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  Problemele energeticii regionale

E-Journal N4(56) 2022



1 Evaluation of the Idle time of Single-Chain and Double-Chain Overhead Power Lines of 6–10 kV by Methods of Queuing Theory
Authors: Basmanov V.G., Kholmanskikh V.M. Vyatka State University Kirov, Russian Federation
  Abstract: The aim of this work is to substantiate the idle time evaluation of the overhead power line (OPL) according to the reliability indicators of its main elements using the probability value of the overhead power line availability factor. Statistical studies of the 17 OPL were performed to achieve this goal. The results of the statistical data processing made it possible to consider over-head lines as objects of a multiple action, and their failure and recovery flows as the primitive Poissonian flows. The calculation of the Wilcoxon and Pearson criteria confirmed the uniformi-ty of the statistical material both in terms of failure times and recovery time for all 17 studied OPL, which allowed combining the uniform statistical data into two representative samples, ac-cording to failures and recoveries, for the generalized district OPL and calculate its reliability indicators. The most significant result is the justification of applying queuing theory methods to evaluate the idle time of 6–10 kV single-chain and double-chain of overhead lines. The signifi-cance of the results obtained consists in that a simple engineering method is proposed to evalu-ate the availability factor of the overhead power line according to the reliability indicators of its main elements, which allows predicting the idle time of the overhead line for the upcoming cal-endar year of its operation. The newly obtained availability factors of the main overhead line elements can be used in the overhead power lines’ design.
  Keywords: overhead power lines, technical availability factor, comprehensive reliability indicators, idle time, graph of states, queuing equations.
2 Online Identification of Synchronous Generator Electromechanical Parameters for Intelligent Control Problems
Authors: Frolov M.Yu, Stepanovich R. Yu, Lizalek N.N., Dulov I.V. Novosibirsk State Technical University Novosibirsk, Russian Federation
  Abstract: The control system intelligence is determined by the ability to adapt to changing circuit-mode parameters. This approach is especially relevant for emergency automation, because the emer-gency depends on the huge number of factors. In addition, an accident can develop in cascade, causing uncontrolled and multiple changes in the grid topology and mode parameters. The for-mation of the control actions volume of emergency automatics is carried out on the basis of the computing of the mode on mathematical models of electrical grids, the accuracy of which de-termines the adequacy of the actions of automation, so the models verifying problem arises, in-cluding electromechanical parameters determining of the grid elements. The aim of the research is to develop methods for parameter identification of synchronous generators. The paper pre-sents two methods for identifying the synchronous generator constant inertia and the method for identifying the synchronous inductive resistance. The research of the proposed methods was carried out on the digital model assembled in MatLab Simulink, where the 200 MVA 13.8 kV generator was simulated. In addition, the research was performed using the physical electrody-namic model. The parameters of the generator 3000 VA 230 V were determined. The results of parameters determining by the classical methods of open-circuit and short-circuit are presented. The significance of these methods is that the generator is connected to the grid and is in an op-eration mode. This will make possible to form and refine the model online in accordance with the circuit-mode situation, which will increase the control actions adequacy.
  Keywords: parameter identification, rotor inertia constant, synchronous inductive reactance, synchronous generator, intelligent control, least square method.
3 Spectral Methods for Monitoring Transformer Equipment State of Paper Insulation
Authors: Kozlov V.K., Kurakina O.E., Sabitov A.H., Nigmatullina G. F., Salyakhutdinov R. A. Kazan State Power Engineering University, Kazan, Russian Federation
  Abstract: The insulation of an oil-filled transformer is based on materials of organic origin - oil and wood pulp. The state of insulation is a key factor in the reliable operation of a power equipment, and much attention is paid to the insulation state assessment by researchers. To assess the cellulose insulation state, indicators such as the degree of polymerization and paper moisture are deter-mined. The existing methods for determining the moisture content and the degree of polymeriza-tion of a paper insulation have disadvantages, as they require a complex process of sampling the insulation, which is a time-consuming operation. The purpose of the work is to develop new methods for determining the moisture content and the degree of polymerization of the paper in-sulation of a power transformer. This goal is achieved by obtaining the reflection spectra of the paper insulation samples and constructing two correlation lines to determine the degree of polymerization and humidity. The most significant result of the article is the establishment of the dependence of the reflection coefficient of the paper on the concentration of water exceeding 4% and the position of the minimum in the reflection spectrum of paper insulation on the degree of polymerization. The significance of the obtained results lies in the fact that the optical method for determining the moisture content and the degree of polymerization of paper insulation using the constructed correlation lines is highly accurate and does not require the use of additional re-agents and complex calculations.
  Keywords: cellulose insulation, spectroscopy, moisture content, degree of polymerization.
4 Minimization Electric Losses in Transistor DC Drives
Authors: Kovalov V.1, Kovalova Yu.2 1 National Technical University of Ukraine "Kharkiv Politechnical Institut" 2 O.M. Beketov National University of Urban Economy in Kharkiv Kharkiv, Ukraine
  Abstract: This work is devoted to develop the algorithm for determining the optimal switching frequency of a transistor pulse-width converter (PWM) to minimize the total electric losses in a DC drive. Electric losses in the armature winding and in the PWM transistors are divided into two compo-nents: static, from the direct current component, and dynamic. The latter include losses in the armature winding from the harmonic components of the current and losses in transistors from transient switching currents. Since the dynamic losses in transistors increase with increasing frequency, and in the armature winding they decrease from current harmonics, there is an optimal switching frequency value at which the total dynamic losses in the PWM drive will be minimal. This aim is achieved by solving the problem of determining the analytical dependence of dynamic electric losses in the armature winding on the PWM switching frequency and computer simulation of a transistor DC drive. As a result of the research, an analytical expression was obtained for calculating the relative dynamic electric losses in the armature winding with polyharmonic power supply. An algorithm was proposed for determining the optimal switching frequency of the PWM: 1) on computer models of the DC motor and PWM, the dependences of dynamic electrical losses on the switching frequency were determined; 2) the graph was built showing the dependence of the total dynamic electric losses, on which the point was determined of minimum losses, which corresponds to the optimal value of the switching frequency. The novelty of the work was that the theory of electric losses in the armature windings with polyharmonic power was further developed.
  Keywords: transistor electric drive, switching frequency of transistors, electrical losses, current ripple factor, computer models.
5 Perspective Ways of Energy-Efficient Modernization of Heat Supply Systems Based on Heat Pump Technologies
Authors: Petrash V. D., Baryshev V. P., Shevchenko L. F., Geraskina E. A., Danichenko N. V. Odessa State Academy of Civil Engineering and Architecture Odessa, Ukraine
  Abstract: This work is devoted to determination a generalized indicator for a preliminary assessment of the conditions for increasing the efficiency of modernized systems of centralized and decentral-ized heat supply using heat pump technologies. This goal is achieved through a critical analysis of the results of the actual state of pipelines and equipment, known approaches to the recon-struction of heat supply systems and the establishment of a generalized indicator of the condi-tions for increasing the efficiency of using primary fuel energy. This made it possible to formu-late a generalized approach to the modernization of heat supply systems with the introduction of heat pump technologies. The most important result of the study is the established generalized dependence of the assessment of the increase in the efficiency of heat supply systems on the initial conditions of regime parameters with the rationale for the feasibility of modernizing dis-trict heating systems based on the diverse phased introduction of heat pump technologies at all stages: generation, transportation, distribution, conversion and controlled consumption of heat by subscriber system. The significance of the obtained research results lies in the fact that the proposed approach to the modernization of centralized and decentralized heat supply systems based on heat pump installations with real conversion factors in the range (3--5) with an increase in the available heat potential is to increase the efficiency and expand the use of heat from primary fuel with its savings of 1-2.7 times.
  Keywords: heat pump, heat generator, heat recovery, heat supply, energy efficiency, system modernization, heat flows, conversion factor.
6 Modeling of Object Monitoring Using 3D Cellular Automata
Authors: Zakharchenko I., Tristan A., Chornogor N., Berdnik P., Kalashnyk G., Timochko A., Zalevskii A., Dmitriiev O. Kharkiv National Air Force University named after Ivan Kozhedub Kharkiv, Ukraine
  Abstract: The purpose of this work is to develop a formal model for describing the properties of the environment for the functioning of unmanned aerial vehicles and to increase the speed of calculating the trajectory of their flight when monitoring critical infrastructure objects based on the mathematical apparatus of 3D cellular automata. This goal is achieved by solving the following problems: developing a method for describing the operating environment of unmanned aerial vehicles based on 3D cellular automata, developing a method for calculating the flight path of unmanned aerial vehicles. The construction of formal models is based on the apparatus of 3D cellular automata. The most significant results are a formalized description of the space, properties of zones and objects that restrict movement, as well as the development of a method for modeling the flight of an unmanned aerial vehicle in space when solving the monitoring problem, which will increase the speed of calculating the flight path. The significance of the results obtained lies in solving the complex problem of calculating the trajectory of movement of unmanned aerial vehicles for monitoring critical infrastructure objects using the apparatus of 3D cellular automata. The conducted studies have shown the effectiveness of using 3D - cellular automata to solve the problems of finding flight paths when monitoring critical infrastructure objects in various conditions. The proposed approach to the implementation of cellular automata will allow creating an effective monitoring system.
  Keywords: monitoring system, UAV, power system, cellular automaton, optimization, clustering.
7 The Problem of Choosing a Steganographic Container in Conditions of Attacks against an Embedded Message
Authors: Bobok I., Kobozieva A., Sokalsky S. Odessа Polytechnic National University Odessa, Ukraine
  Abstract: Steganography is the perspective area of information security. The reliability of the stegano- graphic system, its stability is affected by the carrier – a container, which is considered in the paper as a digital image. The aim of the work is to increase the resistance of a steganographic system to attacks against an embedded message by developing a method for choosing a contain-er from a finite set of available digital images that ensures the transmitted message the minimum (close to the minimum) possible sensitivity of the generated steganographic message to disturb-ing influences under consideration with the selected steganographic algorithm. The goal was achieved using a theoretical study of perturbations of the formal parameters of the container ma-trix, as a result of steganographic transformation and active attacks, which made it possible to introduce a new formal representation for information protected from perturbing influence E, as the difference of low-rank approximations of container matrices and steganographic messages. The most important result of the work is the development of a container selection method ready for practical implementation. The efficiency of the developed method exceeds the efficiency of analogs, it remains high, regardless of the used steganographic method, which allows increasing the overall resistance of the steganographic system to attacks against the embedded message. The significance of the obtained result lies in the use of the developed method of increasing the stability of the steganographic system to attacks against the embedded message.
  Keywords: steganographic method, digital message, choice of container, resistance of the stegano system, singular value, singular vector.
8 Automatic Control System for Shell and Coil Heat Exchanger with Variable Heat Exchange Surface Area
Authors: 1Sit M.L., 1Juravleov A.A., 2Patsiuk V.I., 1Timchenko D.V., 1Institute of Power Engineering of Moldova, Kishinau, Republic of Moldova 2Moldovan State University, Kishinau, Republic of Moldova
  Abstract: The work is devoted to the temperature control system at the outlet of a shell and coil heat exchanger with a variable heat exchange area, subjected to a change in the surface area by changing the level of the heated coolant in the heat exchanger. The aim of the study is to develop a model for the process of changing the heat exchange surface area and a temperature control system at the outlet of such a heat exchanger when the level of the liquid changes. The set goal is achieved by solving the following problems: development of discretization schemes for a system of differential equations describing the dynamics of the heat exchanger, development of an automatic control system for the temperature at the heat exchanger outlet by changing the heat exchange surface area of the heat exchanger and assessing the possibility of compensating disturbances. The most significant results are: discretization schemes for equations of dynamics of a heat exchanger with a variable heat exchange surface area, the use of which makes it possible to improve the accuracy of modeling and in the substantiation of the structure and choice of parameters of the controller. The paper presents two discretization schemes for differential equations of the dynamics of heat exchanger: a scheme using the method of lines and the method of running counting. It has been established that when using a scheme using two pumps to level control, the dynamics of the object depends on the sign of the derivative of the control signal.
  Keywords: heat exchanger, variable heat transfer surface, control system, mathematic model, heat pump.
10 Data Processing Technology for the Forecasting of the Water Inflow into a Reservoir with the Use of Earth Remote Sensing and the Network of Meteorological and Hydrological Posts
Authors: Eroshenko S.A.1, Matrenin P.V.1,2, Khalyasmaa A.I.1, Klimenko D.E.1, Sidorova A.V.2 1Ural Federal University, Yekaterinburg, Russian Federation 2Novosibirsk State Technical University, Novosibirsk, Russian Federation
  Abstract: Management of the hydropower plants requires the economically efficient use of water resources based on the forecasts and simulation models of the hydropower plant and the reservoir. There are various data sources for the water inflow forecasting: meteorological and hydrological posts, Earth remote sensing. However, the problem arises of combining the specified heterogeneous data for aggregated processing with the use of machine learning methods. The research goal is to design an architecture of a system for collecting and processing the data from various sources to operational forecast of the water inflow and the reservoir water-level. It was achieved by analyzing and selecting the sources and methods for the use of Earth remote sensing data; observing the main principles of hydrological modeling; assessing the availability of the different data; analyzing the ways of increasing the observability of the hydrological objects by installing additional meteorological and hydrological posts; and designing a technology for the automatic data collection and processing. The most significant results are developed architecture of the data collection and processing system and the technology for aggregating heterogeneous data with the use of machine learning methods. It is aimed to reduce the error of short-term forecasting of the water inflow to the reservoir. The significance of the results lies in the fact that the proposed technology was offered and justified for a real hydropower plant; and it can improve the water resources management efficiency: increase the energy generation, minimize the sterile spills, increase the flood forecasting horizon and reduce the risk of flooding during the spring high water.
  Keywords: architecture of the information system, data collection and processing, Earth remote sensing, hydrological posts, meteorological posts, hydropower plant, inflow forecasting, reservoir.
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