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ELECTROENERGETICS
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Efficiency of the Compact Controlled High -Voltage Power Lines
Authors: Postolaty V.M., Bykova E.V., Suslov V.M. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova Shakaryan Y.G., Timashova L.V., Kareva S.N., Scientific centre of Federal Grid Company of Unified Energy System of Russia, Moscow, Russian Federation
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Abstract: The basic theoretical principles to create compact controlled transmission lines are analyzed in the paper. The results of technical and project elaboration of some variants of such type of power transmission lines are presented and the comparison between their technical and economic indicators with those of traditional power transmission lines and foreign analogues is made in the paper. The efficiency of compact controlled transmission lines application to form power systems and to create intersystem ties as well as distribution electric network is also stated in the paper. |
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Keywords: compact controlled power lines, single circuit and multi circuit compact lines, controlled, self-compensating transmission lines, phase-shifting devices.
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Control of Regime of Unified Interphase Power Controller by the Use of Rotary Transformer
Authors: Kalinin L.P., Zaitsev D.A., Kaloshin D.N., Golub I.V. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
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Abstract: Interphase Power Controller (IPC) has some properties of the source of the current. The use of these technical devices in electrical networks, in addition to optimization of the flow distribution, contributes to limiting of short-circuit currents and limits the level of distribution of electromechanical transients between energy systems. The increase of IPC controllability allows assigning some control function upon them and ensuring a more favorable operation of the energy system generators. We have studied a variant of such a device, which is controlled by a rotary phase-shifting transformer using the asynchronous electric machines with locked phase-wound rotor. |
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Keywords: unified interphase power controller (UIPC), rotary phase shifting transformer (RPST), power characteristics.
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A Generalized Approach to the Calculation Procedure of Distribution Network Steady-state and Transient Regime
Authors: Berzan V., Postoronca Sv., Vieru D., Tintiuc Iu. Institute of Power Engineering of the ASM Chişinău, Republic of Moldova
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Abstract: The low-voltage electrical distribution networks are characterized by ramified topology and spatial distribution of the consumers connected to the power supply. This leads to certain difficulties in calculation of such circuits even in the case of steady state mode, since even in stationary case a new separate problem must be solved each time. We have to mention that these difficulties are even more pronounced in the case of the circuit transient analysis. This paper proposes a generalized approach to calculation of steady-state and transient regimes in the branched distribution networks with RLC loads. To solve this problem we propose to use the mesh currents method, representation of the system of equations in matrix form and the Laplace transform. This gives the possibility to determine the characteristics of the current and voltage changes over time in the network and in the load. The difference between the obtained results and the known results, published in the open sources, is determined by the fact that the calculation of stationary and transient modes, is performed using the same calculations algorithm for both stationary and transient regimes. |
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Keywords: tree electric network, steady state and transient mode, mesh currents method, Laplace transforms.
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Calculation of the Electric Field and of the Parameters Of Controlled Self Compensating Power Lines 110 kV Line Using the Finite Volume Method
Authors: Patsyuk V., Berzan V., Ribacova G., Anisimov V. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
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Abstract: The paper studies the problem of calculating the electric field of the 110kV electric lines of CSCPL (Controlled Self Compensating Power Lines) type. The potential of electrical conductors is determined by a system of equations for voltages taking into account there phase shift at every moment of time. set of values of the voltages in the system, taking into account the phase shift of the voltage vectors in time. We dispose the possibilities that ensure to calculate the linear values of capacity and inductance of the line knowing the electric field characteristics for a given geometry. The electric line with the horizontal placement of wires is studied. The repartition of the electric field for the limited domain of a square with sides of 100x100 m, the edges of which have zero values of potential is determined. To obtain a numerical solution of Dirichlet formulated problem we will consider the domain as a set of small triangles. As the approximate solution of the formulated problem, we will consider the piecewise-defined function , which must be continuous in the domain and of linear nature on each triangle . To calculate the electric fields when changing the phase shifting angle for voltages of conductors displaced close to each other in the 0-1800 frequency band and of different values of discretization time on the period of fundamental wave of voltage, the method of finite volumes has been used. The results of numerical calculation of the character of repartition of the potential in the field of the line for different values of time and of a phase shift of the vectors of applied voltages to the conductors of close phases for the 110 kV line of CSCPL type have been showed. |
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Keywords: electric line, conductors close, finite volume method, the repartition of electric field, line parameters.
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Methods of Assessing the Efficiency of Cogeneration of Electricity and Heat
Authors: Postolaty V.M. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
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Abstract: A method that allows calculating the primary energy savings of fuel cogeneration of electricity and heat as compared to separate methods produce the same amount of these types of energy. An analytic expression relating the energy consumption of fuel for production of electricity and heat, taking into account the efficiency with the technologies of production of electricity and heat separately, and the total efficiency when these types of energy are in cogeneration. The results are illustrated by the example. Basing on these results it is recommended to amend the Law on thermal energy and cogeneration of electricity and heat concerning the methodologies for calculating performance of these types of energy cogeneration. |
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Keywords: cogeneration of electricity and heat, total efficiency, cogeneration efficiency assessment methodology.
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PWM Regulation of Grid-Tied PV System on the Base of Photovoltaic-Fed Diode-Clamped Inverters
Authors: Oleschuk V.I., and Ermuratskii V.V. Institute of Power Engineering of the Academy of Sciences of Moldova Kishinev, Republic of Moldova
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Abstract: Investigation of grid-tied photovoltaic system on the base of two diode-clamped inverters, controlled by specific algorithms of pulse-width modulation (PWM), has been done. This system includes two strings of photovoltaic panels feeding two diode-clamped inverters. The outputs of inverters are connected with the corresponding windings on the primary side of three-phase transformer, connected with a grid. In order to reduce phase voltage distortion and to increase efficiency of operation of the system, special scheme of control and modulation of inverters has been used, providing minimization of common-mode voltages and voltage waveforms symmetries under different operating conditions. Detailed simulation of processes in this photovoltaic-fed power conversion system has been executed. The results of simulations verify good performance of photovoltaic system regulated in accordance with specific strategy of control and modulation. |
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Keywords: diode-clamped inverter, photovoltaic panels and strings, schemes of control and modulation, voltage harmonic composition.
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Specific Issues of Equivalent Longitudinal Resistances Calculation for Three Windings Transformers
Authors: Golovanov N., Porumb R., Toader C., Bulac C., Triştiu I., Seritsan G. University Politehnica of Bucharest Bucharest, Romania
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Abstract: Accomplishing the aspirations of electrical power engineering consists, nowadays, in accurately determining the operating modes. Knowing the parameters of network elements is imperative for accurate solving the power flow regimes. This paper addresses unitarily the calculation of longitudinal resistance of three windings transformers and autotransformers, considering its rated parameters, and discussing the validity of relations demonstrated in detail. |
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Keywords: transformer, three windings, accurately determining, parameters.
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The principle of elaboration of the relay protection against short circuits between the closely placed phases of high voltage electrical line
Authors: Kiorsak M.1, Turcuman L.2, Turturica N.2 1Technical University of Moldova, Chisinau 2 Institute of Power Engineering of the ASM, Chisinau
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Abstract: The article is devoted to the elaboration of the principle of relay protection against short circuits between the closely placed phases of higher voltage electrical line with self-compensation, based on the six phase’s symmetrical components. It is shown that the unsymmetrical short circuits between the closely placed phases are characterized by appearance of zero and tertiary sequences of symmetrical components. This fact can be used to choose them for relay protection. The electrical basic circuits and formulas for calculation of the passive parameters of zero and tertiary filters of currents (voltages) are done. It is presented the structural-functional basic circuit scheme for relay protection against short circuits between the closely placed phases of higher voltage electrical line with self-compensation. |
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Keywords: high voltage electric line with self-compensation, unsymmetrical short circuits, zero and tertiary sequences of symmetrical components, filters, structural-functional basic circuit scheme, relay protection.
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HEAT POWER ENGINEERING
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District Heating System Using Heat Pump Installations and CHP
Authors: Sit M.L., Burciu V.I. Institute of Power Engineering of the Academy of Sciences of Moldova, Republic of Moldova, Chisinau
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Abstract: The article describes the district heating system, in which part of the heat of return water thermal power is used to supply heat to the district heating puThe article describes the district heating system, in which part of the heat of return water thermal power is used to supply heat to the district heating pumps, evaporators heating and hot water. Heat pumps use carbon dioxide as refrigerant. During the transitional period of the year, and the summer heat pump for preparing hot-water supply system uses the heat of the surrounding air. The heat of the ambient air is used in the intermediate heat exchanger between the first and second stages of the heat pump to cool the gas after the first stage of the compressor of the heat pump. |
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Keywords: district heating, carbon dioxide heat pump.
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Direct Evaporatrive Coolers of Gases and Liquids with Lowered Limit of Cooling
Authors: Doroshenko A.V., Kirillov V.H., Ludnitsky K.V., Goncharenco V.A. Odessa National Academy of Food Technologies Odessa, Ukraine
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Abstract: We have developed main technical solutions solution of indirect evaporative water and air coolers with reduced cooling limit. Packed part of heat-mass transfer devices is made of the film type based monoblock compositions of polymer materials. A mathematical model describing the processes of joint heat and mass transfer in evaporative coolers is executed. A comparative analysis of the possibilities of coolers designed based on experimental data on the efficiency of processes of heat and mass transfer. |
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Keywords: indirect evaporative cooling, heat and mass transfer equipment, film flow.
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Research of the Temperature and Humidity Processes in the Air Conditioning Apparatus Varying Air Ion Concentration
Authors: Marchenko V. G. Odessa National Academy of Food Technologies Odessa, Ukraine
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Abstract: To create comfortable conveniences for people in the room, we have to process the indoor air in the AC apparatus. Depending on given air parameters in the room, the air processing comprises the next steps: heating, cooling, wetting, drying. Except the compliance of the temperature and humidity parameters of air, we must control its ionic composition. Thereby, the experimental analysis of the air preparing in the AC apparatus is given in this article. Thank to that analysis, we can estimate the ionic and deionic impact on the air space in the specific processes of the air preparing. According to the results of experiments, we have identified, that the air temperature varying does not have significant effect on the ionic concentration. The ionic increasing after electric heater is not associated with air temperature. It is the consequence of the electron extrication from the surface of the heating element. Reducing ion moving the high air humidity decreases the concentration of the lightweight ions. The increasing of the ions in the spray-type air washers is explained by ballo-electric effect of spraying water drops, but not the air humidity rising. |
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Keywords: air conditioning apparatus; air temperature; air humidity ionization; ion moving; ballo-electric effect.
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Influence of Water Salinity on Air Purification from Hydrogen Sulfide
Authors: Leybovych L.I., Patsurkovskiy P.A. Admiral Makarov National University of Shipbuilding Mykolaiv, Ukraine
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Abstract: Mathematical modeling of «sliding» water drop motion in the air flow was performed in software package FlowVision. The result of mathematical modeling of water motion in a droplet with diameter 100 microns at the «sliding» velocity of 15 m/s is shown. It is established that hydrogen sulfide oxidation occurs at the surface of phases contact. The schematic diagram of the experimental setup for studying air purification from hydrogen sulfide is shown. The results of the experimental research of hydrogen sulfide oxidation by tap and distilled water are presented. The dependence determining the share of hydrogen sulfide oxidized at the surface of phases contact from the dimensionless initial concentration of hydrogen sulfide in the air has been obtained. |
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Keywords: hydrogen sulfide, oxidation, absorption, surface of phases contact.
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RENEWABLE ENERGY SOURCES
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Some Aspects of Micro-HPP Utilization in the Republic of Moldova
Authors: Ambros T., Ursatii N. Technical University of Moldova Chisinau, Republic of Moldova
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Abstract: The hydrografic network in the Republic of Moldova and some historical aspects of micro-Hydro Power Plants (mHPP) on the country territory have been described. There are presented some models of micro hydro damless samples developed by the Technical University of Moldova. |
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Keywords: micro-hydro power plant, dam, river, water, mill, generator, multiplier, energy.
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ENERGY EFFICIENCY
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Installation for Treatment of Agricultural Products Using High-Voltage Discharges
Authors: Popescu V.S. State Agrarian University of Moldova Chisinau, Republic Moldova
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Abstract: The paper presents the results of the study on the determination and optimization of construction and technology parameters of an electro hydraulic installation developed for research in view of its use in primary processing of agricultural products. Unlike other processing technologies, the proposed technology using electro hydraulic effect requires the application of an installation, which is simple in terms of construction, has low cost, is reliable, easy to use and can be widely applied in various branches of agriculture including primary processing of agricultural products and for sterilizing liquids. The problem of using electro hydraulic effect consists in the correct dimensioning of the installation parameters to obtain high voltage pulses, in comparison with the dimensions of the chamber with electrodes, wherein the liquid processing is carried out. For dimensioning and development of the proposed installation, the necessary parameters were determined by calculation and were confirmed by conducting operational tests. The performed calculation and tests on the operation of the installation under laboratory conditions gave the possibility of dimensioning and optimization of the construction and technological parameters of electro-hydraulic installation, i.e. voltage level, the distance between the electrodes, the volume of the treated liquid, the treatment pulse number and the energy pulsed discharge. The values of the design parameters have allowed to develop and commission the installation, which will allow further tests on use of the electro-hydraulic effect in the processing the agricultural products in the Republic of Moldova. |
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Keywords: electrohidraulic effect, electrohidraulic installation, optimal parameters, high-voltage discharges.
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Energetics of Eco-Industry of Food Concentrates Production
Authors: Burdo O, Terzsiev S, Levtrynska Ju. Odessa National Academy of Food Technologies Odessa, Ukraine
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Abstract: The determination of eco-industry in food production is formulated. The problems of processes of dehydration, heat balance and prospects of technologies directed energy action are considered. We offer the ways of solving an energy problems in product drying. The hypostases are formulated and the possibilities of laminar and turbulent diffusion to heat transfer mechanisms are analyzed. Increasing of drying speed with barodiffusional flows involvement is demonstrated. The extraction kinetic model is given in differential form. The prospects of usage directed action principles in target compounds extraction processes are analyzed. The analysis of drying technologies energy efficiency on base new similarity (similarity of energy action) is carried out. We demonstrated that impulse electromagnetic field can trigger in basically new effect, which one named mechanodiffusion. |
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Keywords: eco-industry, barodiffusion, energy, food technologies, modeling.
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Jubilee
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Vitalie BURCIU - 66 years!
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