Electrical Engineering and Power Engineering

Journal Information
ISSN / EISSN : 1607-6761 / 2521-6244
Current Publisher: Zaporizhzhia National Technical University (10.15588)
Total articles ≅ 235
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Latest articles in this journal

V.V. Kyryk, A.V. Bilyk
Electrical Engineering and Power Engineering pp 24-31; doi:10.15588/1607-6761-2020-1-3

Т.V. Tatarchuk, A.I. Havrov, S.O. Maslov
Electrical Engineering and Power Engineering pp 16-23; doi:10.15588/1607-6761-2020-1-2

S.P. Lushchin, O.I. Zolotarevskiy
Electrical Engineering and Power Engineering pp 8-15; doi:10.15588/1607-6761-2020-1-1

Electrical Engineering and Power Engineering, Volume 1, pp 21-31; doi:10.15588/1607-6761-2019-4-2

Purpose. Modification of the numerical calculation method of transients in linear electric circuits, as well as the development of a schematic model of the method, leading to ease the calculation and to increase the speed of calculation on a computer..Methodology. Polynomials approximation of functions, numeral methods of solution of integro-differential equations, matrix methods, computer programming and methods of electric circuits theory are used.Findings The improved method of transient calculation is worked out as the modification of the known one. It allows to reduce the computer modeling time of dynamic electric processes in linear electric circuits. The example of the application of the proposed method is shown. Based on the developed method, the computer program was compiled for calculating the transient in the model circuit. This example showed the reduction in CPU time of 45% compared with the use of known methodsOriginality. The approximation of the functions of currents with time by series in the Chebyshev orthogonal polynomials is used. Chebyshev polynomials possess the property of the approximation error uniformity of functions in the entire range of the argument, which distinguishes them from a number of other orthogonal functions. It is proposed to use a polynomial approximation not of the solution functions themselves, but of its derivative. This significantly reduces the approximation error of both the solution function and the derivative of the solution, which appears in the calculation method.. It is shown how, in the proposed method, integro-differential equations of state are transformed into linear algebraic equations. The schematic model of the proposed numerical calculation method is developed. The schematic model allows you to move from an electrical circuit in which processes are described by integro-differential equations to an equivalent circuit with images of currents. Images of true currents in the equivalent circuit are interpreted as direct currents. It is shown that the Kirchhoff laws are valid for current images in the equivalent circuit, which leads to the calculation of a system of algebraic equations. Such a circuit model creates convenience for an engineer performing transient calculations.Practical value. The developed method opens up the possibility of using the entire diverse apparatus of the theory of electric circuits for working with current images. Based on this, a universal software package is developed for calculating transients in electrical circuits of arbitrary
Ye.M. Vereshchaho, V.I. Kostiuchenko
Electrical Engineering and Power Engineering, Volume 1, pp 32-45; doi:10.15588/1607-6761-2019-4-3

Purpose. Assessment of the dynamic resistance of a stabilized converter based on the calculation of switching power supplies using the method of averaging state variables and using a computer. Consideration of measures to increase the output resistance and improve the parameters of the transition process, increase its stability. Consideration of the features of the pulsed power supply operation to an electric arc with a capacitance.Methodology. Classical frequency control theories and methods for the experimental determination of frequency parameters.Findings. The issues arising in the design and development of devices and power systems for the electric arc are considered - the electromagnetic compatibility of individual nodes in the power supply system, their stability, as well as the stability of the entire power supply system. A feature of the pulse voltage converter operation for a complex load is considered. The causes of the self-oscillation regime are shown. If necessary, the filter damping elements can be added to eliminate self-oscillations. The influence of external feedbacks on the dynamic properties of a pulsed voltage converter operating on an arc load is investigated. To ensure stability in the "electromagnetic interference filter- pulse voltage converter" system the output resistance of the filter should be reduced to a value lower than the input resistance of the converter. The results of the complex input resistance calculation of a pulse voltage converter can be used to analyze the stability of the power supply system with the input filter of the radio noise. Additional feedback on the voltage across the arc leads to a significant increase in the output impedance of the converter and to smoothing its frequency response (the absence of a resonance maximum), which is highly desirable. In general, the frequency dependence of the output resistance for a dual-circuit system is more favorable than for a single-circuit in terms of dynamics.Originality. Application of new effective algorithms for calculation and spectral analysis of processes in closed nonlinear discrete systems with various types of feedbacks in the mode of their normal functioning to the new object analysis.Practical value. The presentation is constructive in nature and ends with the procedure for designing controllers using a new, full-scale control theory for objects with indefinite parameters.
A.A. Sakhno, L.S. Skrupskaya, S.V. Domoroshchyn
Electrical Engineering and Power Engineering, Volume 1, pp 56-64; doi:10.15588/1607-6761-2019-4-5

Purpose. Investigation of the nonequilibrium-compensation method for diagnosing the state of high-voltage devices with capacitor isolation, a description of the experience of using the method, finding the disadvantages and advantages of this diagnostic method, the development of improvements to the nonequilibrium-compensation method.Methodology. The study was carried out by the method of continuous monitoring under operating voltage (“online”) for bushings of a three-phase group of shunt reactors to a voltage class of 750 kV.Findings. As a result of the study, the authors developed an improved mathematical model for the nonequilibrium-compensation method, which takes into account the influence of the operating voltage, and received the final formula for determining the unbalance current, which can significantly increase the reliability of the diagnosis. The improved model is different in that it takes into account additional parameters - a working three-phase voltage, under the influence of which is the insulation of electrical devices. The values of the phase and amplitude of the unbalance current obtained using the model will not depend on the network operating modes, such as asymmetry, for example, and, accordingly, there is no need to set the overshot alarm settings and equipment shutdowns, unlike the “classical” method, since the parameters change unbalance current will be caused only by changes in active losses in isolation or partial breakdown of the insulation design of the device. Originality. The authors developed an advanced mathematical model for the diagnosis of high voltage apparatus with capacitor isolation under operating voltage. The result of the calculation of the new model does not depend on the effects of operating voltage (such as asymmetries of amplitudes and interphase angles).Practical value. The obtained model can be used in the production of systems and devices for continuous diagnostics (monitoring) of the main insulation of high-voltage bushings at voltage classes of 110 - 750 kV.
Electrical Engineering and Power Engineering, Volume 1, pp 46-55; doi:10.15588/1607-6761-2019-4-4

Purpose. In the implementation of investment projects, the process of industrial production, associated with the choice of the optimal supplier, customer, business partner; determining the best quality of products, minimizing the cost of purchasing and delivering material resources, etc.. This article analyzes the information technology of a software product to automate the decision support process in the financial investment activity of a metallurgical enterprise..Methodology. To solve the optimization problems, the following methods were applied: methods of studying the functions of classical analysis; indefinite Lagrange multipliers; variational calculus; dynamic programming; maximum principle; linear programming; nonlinear programming.. Findings The designed system, helping to make the most effective, comprehensive solution, can reduce the intellectual burden on the decision maker, minimize the number of routine operations and complex mathematical and economic calculations and, as a consequence, significantly reduce the time for decision. The advantage of the considered software product is that it is able to solve simultaneously two urgent tasks for today - to form the optimal portfolio of securities and to choose the optimal supplier of resources. Thus, it is convenient for metallurgical enterprises and will reduce the cost of purchasing software.Originality. This software product has no analogues at the moment, it is able to solve two current problems for today simultaneously - to form an optimal portfolio of securities, and to choose the optimal supplier, which will reduce the cost of purchasing materials and use these funds for the implementation of energy conservation projects at metallurgical enterprisesPractical value. The calculation method offered by the choice of the optimal supplier is universal and acceptable for the evaluation of enterprises in terms of different characteristics: the proposed methodology is based on a comprehensive, multidimensional approach to the evaluation of such complex phenomenon as the financial and economic activity of the enterprise; a flexible algorithm is used to obtain the valuation of enterprises, which realizes the possibilities of a mathematical model of comparatively-complex evaluation of the enterprise activity; the algorithm of calculations allows to move away from formation of conditional reference enterprise; the calculation is based on determining the interval of variation of features; the technique is based on bringing the numerical parameters to a single equivalent, which in this case is the approximation coefficient to the optimal value of the trait.
V. F. Ivankov, A. V. Basova
Electrical Engineering and Power Engineering, Volume 1, pp 8-20; doi:10.15588/1607-6761-2019-4-1

Purpose. Determination of resistance of a powerful power transformer to the action of geomagnetic induced currents (GIC) and structural measures for its increase, if necessary.Methodology. An analytical calculation of the magnetization current (MC) is applied, which under the action of geomagnetic induced currents is excited in addition to the rated current in the higher voltage winding. Analytical and numerical calculations of the magnetic field and the losses, and computational-empirical methods for estimation of the temperature rises are used.Findings. For a five-core transformer with a power of 630 MVA under the GIC effect, the increased losses and heating of structural elements on the cores of the magnetic system, the tank, and the increased sound level are determined.Originality. For the case of orthogonal property of the vectors of winding rated currents and the vectors of harmonic components of the peak unbalanced MC, the Joule losses are represented by the sum of the losses due to these currents using the increase factors for ohmic losses in non-magnetic and ferromagnetic structural parts, which depend on MC harmonic spectrum.Practical value. The stability of the transformer under test to the given level of GIS was confirmed, and structural measures for its increase were recommended. The tested methods can be used in the computational design, in the study of real cases of equipment operation.
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