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  Problemele energeticii regionale

E-Journal №2(31)2016



0 Electroenergetics
1 One Core Phase Shifting Transformer for Control of the Power Flow Distribution in Electric Networks
Authors: Golub I.V. Institute of Power Engineering of the Academy of Sciences of Moldova Chisinau, Republic of Moldova
  Abstract: This paper presents the variant of phase shifting transformer that is made, unlike from traditional technology, on the basis of only one magnetic core. The paper describes the methodology related to the analysis of operation modes of device and its components. Additionally it presents a mathematical model of device with determines the relationship between input and output electric quantities as well as own longitudinal and transverse parameters of an equivalent circuit of phase shifting transformer (PST). Proposed configuration of PST is interesting from an economic and operational consideration; enable continuous control of power flow distribution in electric networks as a result of regulation a phase shift angle between input and output voltages of device.
  Keywords: phase shifting transformer, vector diagram, pie charts, phase shift angle, a complex conversion factor.
2 Small Distributed Renewable Energy Generation for Low Voltage Distribution Networks
Authors: Chindris M.1, Cziker A.1, Miron Anca1, Sacerdotianu D.2 1Technical University of Cluj-Napoca, Cluj-Napoca, Romania 2ICMET, Craiova, Romania
  Abstract: Driven by the existing energy policies, the use of renewable energy has increased considerably all over the world in order to respond to the increasing energy consumption and to reduce the environmental impact of the electricity generation. Although most policy makers and companies are focusing on large applications, the use of cheap small generation units, based on local renewable resources, has become increasingly attractive for the general public, small farms and remote communities. The paper presents several results of a research project aiming to identify the power quality issues and the impact of RES based distributed generation (DG) or other non-linear loads on low voltage (LV) distribution networks in Romania; the final goal is to develop a Universal Power Quality Conditioner (UPQC) able to diminish the existing disturbances. Basically, the work analyses the existing DG technologies and identifies possible solutions for their integration in Romania; taking into account the existent state of the art, the attention was paid on small systems, using wind and solar energy, and on possibility to integrate them into suburban and rural LV distribution networks. The presence of DG units at distribution voltage level means the transition from traditional passive to active distribution networks. In general, the relatively low penetration levels of DG does not produce problems; however, the nowadays massive increase of local power generation have led to new integration challenges in order to ensure the reliability and quality of the power supply. Power quality issues are identified and their assessment is the key element in the design of measures aiming to diminish all existing disturbances.
  Keywords: renewable energy sources, distributed generation, PV systems, small wind turbine, active distribution networks.
3 Innovating Technological Process for Expanding the Service Life of Underground Power Cables
Authors: Tabacaru V.1, Brinton R.2 1 Filiala Electrica Distribuţie Muntenia Nord S A. - SDEE Galati, Galati, Romania 2 Novinium, Auburn, USA
  Abstract: As a public power distribution operator on low voltage (023/0.4 kV), medium voltage (6 and 20 kV), and high voltage (110 kV) in the territory of Galati County, SDEE Galati serves approximately 240,000 consumers (captive and eligible, domestic and non-domestic For this purpose, in the field of medium voltage underground distribution lines, SDEE Galati manages and operates a volume of approx. 500 km UDL/6kV circuit and approximately 630 km UDL/20 kV circuit. Many of these cables which are still in operation, were manufactured with materials and on the technological level of the ’60s,’70s and ‘80s decades and have reached the end of their service life. Evidence does and incident statistics from these networks in which, every year, one of the "tips" is the medium voltage cables damaged "technical wear" normal operating conditions. The current paper will present the main features of an innovating technological process called SPR (Sustained Pressure Rejuvenation), designed for on-site refurbishing of underground power cable insulation medium and high voltage. The process offers a viable alternative that has proven, over the 25 years of application initially on the American content and now on the worldwide, substantially more cost effective than replacing cables. The paper does not propose detailed presentation of the technological process, but to inform the family of energetics NPS about the existence and the benefits of applying this new technological process to the old cable medium and high voltage.
  Keywords: cables, insulation, rejuvenation.
4 Analysis of Partial Discharge Activity for Evaluation of the State of High Power Electric Generators Stator Windings
Authors: Dumitrescu Sorin INCDE ICEMENERG, Bucharest
  Abstract: The paper shows the importance of trending of partial discharge activity in assessing the insulation condition. It is presented the principle of the measurement method and the quantities that characterize partial discharges and also the criteria utilized for the assessement of the insulation condition of the hydrogenerators. Results of the measurements made on several hydrogenerators are presented, like the variation with time of the two main quantities that characterize the partial discharges, maximum magnitude, Qm and the normalized quantity, NQN over a period of about 10 years. Further, a classification of the insulation condition by 3 main and 2 intermediary categories and the definition of these categories are given. The criteria used for the assessment of the insulation condition are presented in the form of a table: quantitative criteria by the ± NQN and ± Qm values and qualitative criteria for the analysis of the 2D and 3D diagrams. At the end of each set of measurements, an analyze of the insulation condition annual evaluation is made, also a verdict is put, and of course, the recommendations made relating to the maintenance and the decisions that have been taken. The paper ends with several considerations on the method of on-line partial discharges and especially, on the conditions for valid trending activity in time.
  Keywords: partial discharges, measurement method, hydrogenerators, stator insulation, condition, evaluation, trending, maintenance.
5 Three-element Reactor-Capaсitor Device for Flexible Link Between Non-Synchronous Power Systems
Authors: Bosneaga V.A., Suslov V.M. Institute of Power Engineering of the Academy of Sciences of Moldova, Chisinau, Republic of Moldova
  Abstract: Short review of known variants of flexible controlled interconnections between asynсron power systems was fulfilled. The basic characteristics of three-element reactor-capacitor device, providing controlled power transmission and reactive power internal balance for connected power systems with different levels of voltages, were investigated. Mathematical model was elaborated for calculation of parameters of reactor-capacitor device elements, necessary for realization of circular rotation of output voltage phase angle at fixed load admittance. These results allow estimating the required range of the admittances changing, necessary to ensure control of transmitted power by means of semiconductor switching devices.
  Keywords: controlled, flexible connection of AC power systems, combined reactor-capacitor device.
6 Propagation of disturbances as voltage fluctuations in transmission networks
Authors: Albert Hermina1, Golovanov Nicolae2, Elefterescu Luminiţa 1ISPE, 2University POLITEHNICA of Bucharest Bucharest, Romania
  Abstract: Significant changes occurred in the power system in Romania in recent years by reducing the power used in the system, the number of classic power sources in operation as well as by implementing renewable energy sources, have determined short circuit power reduction (node rigidity) in the points where disturbing users are connected, that in the absence of adequate measures, result in disturbances above acceptable levels. The paper analyzes two power systems areas in which are connected users that cause voltage fluctuation. Disturbances as voltage fluctuations resulting in these nodes may exceed the acceptable values and can spread in the transmission network affecting power quality over large system areas. The analysis conducted reveals the influence of short circuit power in nodes where these users are connected and highlights the fact that in some cases (e.g. lines out of operation for maintenance, shutdown of classic units in the area) the disturbances in the transmission network sent to the users at lower voltages may have values above those allowed. Technical Code of existing power transmission network makes no reference to voltage fluctuations, as a rule, in the electricity transmission network was considered that this phenomenon should not exist.
  Keywords: voltage fluctuations, transmission networks, electric energy, quality.
8 Energy Address Delivery Technologies and Thermal Transformations in Food Production
Authors: Burdo O.G. 1, Sit M.L. 2, Zikov A.V. 1 , Reznychenco D.N. 1, Juravleov A. A.2 1 Odessa National academy of food technologies, Odessa, Ukraine 2 Institute of Power Engineering of the ASM, Chisinau, Republic of Moldova
  Abstract: In this article, energetic and technical paradoxes in food nanotechnologies and traditional ap-proaches to evaluation of energy recourses using are considered. Hypotheses of improvement of food production energy technologies are formulated. Classification of principles of address de-livery of energy to food raw materials elements is given. We had substantiated the perspective objectives for heat-pumps installations and biphasic heat-transfer systems. The energy efficien-cy of new technologies is compared on base of the number of energy impact. Principles of mass transfer modeling in extraction, dehydration and pasteurization combined processes are consid-ered by food production example. The objectives of mathematical modeling of combined hy-drodynamic and heat and mass transfer processes in modern energy technologies are set. The fuel energy conversion diagrams for drying, innovative installations on the base of thermal si-phons, heat pumps and electromagnetic energy generators are represented. In this article, we il-lustrate how electromagnetic field, biphasic heat-transfer systems and heat pumps can be effec-tive tools for energy efficiency technologies.
  Keywords: energy, food technologies, modeling, heat pumps, heat pipes, electromagnetic energy supply.
9 Engineering method of calculation temperature fields and thermal stresses in the initial stage of radiation convection heating (cooling) body with variable heat transfer coefficient, and the temperature of environment
Authors: Gorbunov A.D., Uklеina S.V. Dneprodzerzhinsk State Technical University Dneprodzerjinsk, Ukraine
  Abstract: Existing solutions of radiant and convective heating (cooling) body problems at the initial stage at unsteady heat transfer coefficients and temperatures are rather cumbersome. The purpose of this work is getting simpler dependencies. Decisions are based on the analysis of relations between the cause (heat flow) and the effect (surface temperature) in the initial period of heating. Two simple and effective engineering methods of calculation of unsteady temperature fields, and axial thermal stresses at the initial stage of heating (cooling) of body of canonical form for both convection and radiation heat transfer at variable ambient temperature and environmental factors have been developed. Some of the solutions are generic in nature, which allows significantly reducing the number of variables and thus using the graphical method of problem solving. The formulas for calculating the bulk and central temperature in the initial stage are provided; other researchers of nonlinear heat conduction problems did not usually do this. It has been found that the axial thermal stresses are determined entirely by the heat flow on the surface. The adequacy of the developed techniques is based on five cases of calculation of heating (cooling) plates under various conditions of its thermal loading. It is shown that the error in determining the surface temperature does not exceed 6%, and that the developed method can be used up to Fourier numbers .
  Keywords: сonvection, radiant heating (cooling), the initial stage, unsteady temperature fields, variables heat transfer coefficients, thermal stress, and engineering method of calculation.
10 Improving the Energy Efficiency of Mechanical and Thermomechanical Food Technology Systems
Authors: Bezbah I.V., Chepin N.I., Voscresenscaia E.V. Academia naţională de tehnologii alimentare din Odesa Odesa, Ucraina
  Abstract: The drawbacks of the equipment for mechanical and thermomechanical treatment of food products are considered. The ways of solving energy problems in technologies of heat treatment of food liquids, drying of dispersed products, and separation of stone fruit crops are proposed. Designs of dryers and apparatus for heat treatment on the basis of rotating thermosiphons are shown. The results of experimental studies of the drying processes, the heat treatment of foods in the machines with rotating thermosyphons have been presented. The models for the calculation of heat and mass transfer processes in heat treatment and drying of food products in these devices had been offered. Descriptions of the machine of rotary type for separation of stone fruit crops have been done. The economic efficiency of the proposed re-direction of primary processing of stone fruit crops has been proved. The modified Newton number is used for generalizing experimental results. The Euler number is used to take into account the energy characteristics of the machine. The criteria equations have been suggested for design and optimization of this class of machines. The proposed devices are able to provide the effective heat transfer in processing of dispersed viscous foodstuffs and to reduce the energy loss up to 30%.
  Keywords: thermomechanical processing, energy, food technology, modeling.
12 Applied Data Analysis in Energy Monitoring System
Authors: Kychkin А.V., Mikriukov G.P. Perm National Research Polytechnic University Perm, Russia
  Abstract: Software and hardware system organization is presented as an example for building energy monitoring of multi-sectional lighting and climate control / conditioning needs. System key feature is applied office energy data analysis that allows to provide each type of hardware localized work mode recognition. It is based on general energy consumption profile with following energy consumption and workload evaluation. Applied data analysis includes primary data processing block, smoothing filter, time stamp identification block, clusterization and classification blocks, state change detection block, statistical data calculation block. Time slot consumed energy value and slot time stamp are taken as work mode classification main parameters. Energy data applied analysis with HIL and OpenJEVis visualization system usage experimental research results for chosen time period has been provided. Energy consumption, workload calculation and eight different states identification has been executed for two lighting sections and one climate control / conditioning emulating system by integral energy consumption profile. Research has been supported by university internal grant №2016/PI-2 «Methodology development of monitoring and heat flow utilization as low potential company energy sources».
  Keywords: energy data, energy monitoring, energy data visualization, applied data analysis, pattern recognition, OpenJEVis, Janitza.
DOI: 10.5281/zenodo.1208218
13 Improved Method of Detection Falsification Results the Digital Image in Conditions of Attacks
Authors: Kobozeva A.A., Grigorenko S.N. Odessa National Polytechnic University Odessa, Ukraine
  Abstract: The modern level of information technologies development has led to unheard ease embodiments hitherto unauthorized modifications of digital content. At the moment, very important question is the effective expert examination of authenticity of digital images, video, audio, development of the methods for identification and localization of violations of their integrity using these contents for purposes other than entertainment. Present paper deals with the improvement of the detection method of the cloning results in digital images - one of the most frequently used in the software tools falsification realized in all modern graphics editors. The method is intended for clone detection areas and pre-image in terms of additional disturbing influences in the image after the cloning operation for "masking" of the results, which complicates the search process. The improvement is aimed at reducing the number of "false alarms", when the area of the clone / pre-image detected in the original image or the localization of the identified areas do not correspond to the real clone and pre-image. The proposed improvement, based on analysis of different sizes per-pixel image blocks with the least difference from each other, has made it possible efficient functioning of the method, regardless of the specificity of the analyzed digital image.
  Keywords: digital image, cloning, violating the integrity, digital image matrix, interpolation spline, disturbing influences.
DOI: https://10.5281/zenodo.1208220
14 Identification of Application Areas of the Steganalytic Approach Based on the Analysis of Spatial Domain of Digital Contents
Authors: Akhmamet’eva A.V. Odessa National Polytechnic University Odessa, Ukraine
  Abstract: In this paper the identification of application areas of previously developed steganalytic approach based on accounting of quantity of consecutive triads in the matrix of unique colors of digital images, from the point of view of formats of digital contents is carried out. The influence of the size of the digital contents, which are used as containers for the embedding of additional information, on the detection efficiency during steganalysis is analyzed. As a result of fulfilled computational experiments, it has beet stated that the developed approach is effective for digital content in losses formats, and it has been turned out a restriction on size of the containers. Results of computational experiments are demonstrated.
  Keywords: steganalysis, the spatial domain of the container, a digital image, losses format, lossless storage format.
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