dependence on voltage and frequency deviations has been established. A mathematical model for probabilistic assessment of energy losses under various types of power supply anomalies has been formulated. A methodology for calculating integral energy efficiency indicators has been developed, including the coefficient of variation of efficiency and the probability of ensuring a minimum acceptable efficiency level. A phenomenological analysis of the relationship between power quality indicators and thermodynamic characteristics of the melting process has been conducted. Theoretical principles for constructing adaptive control systems for induction furnaces based on predictive models of power grid fluctuations have been substantiated. The research results create a theoretical basis for developing intelligent control systems for induction melting units capable of ensuring an optimal balance between energy efficiency and product quality. Key words: induction furnace, energy efficiency, unstable power supply, electromagnetic field, stochastic modeling, adaptive control, metallurgical processes
Research on the influence of the specific density of the raw material fermented in a biogas reactor on heat distribution
Biogas technologies are becoming increasingly widespread in industrial and domestic facilities. However, the profitability of biogas production depends on the energy consumption to support the fermentation process, so it is necessary to conduct research aimed at reducing energy costs for heating and mixing the raw material being fermented. Raw materials with different physicochemical compositions are used for fermentation, which significantly affects energy costs. The aim of the work is to study the influence of the specific density of the raw material being fermented in a biogas reactor on the energy costs for mixing and changing the Reynolds criterion. The paper presents the constructed mathematical model and research results. The research considered a wide range of changes in the specific density of the substrate from 750 to 1500 kg/m3. According to the research results, graphical dependences of the change in the Reynolds criterion, heat transfer coefficient and heat transfer coefficient were obtained, depending on the change in the specific density of the raw material and the frequency of rotation of the working body of the mixing device. It has been established that the change in the criterion and coefficients depending on the change in the density of the raw material occurs according to a linear law. The results obtained will allow setting a rational rotation frequency of the mixing device in which the heating device is located from the point of view of energy consumption for the processes of mixing and electrical heating of the raw material. Key words: Reynolds criterion, heat transfer coefficient, heat transfer coefficient, specific density of raw materials, anaerobic digestion, mixing
Experimental study of heat and mass transfer in solid dispersed materials during vapor-depression drying
The intensity of technological processes involving dispersed materials is most often limited by the speed of internal mass transfer. The vapor-depression drying method, developed by scientists of the Institute of Thermal Physics of the National Academy of Sciences of Ukraine, allows for the intensification of internal moisture transfer and thus creates the prerequisites for accelerating the drying process. The vapor-depression drying process has been considered in detail in the literature for the case of drying a capillary-porous body - sheet plaster. The purpose of this study is to consider the effect of a vapor-permeable shell on the intensification of internal mass transfer during the drying of a capillary-porous colloidal body - viscose fiber. In experimental studies, ordinary knitted shells and shells with increased density, as well as cloth and paper shells were used. The absence of a clearly defined period of constant drying speed was recorded, which indicates a low intensity of moisture transfer in the material. The highest values of the drying speed are achieved when using a single knitted shell, the lowest - when dewatering the fiber in a cloth shell. The obtained experimental data can be used to develop effective methods for controlling the drying processes of solid dispersed bodies. Key words: vapor-depression drying, solid dispersed bodies, vapor-permeable shell, drying rate
Experimental study of the operation of a Stirling engine with a solar concentrator and an additional energy source
The efficiency of solar energy is limited by the natural variability of solar radiation levels. The Stirling engine is a promising solution for solar energy systems, especially when using concentrators, such as a Fresnel lens. The main obstacle to the widespread implementation of such systems is their dependence on the stability of solar radiation. The purpose of the research is to create an experimental stand and methodology to determine the feasibility of using an additional energy source (electric heater) to prevent the shutdown of the Stirling engine, which uses concentrated solar radiation using a Fresnel lens as the main source of heat. The paper presents an experimental study of the Stirling engine, which includes the study of the effect of variable insolation and the assessment of the efficiency of using an electric heater as an additional energy source (AES) to improve system stability. A series of experiments was conducted with different durations of insolation interruption (20, 40 and 60 s). The results confirmed the ability of the AES to prevent engine shutdown and increase the total energy produced by 47 %, 90 % and 130 % for the respective intervals. Key words: Stirling engine, Fresnel lens, additional energy source, power stabilization, solar energy, experimental stand
Research on the efficiency of using solar tracker in urbanized conditions
In the context of rising energy prices and the need for energy independence, the development of renewable energy sources, in particular solar, is becoming particularly relevant. Solar power plants (SPPs) on the roofs of multi-story buildings are a promising solution for urban environments, where the area for ground-based installations is limited. To maximize electricity production from a limited area, it is critical to use technologies that increase system efficiency. Solar trackers, which automatically orient photovoltaic modules perpendicular to the sun's rays, are one of the most effective tools for achieving this goal. The main objective of this study is to analyze the technical and economic feasibility of implementing different types of solar trackers for a solar power plant located on the roof of a typical nine-story building. The objectives are: • to conduct a comparative analysis of single-axis (HSAT, VSAT, tilted axis) and dual-axis trackers; performing technical generation calculations and assessing the impact of key factors such as spatial constraints, shading and temperature; • assessing economic feasibility, taking into account initial investments and payback; • providing sound recommendations for two specific locations in Ukraine: Zaporizhia (south) and Ivano-Frankivsk (west). Key words: photovoltaic module, solar tracker, single-axis trackers, temperature, insolation, multi-storey building