Visnyk of Vinnytsia Politechnical Institute

Method of Forced Atmospheric Circulation in a Large City with Low Temperature Inversion

M. V. Katkov — 2025-02-27

The data of the given research propose a new method for smog elimination in cities with temperature inversion of ground atmospheric air. This method based on device creates forced turbulence of air atmospheric volumes with different pollution levels. The device uses a two-circuit turbojet engine that captures and passes through itself the polluted air from lower atmospheric layer. The device moves a mixture of polluted air and combustion products to a height above the inversion layer, where, due to dilution in a large volume of cleaner air, the concentration of pollutants and fuel combustion products decreases to an acceptable level. The volume of the displaced polluted air is filled with clean atmospheric air. The device relates to the field of creating forced turbulence of air flows and can be used in the absence of natural resources for self-purification of atmospheric air, in cities with temperature inversion of atmospheric air near the surface. This is important from the point of view of increasing environmental safety, especially for large megacities, where polluted air from motor vehicles and the activities of powerful enterprises, in particular municipal and thermal power plants, prevails, and the high concentration of high-rise buildings (skyscrapers) interferes with normal atmospheric flows and access to fresh air for their residents. Therefore, the developed method and the corresponding device allow for effective forced air circulation of atmospheric air in large cities with a low temperature inversion layer.

Resource Potential of Nonserviceable Pesticides

V. A Ishchenko — 2025-02-27

Ukraine has accumulated a significant amount of nonserviceable pesticides, in the process of their disposal the possibility of extracting valuable resources should be taken into consideration. At the same time, statistical data on the volume of non-serviceable pesticides formation are fragmented and incomplete. The total weight of pesticides used in Ukraine can be estimated at approximately 105 thousands t/year: herbicides — 60 000 t/year, fungicides — 17000 t/year, insecticides — 10000 t/year, others — 18000 t/year. Among the pesticides used in Ukraine, the largest share is accounted for by those based on the active substance acetochlor (13% of all active substances). The authors estimate that about 4—5 tons of pesticides end up in waste. Besides, some unknown amount of waste pesticides is formed in households. The article analyzes two main ways of resource recovery from waste pesticides: obtaining a useful product through chemical/ physicochemical transformations; using the products of pesticide incineration. Chemical transformations using active oxidation, photolysis, etc. allow obtaining valuable chemical products, for example, cyanuric acid (from nitrogen-containing pesticides), solvents (acetone, ethyl alcohol, ethyl acetate, isopropyl alcohol), chemical raw materials for the fertilizers production (from phosphate-containing pesticides). Some waste pesticides can be used as plant growth stimulants. The products of chemical decomposition of acetochlor, dimethachlor, propisochlor and other similar pesticides may have further application, for example, for alcohols production. However, the use of chemical methods requires the ability to accurately identify waste pesticides. Those pesticides accumulated over the past years are hardly possible to identify and the only way is the incineration. This method produces ash that can be used for road construction or as a foundation filler. This method is simpler, more affordable, and does not require pesticide separation.

Capture of Carbon Dioxide in a Rotated Packed Bed with Wire Mesh Packing

O. A. Zabolotnyi — 2025-02-27

The calculation of mass transfer efficiency in a centrifugal apparatus with a wire mesh packing has been performed, taking into account the complex interaction of structural, hydrodynamic, and physicochemical parameters of the process. In this study, the developed methodology is based on empirical equations that describe the mechanisms of mass transfer between the gas and liquid phases under conditions of intense turbulent flow. A distinctive feature of the calculations is the application of similarity criteria, such as Reynolds, Weber, and Galileo numbers, which make it possible to account for the complex influence of parameters related to the apparatus design, properties of the working media, and hydrodynamic conditions.

The modeling is based on equations for determining the mass transfer coefficient, which consider the influence of such structural parameters of the apparatus as the radius of the packing, the height of the wire mesh layer, and the cell size of the mesh. Hydrodynamic characteristics, including the flow velocity of the gas and liquid, the density and viscosity of both phases, as well as the surface tension of the liquid, were also taken into account. These parameters are critical to achieving a high degree of phase contact and enhancing mass transfer efficiency.

The calculations made it possible to determine the mass transfer coefficient as a function of the gas and liquid flow rates, their thermophysical properties, and the geometric characteristics of the apparatus design. It was assumed that the final concentration of carbon dioxide at the outlet of the apparatus equals zero, allowing for the modeling of ideal conditions to evaluate the maximum efficiency of the process.

The results of the study enabled not only the prediction of mass transfer process efficiency under various operating conditions but also the optimization of the apparatus design. This made it possible to identify the parameters that ensure the most effective separation of gas and liquid phases. In particular, the influence of changes in the height of the wire mesh packing, the apparatus diameter, and the flow rates of the gas and liquid on efficiency indicators was assessed.

Thus, the calculations, carried out, enabled to evaluate the relationship between the geometric parameters of the packing, flow velocity, and mass transfer efficiency. This has practical significance for the industrial implementation of centrifugal apparatuses with wire mesh packing in various fields. It is especially relevant for areas such as gas purification from harmful components, the chemical and petrochemical industries, where intensive and stable mass transfer is required under compact operating conditions.

Utilization of Sewage Sludge of Leather Industry. Energy Prospects

О. R. Mokrousova — 2025-02-27

The growing amount of tannery sludge generated by leather processing often undergoes uncontrolled landfilling, or open dumping, releasing a significant volume of harmful pollutants, including carcinogenic chromium (Cr) into the air, water, and soil. Therefore, sustainable TS management through advanced valorization technologies becomes vital to align with the Sustainable Development Goals (SDGs) and mitigate the adverse environmental, health, and social impacts.

Tannery sludge, as biomass, can be considered a renewable energy source for bioenergy generation which could be a viable solution for meeting contemporary environmental standards and expediting the transition towards a circular economy.

Tannery sludge is an available resource that has been successfully used in anaerobic digestion, biogas, biodiesel, and industrial oil production. We offered a critical review of tannery sludge valorization technologies towards energy recovery.

Many studies have shown that typical anaerobic digestion of tannery sludge requires a long period with low utilization efficiency and biogas yield. Chromium leaching is a major problem in composting and anaerobic digestion of this waste.

Overall, the use of tannery sludge is proving to be a very promising alternative for biodiesel production.

We also explored the environmental hazards of chrome-containing tannery sludge. Tannery sludge valorization is sensitive and critical due to the potential risk of transforming Cr(III) to Cr(VI) during the process. Therefore, there exists an urgent need for considering efficient and holistic tannery sludge valorization technologies in the design, implementation, and operations phases to avoid any environmental and health hazards.

Method of Determination of the Shortest Path of Mobile Robotic Platform in the Conditions of Limited Resources

O. M. Pavliuk — 2025-02-27

With the transition to Industry 5.0, mobile robotic platforms (MRPs) have become an important element of industrial automation, replacing outdated conveyors. They optimize the transportation of materials at industrial enterprises, integrate with control systems and adapt to changing conditions. The authors focus on their navigation in dynamic environments, avoiding obstacles when interacting with people in conditions of limited resources. The paper analyzes the limitations of existing approaches to route planning for MRPs, in particular the A*, D*, DLite, M algorithms in dynamic environments. Special attention is paid to the optimization of algorithms using federated learning, introducing artificial intelligence to increase productivity.

The authors proposed a method for determining the shortest route for AGV, which is based on classical algorithms for finding the optimal route in conditions of static and dynamic obstacles, taking into account limited resources, in particular the remaining battery charge and the time to complete the task. Stationary obstacles include walls and fixed workplaces of personnel, and dynamic obstacles are classified as living (industrial personnel) and inanimate (other MRPs or unpredictable objects such as boxes). Federated learning is used to predict the voltage drop of MRP batteries taking into account the individual characteristics of the platforms. The developed method involves dividing the route map into a uniform grid, constructing obstacle matrices, predicting battery voltage and calculating the optimal route using the A*, D*, DLite, M algorithms. The effectiveness of the method is evaluated by the following parameters: route length, number of cells passed, execution time, remaining battery charge. The results of the method are presented on the example of the AGV Formica 1 route, AIUT, Gliwice, Poland.

The D* algorithm underlying the developed method is the most efficient in terms of execution time, number of cells passed, and battery conservation, which makes it optimal for dynamic conditions. The DLite and M algorithms also show good performance in static conditions, with lower resource consumption. A*, although it finds the optimal path, is the slowest and less efficient under limited resources. Thus, for dynamic environments, D* is the best choice, while DLite and M are good options for stable conditions.

Using Machine Learning to Locate People Indoors

A. I. Topolskiy — 2025-02-27

The article investigates the problem of automated data processing to record the presence of students in classes. It is proposed to use machine learning methods, since they allow predicting the location of students in the premises even in the presence of anomalies in the data. The solution to this problem will help to increase the efficiency of the educational process and reduce dependence on traditional methods of recording presence, which require time and human resources.

Experiments were conducted using various machine learning methods for regression and classification tasks. Prediction accuracy was used as a measure to compare different methods.

Among the regression methods, the following were considered: SVR, LinearSVR, NuSVR, PLSRegression, KernelRidge, RidgeCV, BayesianRidge, DecisionTreeRegressor, and ExtraTreeRegressor. The best accuracy was obtained by DecisionTreeRegressor, KernelRidgeRegression and ExtraTreeRegressor methods — 92.5, 93.9 and 95.5 %, respectively. However, regression methods require continuous data, such as user coordinates, which limits their use in environments where technical means do not allow obtaining such data.

As an alternative, classification methods were considered, namely: SVC, KNeighborsClassifier, DecisionTreeClassifier and RandomForestClassifier. The initial results showed lower accuracy compared to regression methods, which was due to the lack of representativeness of the training data. To solve this problem, a step-by-step algorithm was applied, which gradually predicts the building, floor and specific room. This algorithm led to a significant improvement in accuracy, with the best result being achieved by the RandomForestClassifier method — 94.3 %.

It was concluded that the choice of a machine learning method depends on the technical means used. If they allow you to obtain continuous data, such as coordinates, it is optimal to use the ExtraTreeRegressor, DecisionTreeRegressor, or KernelRidgeRegression regression methods. If continuous data cannot be obtained, it is optimal to use the RandomForestClassifier classification method with the proposed step-by-step algorithm.

Modified Algorithm for Decoding Convolutional Turbo-Codes

Yu. Yu. Ivanov — 2025-02-27

At the current stage of development of the theory of error-correcting codes, a turbo-code is a promising technique, which provides the necessary error-correcting characteristics for various data transmission systems. It represents a powerful class of error-correcting codes with a unique codec structure, capable of operating effectively at high speeds in channels with low useful energy, almost completely using channel capacity by the principles of K. Shannon. The process of turbo-decoding using specialized iterative probabilistic algorithms requires significant computational resources, which can become a limitation for real digital data transmission systems. The article proposes a suboptimal modification of the turbo-decoding algorithm based on the maximum a posteriori likelihood in an iterative form, which uses the approximation of the correction function during the calculation of the correlation metrics of the trellis-diagram transitions of a recursive systematic convolutional code. The proposed function outperforms analogues in the base interval of values by statistical indicators.

The algorithm's efficiency was demonstrated during computer simulation of the work process of a digital data transmission system on random frames and multimedia data. The experimental functional dependence of the bit error rate on the signal/noise ratio in the communication channel was found and analyzed. It was determined that the modified algorithm outperforms several analogues in the terms of energy gain in communication channels with a high level of noise component, its efficiency is as close as possible to the basic algorithm, but has lower computational complexity. The article can be useful for engineers and designers of data transmission systems since it allows more efficient analysis and synthesis of turbo-codes depending on the given tasks.

Modeling of Adaptive Knowledge Testing: Efficiency Threshold, Task Complexity and Completion Time

O. F. Shevchuk — 2025-02-27

A comprehensive informational and analytical analysis has been conducted to evaluate the feasibility of implementing adaptive computer-based knowledge testing for specific academic disciplines in educational institutions. The shortcomings of the traditional approach, which imposes fixed time constraints for test completion without considering the individual characteristics of learners and potentially causing negative reactions among test participants, have been identified. Alternatively, an integral assessment approach is proposed, accounting for both task complexity and task completion time. An adaptive algorithm has been developed based on the efficiency threshold q, which determines the adjustment of the difficulty level for subsequent tasks depending on the integral evaluation result of the previous task. Simulation modeling was carried out using Python to verify the effectiveness of the proposed approach. A test dataset comprising tasks of three complexity levels was created, with completion times modeled according to the normal distribution. The analysis revealed that significant differences in task difficulty levels necessitate establishing separate efficiency thresholds for each category of questions, while minor differences allow for a single threshold for all test tasks. Parameter tuning for the integral assessment was performed within the test dataset, and the effectiveness of the proposed method was examined. It was noted that the obtained coefficients of the integral evaluation could serve as baseline values during the initial implementation phase of the system, with further optimization based on model training results during pilot testing. The described methodology demonstrates flexibility and ease of implementation, enabling parameter customization and effective adaptation to both the individual characteristics of learners and the specific requirements of individual disciplines. Furthermore, recording task completion times can serve as an additional tool for assessing the quality of test items.

Models and Metrics for Information Technologies Based on Visual Ternary Comparisons

V. V. Kolodnyi — 2025-02-27

A new tool for identifying preferences in conditions of target and criterion uncertainty is proposed — lifts of preferences in the form of three sliders with adjustable discreteness. By moving these sliders on the screen of a laptop, tablet, or mobile phone, decision makers apply quick intuitive thinking and visualize their preferences for three alternatives. Visual, numerical, mathematical and symbolic models of visual ternary comparisons are considered and researched. New metrics are proposed for the numerical interpretation of visual ternary comparisons in order to more accurately and reliably calculate the resultant (overall or summarizing) cardinal rankings: the additive metric of sliders height differences and the multiplicative Z-metric. The joint application of both of these metrics showed the coincidence of the ordinal rankings and the closeness of the corresponding values of the resulting normalized and centered cardinal rankings. New metrics are proposed for the logical interpretation of visual ternary comparisons in order to identify the characteristic features of decision-makers (passivity, extremity of assessments, inconsistency of judgments and incompetence). All cases of the generation of binary three-level comparisons were considered and analyzed, and the concept of distance between them was defined, which can be considered a measure of the intransitivity of preferences, that is, the inconsistency of judgments of decision-makers. A new adaptive metric for distinguishing relations of preference and strong preference is proposed, which takes into account individual features of visual ternary comparisons performed by decision-makers. An example of practical implementation of the proposed models and metrics is considered. It is planned to further research the toolkit for identifying preferences based on visual ternary comparisons and improving the information technologies developed by the authors for effective, reliable and visual organization of collective online expertise.

Application of Optical Fiber Sensors for Temperature Control in Medical Equipment

W. Wojcik — 2025-02-27

The paper presents the results of determining the influence of temperature on the optical parameters of an inclined Bragg grating and the analysis of the possibility of its use as a temperature sensor for monitoring the state of biomedical equipment. Methods for determining the thermal modes of the element base are the basis for analytical calculation of reliability indicators of biomedical equipment related to the temperatures of individual elements of the electronic structure. Currently, optical methods of radiation control are widely used in various fields of science and technology, due to the fact that it is possible to change the following parameters of a light wave: amplitude, frequency, phase, polarization and direction of propagation.

Optical devices such as modulators, deflectors and filters are characterized by high speed, low control power, simplicity of design and high reliability. These advantages have ensured their wide application not only in laser physics, but also in measurement technology, ecology, medicine, military sphere, etc. Today, the influence of temperature on the optical parameters of inclined Bragg gratings has been studied practically insufficiently.

The work investigates a temperature sensor based on the use of an inclined Bragg grating, where the spectral characteristics and parameters of which change under the influence of temperature. Mathematical models for determining the parameters of the thermal field of elements of biomedical equipment are proposed. Analytical solutions for calculating temperature determination based on the use of Bragg gratings are obtained, which take into account heat removal from all surfaces of the elements.

The work, in terms of the relevance of the problem and the ways of its implementation, corresponds to modern trends in world science and technology. It was concluded that the change in the length of the Bragg wavelength with temperature gives a linear dependence. There is a different sensitivity in each temperature range, therefore the resulting value was obtained by calculating the average value for the entire temperature range for each Bragg grating.

Method for Synthesizing a Benchmark to Evaluate the Robust Resilience of Large Language Models to Disinformation and Factual Manipulation

S. M. Levitskyi — 2025-02-27

With the development and widespread adoption of intelligent assistants based on large language models (LLMs), testing these models by various criteria is becoming incringly important. One of the most crucial factors is their robustness against misinformation and manipulative tactics. Unstable models can pose serious risks in decision-making in the sphere of security, healthcare, and sensitive social issues. Such evaluations typically rely on benchmark tests based on labeled datasets. However, most existing benchmarks are designed for single-turn (context-free) questions, whereas LLM-based chatbots are primarily used in multi-turn conversational modes (with context). These benchmarks are highly dependent on the domain of application, meaning that instead of a single test, a method for synthesizing such tests is required.

This paper proposes a method for synthesizing benchmarks to assess the robustness of LLMs against multi-turn manipulations involving statements that are definitively known to be false. The method enables the generation of a benchmark that constructs a sequence of manipulative transformations of a false statement, eventually leading an insufficiently robust LLM to accept the misinformation as valid. The method is based on: (1) forming a set of reference, exclusively false statements from a given domain, followed by clustering and extracting typical variants; (2) creating sets of manipulation templates applicable to arbitrary statements using argumentation logic while maintaining their falsity; and (3) applying reinforcement learning to synthesize an optimal policy (strategy) for structuring sequences of fact manipulations for each type of reference false statement. The proposed robustness criterion for LLMs is the percentage of false statements correctly classified as false.

Experimental testing has confirmed the effectiveness of the proposed method. A benchmark was developed and used to evaluate the well-known LLM "Llama 3.2 3B Instruct." This model exhibited moderate (65 %) robustness against misinformation and manipulations in a single-turn (context-free) mode. However, after applying the synthesized benchmark in a multi-turn conversational mode, its robustness dropped by more than half (to 30 %). This result demonstrated the vulnerability of LLMs to more complex manipulative scenarios and validated the effectiveness of the proposed benchmark synthesis method.

Analysis of Localization Methods for Wireless Sensor Networks in Indoor IoT Environment

H. O. Pastushenko — 2025-02-27

Experimental studies and analysis of various localization methods for wireless sensor networks in the indoor environment of the Internet of Things (IoT) have been conducted. The aim of the work was to determine the effectiveness and limitations of the main localization approaches for their further application in different environments. The investigated methods included minimum Capon variance, ESPRIT algorithm, weighted subspace fitting, proximity-based positioning, and RSSI-based trilateration. The main focus was on analyzing the key characteristics of the methods, such as accuracy, energy efficiency, scalability, interference resistance, sensitivity to environmental parameters, and signal transmission range. The results showed that each of the considered methods has its own unique advantages and limitations depending on the specifics of the application. The ESPRIT algorithm, for example, provided the highest positioning accuracy and scalability, making it suitable for large and complex networks with high node density. Proximity-based positioning methods were found to be the most energy-efficient, which is a crucial factor for IoT applications with tight power constraints. The RSSI-based trilateration method demonstrated high noise immunity and stability over a wide range of conditions, including signal density variability and the presence of physical barriers in the environment. The study enabled to formulate recommendations for choosing the optimal localization method depending on the specific requirements for accuracy, power consumption, network stability, and operating environment characteristics. The results obtained are of practical value for IoT system developers, as they contribute to optimizing network performance, increasing data transmission reliability, and reducing power consumption. The findings of this study can serve as a basis for future developments and improvements of localization algorithms, ensuring their effective use in a wide range of IoT applications, such as smart buildings, industrial monitoring, logistics, and healthcare. Keywords: localization methods, wireless sensor networks, Internet of Things, localization accuracy, energy efficiency, scalability, interference resistance, sensitivity, trilateration, ESPRIT, minimum Capon variance, RSSI, proximity-based positioning, weighted subspace fitting.

Relevance of Increasing Thermal Protection of Buildings as a Result of Using Modern Windows

V. R. Serdyuk — 2025-02-27

It is shown that in the conditions of Ukraine's refusal to import natural gas since 2023, the destruction of 50 % of energy generating capacities as a result of the war of Russia against Ukraine, the issues of not only the restoration of electricity generating capacities and 10 % of destroyed housing, but also the need for thermal modernization of almost 90 % of the existing housing stock, which was built with low regulatory requirements regarding the thermal resistance of the "shell" of buildings acquire especial significance. The construction sector of the economy has large potential for reducing energy consumption.

Study of the advanced European experience in the sphere of thermal modernization of outdated housing stock by means of simultaneous insulation of walls, replacement of windows and installation of roller shutters accelerates the duration and reduces costs for insulation of facades of outdated housing. It is shown that the walls and windows of the building are responsible for the loss of almost 65 % of thermal energy by the building; the construction sector of the economy consumes 40 % of all energy carriers and is responsible for 36 % of greenhouse gas emissions.

Excessive burning of fossil fuels (coal, oil, natural gas) leads to an increase in carbon dioxide emissions and global temperature increases. Ukraine, like other countries in the world, has undertaken international obligations to reduce greenhouse gas emissions. In Ukraine, new DBN were put into effect in 2022, which provide for an increase in regulatory requirements for the thermal resistance of enclosing structures. Advanced world experience involves abandoning patchwork wall insulation, which is common in Ukraine, and switching to combined and simultaneous wall insulation, window replacement, and roller shutter installation. The advantages of such a thermal modernization technology are quite obvious.

Ukrainian window manufacturing enterprises operate on German production lines using imported components. It has been shown that over the past 20 years, Ukraine has significantly increased the production of modern windows. The export of Ukrainian windows has increased approximately 70 times, and over the past 4 years, it has tripled. In the context of adapting the regulatory framework of Ukraine in the field of construction to the requirements of EU countries, it provides for a transition to the construction of energy-efficient and passive houses, and thermal modernization of the outdated housing stock is an urgent task for Ukraine.

Thermo-Stressed State of the Dkvr-10-13 Boiler Drum when Replacement of the Standard Burner with a Jet-Niche One

A. Yu. Rachуnskyі — 2025-02-27

This work is devoted to the analysis of the thermally stressed state of the drum-separator of the DKVR-10-13 boiler type using CFD modeling using the Ansys Fluent software package. The main attention in the study was paid to studying the influence of structural and operational factors on the strength and stability of the boiler drum equipped with jet-niche burners. The analysis was carried out for two boiler operating modes: nominal load and at 60% power. The technology of stabilized combustion without pre-mixing in the burner was used. Gas distribution was carried out through round holes, perpendicular to the oxidant flow, which contributed to more efficient mixing of fuel and air. The difference between the maximum and minimum temperature of the drum surface did not exceed 30 °C, which ensures the stability of the structure. Visualization of the fields of velocity, temperature and concentrations of reaction products (in particular NOx) showed that the jet-niche technology contributes to the reduction of emissions of harmful substances and more complete combustion of fuel. The absence of flame instability or displacement of its position confirms the reliability of the combustion mode. The influence of the temperature field, internal pressure and heat flow on the strength of the drum was studied, taking into account the weakening holes. The maximum equivalent stress according to the Mises criterion was 75 MPa, which is significantly lower than the ultimate strength of the material. The maximum deformation of the drum was 1.1 mm, which does not pose a threat of destruction. The passport thickness of the drum wall (10 mm) is sufficient to ensure strength in both studied modes.

Replacing standard burners of the DKVR-10-13 boiler type with jet-niche ones contributes to: Improving the efficiency and uniformity of fuel combustion, increasing environmental performance due to reducing NO_x emissions, while ensuring the thermal strength of the drum even in variable operating modes. The results of the study are a solid basis for improving burner devices in boilers of this type and increasing their energy efficiency.

Directions for Improving the Efficiency of Logistics Systems

R. V. Melnyk — 2025-02-27

The article examines the concept of a modern logistics system, main problems that are solved to increase its efficiency and the main results that are achieved due to the optimization of the activities of key areas of logistics systems. Logistics promotes to receive products and services at the moment when they are needed by customers. It also helps in economic operations, serving the main factor of trade and commerce growth.

With the advent of the mass production system, logistics began to be recognized as a separate function. Production and transportation were previously seen as the next chain of specialized activities. The role of logistics is to provide the availability of all needed materials before each step in this chain. It is obvious that the inventory of raw materials, semi-finished products and finished products is mandatory for this chain to ensure its smooth functioning.

The logistics concept is based on a systematic approach. There is a single chain, with the flow of materials starting from the supplier, then to the factory and finally to the end user, and these activities are also performed step-by-step to satisfy the consumers at low cost. To perform successfully this work, the coordinated activity is needed. Regarding the organization, it acquires a concrete form thanks to its structure. In the past, suppliers dealing with the distribution were distributed across the structure, this led to overlapping of the work. In today's process-oriented organization, where the focus shifted from the function to the process, logistics has become an important part of the process.

Autoregressive Models of the Process of Post-War Recovery and Post-War Development of the Renewable Sources of Energy in Ukraine

B. I. Mokin — 2025-02-27

The paper [1] published the “Draft Recovery Plan for Ukraine: Energy,” developed in 2022 by the National Council for the Restoration of Ukraine. In our work [2], to align the “Draft Plan…” with the realities of the military situation, we synthesized mathematical models to represent the restoration and development processes of Ukraine's electric power industry as a whole, taking into account the stochastic nature of these processes. In our work [3], we further refined the “Draft Plan…” to address the military realities specific to the electric power industry. We developed mathematical models for the restoration and development of renewable electricity sources (RES) in Ukraine. This task was accomplished using various data, tables, and graphs characterizing RES as presented in [1]. However, we expanded the definition of RES beyond solar (SPP), wind (WPP), and biogas (BPP) power plants, as defined in [1], to include hydroelectric (HPP) and pumped storage (PSH) power plants, which were excluded from the RES category in [1]. In [3], we assumed that Ukraine's war with its aggressive neighbor would continue into 2024 and 2025, introducing a stochastic element into restoration plans—both for pre-war infrastructure and assets restored during the war. We also presumed that the restoration and development of RES would continue to exhibit stochastic characteristics over an extended period. For this reason, we proposed using second-order autoregressive models in the form of ARPKC(2,0,1), starting from the zero time point in 2023. However, in [3], the idea of employing autoregressive models was only mentioned in a general formulation. A year after completing [3], during the ongoing war between Ukraine and Russia, Ukraine’s overall electricity infrastructure and RES, in particular, suffered further destruction [4]. This necessitated the synthesis of autoregressive models in a fully operational form, suitable for use by electrical engineers in design projects. This idea is implemented in the present publication as a Python program. The foundational prerequisites for this program were initially presented in our report at the International Scientific Conference held in Kyiv in November 2024, with extended abstracts published in [5].

Measurement of 6 (10) kV Bus Sections Voltage Using Capacitive Voltage Dividers

P. M. Baran — 2025-02-27

One of the problems in an electrical network with an isolated (compensated) neutral is the selective determination of a damaged element during a single-phase earth fault. Selective operation of protections against such damage can be ensured on the basis of the analysis of zero-sequence currents, phase voltages and zero-sequence voltage of the bus section from which these feeders are powered. As operational experience has shown, selective operation of protection against single-phase earth faults in such networks can be ensured only with the use of digital devices. There are no voltage transformers at many substations and distribution points of the energy systems of Ukraine with a voltage of 6 (10) kV. Therefore, it is not possible to use modern digital protection devices at such substations, which require information about the voltages of the bus sections. In addition, at modern transformer substations, taking into account the compact placement of equipment in them, it is physically impossible to additionally install traditional electromagnetic voltage transformers. Thus, to measure high voltage, it is necessary to use other methods of voltage measurement. One of these methods of measuring high voltage is the use of capacitive voltage dividers. A physical model of high voltage measurement was developed at the Department of Electric Power Engineering and Control Systems of Lviv Polytechnic National University using capacitive voltage dividers used in voltage indication systems on bus sections of substations with a voltage of 6 (10) kV. These capacitive voltage dividers were developed by the RELSiS company. After successful testing of this system on a physical model, it was put into experimental and practical exploitation at the operating substation RP-10 of PrJSC "Lvivoblenergo". The system was used for the operation of digital protection against single-phase earth faults in grids with an isolated (compensated) neutral "Altra". In "Altra" device, analog signals (voltages of bus sections and zero-sequence currents of feeders) are converted by an analog-digital device into a digital code. After that, the signal is filtered at the digital level - the main frequency signal is selected. Fourier transformation is used for digital filtering of the signal. Zero-sequence voltage value is calculated directly in the digital device based on the sine and cosine components of the phase voltages of the Fourier transform. The positive experience of experimental and practical exploitation of capacitive voltage dividers at the operating substation of PrJSC "Lvivoblenergo" makes it possible to recommend their use at other similar substations and distribution points of electrical networks with a voltage of 6 (10) kV, where there are no traditional electromagnetic voltage transformers.

Analysis of the Efficiency of Adaptive Pulse System Functioning by the Method of Stochastic Characteristics

V. M. Slidenko — 2025-02-27

The article considers the stochastic characteristics that determine the effective range of pressure pulse generation by an adaptive pulse system to influence the bottomhole zone of an oil well from the surface in order to enhance hydrocarbon production.

For the analysis, we used dependencies that describe the processes of implosion and generation of direct water hammer, taking into account the influence of probabilistic parameters based on normal distributions of the volumetric modulus of elasticity and density of the working fluid as random variables.

The studies have established that the geometric and power parameters of the pulse generator are influential for ensuring the functioning of the adaptive pulse system, taking into account the technological parameters of the oil well, and ensuring the rational length of the implosion chamber within 0.25...1.2 m allowed the installation of an implosion pulse generator directly on the tank of the pumping unit.

The method of cleaning the bottomhole zone of a reservoir system in the process of short-term workovers with the installation of all elements of the adaptive pulse system on the surface, which ensures its reliability and ease of maintenance, is substantiated. The stochastic characteristics that affect the amplitude characteristic of the pressure pulse and the probability of its realization in the rational zone are investigated, taking into account the normal distributions of numerical characteristics for random variables — the volumetric modulus of elasticity and the density of the working fluid — reservoir water.

The range of realization of extreme power characteristics of the adaptive pulse system functioning within the standard deviation from the mathematical expectation of the values of the volumetric modulus of elasticity and the density of the working fluid is established

The presented methodology for taking into account the stochastic characteristics of the working medium for the generation of pulse processes can be useful for achieving maximum efficiency of other pulse technologies that affect the bottomhole zone of an oil well and the formation system in the filtration zone. The obtained results are important for improving technological solutions in the field of power equipment and their further implementation in industrial production.

Analysis of the Control Process of a Unified Power Quality Regulator During Rapid Voltage Changes

M. Yo. Burbelo — 2025-02-27

The article analyzes the control processes of a unified power quality conditioner (UPQC) in the event of rapid voltage changes in electrical grids. The parallel-serial and serial-parallel UPQC schemes are considered, which allow for small reactive power compensation to ensure load voltage stability. Mathematical models are presented for estimating load voltage and reactive power of compensators. Studies have shown that a parallel compensator effectively reduces reactive power consumption from the grid, while a serial compensator increases load voltage. The results obtained demonstrate the change in load voltage depending on voltage fluctuations of the power source, as well as the effect of active regulation of UPQC parameters on network voltage stability. Special attention is paid to adaptive regulation, studied within the framework of a mathematical model, which provides optimal quality of reactive power compensation and load voltage stabilization. The results obtained confirm the effectiveness of the proposed approach to UPQC control, which ensures stable system operation and increases energy efficiency of electrical networks. In addition, it is shown that the implementation of such regulators into distribution networks significantly improves their reliability and ensures compliance with modern requirements for electricity quality. The proposed control methods allow for effective adaptation of the operation of the UPQC to the conditions of the alternating mode of the electrical network. Analysis of the mathematical model confirmed that the use of the considered approaches provides voltage stability and reduced power losses. The results obtained can be the basis for further research in the field of electricity quality management.