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E-Journal №2(46) 2020

"PROBLEMS of the REGIONAL ENERGETICS"

CONTENTS

0	The Optimal Variant for Introducing Southern Transit into the Integrated Power System of Ukraine Authors: Kyryk V., Kravchenko Y. National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute” Kyiv, Ukraine
	Abstract: Abstract. The work solves the problem of assessing the operation modes of the Integrated Power System (IPS) of Ukraine taking into account the power flows increase to the states borders for integration into the ENTSO-E power system. The Transmission System Development Plan for 2021-2030 is considered, in which the construction of southern transit power lines is planned. The issue of the redistribution of power flows in the electric network with the possibility of transferring power from the eastern regions of Ukraine to the western ones is considered. The analysis of the optimal increase in the connection cross-section into ENTSO-E networks by in-troducing southern transit. The purpose of the work is to analyze and evaluate the introduction of southern transit power lines by a high voltage direct current network based on voltage source converters in the electric network of the Ukraine power system. This problem was solved with creating a model of an electric network of 750 and 330 kV of the Ukraine IPS, analyzing the simulation results and comparing the network operation modes when introducing southern transit by an alternating and direct current. The most significant results of the work are the proof of the technical feasibility of introducing southern transit on direct current with the ability to influence the capacities flow distribution. Significance of the obtained results consists in the development of the Ukraine IPS model with the direct current lines introduction, which allows to analyze the electric network operating modes while introduction of southern transit by direct current.
	Keywords: multi-terminal DC grid, voltage source converters, longitudinal-transverse regulation, operating modes, power system of Ukraine. DOI: https://doi.org/10.5281/zenodo.3898058
1	Calculation Improvement of Equivalent Power of Hydrostatic Drive for Crane Mechanisms Authors: Strizhak V., Anishchenko G., Strizhak M., Turchyn O., Masliennikov A. National Technical University «Kharkiv Polytechnic Institute» Kharkiv, Ukraine
	Abstract: The aim of this study is to determine the analytic dependences of modifying the equivalent power of electric motors of hydrostatic drivers for different operation cycles of traveling and rotary mechanisms of lifting machines taking into account the power consumption during the idle run (when the mechanism remains immobile), which was not accounted for earlier. The latter is the novelty of this work. To achieve the goal the stand experimental studies were performed for the traveling mechanism of the bridge crane with a hydrostatic adjustable drive, the schedule status review of the electric energy consumption was carried out for all the stages of the operational cycle. The analytic dependences were defined of changing the equivalent power of the driver throughout all stages of the operational cycle, namely, acceleration, motion at a stable speed, and braking. Based on these dependences, the specified analytic expression to calculate the equivalent power for the full operational cycle was obtained, which is the most important result of the study. The significance of the result consists in that the specified calculation with the use of the proposed analytic dependences will allow using a simple method to estimate heating more objectively. It will as well enable to justify the selected power of the electric motor with the hydrostatic driver of the motion mechanisms and rotary motion of lifting machines that operate in starting-up-braking modes under conditions of varying parameters of the operational cycle.
	Keywords: electric motor, power consumption, adjustable drive, hydraulic drive, bridge crane, traveling mechanism, operational cycle. DOI: https://doi.org/10.5281/zenodo.3898062
2	Information-Measuring System for Monitoring the Climate Impact on Overhead Power Lines Authors: Shilin A. N., Shilin A. A., Dement’ev S.S. Volgograd State Technical University Volgograd, Russian Federation
	Abstract: Studying the problem of diagnosing high-voltage lines is the goal of this research. The high acci-dent rate of overhead lines due to icing and current overloads makes this problem important. Current overloads during distributed power generation lead to overheating of the lines. The goal of the research is achieved due to the fact, that the article notes the relationship between icing and overloads. The necessity of joint solution of these problems and the development of the concept of a multifunctional measuring system is proved. For this, an analysis of the main pa-rameters that determine the mode of operation of overhead lines is carried out. Technical solu-tions for the measurement of these quantities are considered. The detection of ice formation by comparing the values of dew points and desublimation is described. The calculation of the limit-ing current load taking into account weather conditions is given. The amount of sagging wires is selected as a universal characteristic of the state of the line. A significant result of the study is the optical method of icing control. This method consists in measuring the coordinates of the line wires through a weatherproof CCTV-camera. To do this, optical tags and a temperature sen-sor are placed on the wires. The optimal architecture of the measuring system for assessing the climatic impact is given. The significance of the results is that a multifunctional and high-precision system without expensive load sensors is proposed. The conclusion about the im-portance of the results for building a smart grid is made.
	Keywords: smart grid, reliability of power supply, telemetry system, icing diagnostics, OHL temperature monitoring, weather conditions monitoring. DOI: https://doi.org/10.5281/zenodo.3898086
3	Modelling of Electrical Discharge Processes for Optimization of Corona-Protection System of High Voltage Rotating Machines Insulation Authors: Andreev A.M., Andreev I.A., Belko V.O., Reznik A.S., Smirnov A.N., Stepanov A.A. Peter the Great St.Petersburg Polytechnic University St.Petersburg, Russia
	Abstract: The aim of this work is to study the influence of technological defects in stator windings electri-cal insulation system on the inception of partial discharges in the stator slot of air-cooled electric rotating machines. By means of Comsol Multiphysics finite-element modeling software the elec-trophysical processes in high-voltage stator insulation with corona-protection coatings are nu-merically studied for both Resin-Rich (RR) and vacuum pressure impregnation (VPI) technolo-gies. The most important results are the conclusions made about the possibility of slot partial discharges in the insulation system of stator windings, taking into account the possible types and sizes of technological defects of the anti-corona coating in the slot area. The verification of the results of mathematical modeling by experimental study of slot partial discharges on test samples with artificial defects of anti-corona coatings made possible to establish the most dangerous types and geometric sizes of defects, which lead to the inception of slot partial discharges, which determined the practical significance of the results. Quantitative dependencies between the geo-metric dimensions of coating defects and the characteristics of slot partial discharges (inception voltage, maximum apparent charge, and average current) are experimentally established. The obtained data have practical importance for the development of the optimal technology for manufacturing the system of electrical insulation of the stator winding of high-voltage air-cooled electric machines.
	Keywords: electric machine, stator slot, anti-corona system, slot partial discharge. DOI: https://doi.org/10.5281/zenodo.3898227
4	Ways to Improve the Efficiency of Pipelines Heat Insulation Authors: Struchaiev N., Postol Y., Stopin Y., Zhuravel D., Hulevskyi V. Dmytro Motornyi Tavria State Agrotechnological University Melitopol, Ukraine
	Abstract: A significant part of thermal energy is lost precisely during its transportation. By increasing the efficiency of thermal insulation of pipelines, it is possible to reduce significantly heat loss around the world. The purpose of the paper is to develop and validate methods for increasing the efficiency of thermal insulation of pipelines by determining its optimal location. This purpose has been achieved by applying of a modified method for studying the process of heat loss, taking into account the radiation component, to calculate the heat loss and surface temperature of the thermal insulation with different spatial arrangements. For comparison, we analysed three options for the heat loss of pipe with a different spatial arrangement of thermal insulation coated with an aluminium reflective film facing outward, facing inward and in both directions. Comparison of these variants showed that it had been advisable to insulate the pipelines by installing an insulation layer coated with an aluminium reflective film facing in both directions. The main result of paper has been the proposed method for calculating of heat losses, which could be used in the design of thermal insulation of pipelines and the obtained data confirming the correspondence of theoretical calculations to actual values of the surface temperature of thermal insulation taking into account its various spatial arrangements. The importance of the results of the work lies in the possibility of using this technique to assess the effectiveness of thermal insulation of pipelines and determine the best solutions for its spatial location.
	Keywords: energy saving, thermal insulation, pipelines, thermal conductivity, energy losses, compact heat-insulating elements. DOI: https://doi.org/10.5281/zenodo.3898231
5	Metal Consumption of Heat Engines and Heat Capacity of their Working Fluids Authors: Kiselev V.G., Kalyutik A.A., Kukolev M.I. Peter the Great St. Petersburg Polytechnic University Saint Petersburg, Russian Federation
	Abstract: Ensuring efficient energy supply in general and heat supply in particular together with creation of air conditioning systems is a very urgent task of modern energy industry, particularly acute in the absence of large centralized energy sources. The cost of such systems is largely related to the cost of heat engines operating both in the direct and reverse cycle, in its turn determined by their construction and installation costs that are directly related to their metal consumption. Our goal was to reduce metal consumption of heat engines. It had been achieved with the use of thermo-dynamic potentials and thermodynamic cycles in conjunction with a model idea of the ideal gas, Carnot and Phillips heat engines, etc. The most significant result was mathematical formulas that for a given efficiency linked the heat capacity of the ideal gas with the geometric dimensions of heat engines under consideration, the working cylinder volume of the Carnot heat engine and the amount (volume) of metallic mesh participating in heat exchange with the working body of the Philips heat engine. Significance of these results lies in establishing a steady trend of reducing metal consumption of Philips and Carnot heat engines with a reduction in heat capacity of the ideal gas used as their working body. As Carnot and Philips cycles are model cycles used for analyzing other heat engines, including those utilizing real gas systems, this clearly shows the possibility of reducing metal consumption of real heat engines while reducing heat capacity of their working fluids.
	Keywords: heat engine, thermodynamic potentials, Gibbs free energy, cycle, ideal gas, metal consumption, heat pump, refrigerator, compressor. DOI: https://doi.org/10.5281/zenodo.3898237
6	Experimental Investigation of Two-Phase Closed Thermosyphons for Boiler Economizers Authors: Epifanov A. A., Dymo B. V., Dolganov Y. A., Anastasenko S. N. Admiral Makarov National University of Shipbuilding Мykolaiv, Ukraine
	Abstract: Improving the reliability and reducing the overall dimensions of economizers of low-power boilers are urgent tasks. A promising direction for solving this problem is the use of two-phase closed gravitational thermosyphons. The lack of experimental data on the thermal efficiency of thermosyphons in the operating conditions of economizers of low-power boilers determines the relevance of this work. The aim of the work is an experimental study of the thermal efficiency of thermosyphons, as well as heat transfer processes during phase transitions of a working fluid (demineralized water), under operating conditions of economizers.The thermosyphon was made of a steel pipe with an internal diameter of 0.028 m: the boiling zone length of 1.5 m and the condensation – of 0.5 m. It has been established that the thermal power of the thermosyphon was varied in the range of 350...990 W with a change in air inlet temperature in the range of 190...310 °C and cooling water – of 60...100 °C. It was established that the temperature of the thermosyphon wall exceeds the dew point of the combustion products for high sulfur fuel oil by at least 5 °C. The most significant results of the work are the obtained data on the heat transfer ability of thermosyphons, as well as recommendations on the choice of dependencies for calculating the heat transfer coefficients during boiling and condensation of the working fluid. The significance of the obtained results lies in the fact that the method of thermal calculation of thermosyphon economizers was improved due to the recommended dependencies for calculating the internal thermal resistances of thermosyphons.
	Keywords: boiler, economizer; two-phase closed thermosyphon; experimental investigation; thermal efficiency; boiling; condensation; thermal calculation. DOI: https://doi.org/10.5281/zenodo.3898239
7	Solar Absorption Air Conditioning Systems Based on Low Temperature Evaporative Air Coolers Authors: Doroshenko A.V., Antonova A.R.,Kovalenko S.A. Educational and Research Institute of Refrigeration, Сriotehnology and Eco-Energetics Odessa National Academy of Food Technologies, Ukraine
	Abstract: The purpose of the study is the creation of a new generation of evaporative air coolers, providing a reduction in the limit of evaporative cooling from the temperature of the wet thermometer to the dew point of the incoming air stream. The goal was achieved due to the exclusion of traditional refrigeration vapor compression equipment from air conditioning systems. The result of theoretical and experimental studies of low-temperature evaporative air coolers was the development of circuit solutions for evaporative low-temperature coolers in an autonomous form. The analysis was carried out taking into account modern solutions (patents) and publications in leading foreign scientific publications of recent years. The authors carried out an analysis of the danger of moisture "recondensation" that is characteristic specifically for the processes of low-temperature evaporative cooling of air. The authors made recommendations to prevent this phenomenon, leading to a sharp decrease in cooling efficiency. The authors carried out a series of experimental studies of hydroaerodynamics and heat and mass transfer processes in low-temperature air coolers. The values of the "delay" of the liquid in the packed layer were determined. These data make it possible to calculate the real wetting of the surface of the packed layer, which are fundamentally important when switching to multi-channel packed structures of polymer materials. The results obtained allow us to expand the field of practical use of evaporative cooling methods, for example, to achieve air comfort parameters in the air conditioning system with a developed, more effective than the traditional, circuit design.
	Keywords: : low temperature evaporative air coolers, air coolers - chillers, solar absorption systems, air draining, evaporative cooling, cooling limits. DOI: https://doi.org/10.5281/zenodo.3898274
8	System of Innovative Energy Technologies of Food Raw Material Dehydration Authors: Burdo O.G.1, Terziev S.G.2, Gavrilov A.V.3, Sirotyuk I.V.1, Shcherbich M.V.1 1 Odessa National Academy of Food Technologies, Odessa, Ukraine 2 PRJSC ENNI FOODS, Odessa, Ukraine 3 Academy of bioresources and nature management “Vladimir Vernadskiy CFU”
	Abstract: The market trends of food products of long-term storage, instant cooking and functional purpose are analyzed. The problems of energy technologies for the production of such concentrates were identified. The aim of the study is to develop energy technology systems that guarantee a high degree of raw material target components preservation during energy costs reducing. To achieve this aim the hypotheses of the implementation of innovative projects, based on the technology of address energy delivery to the elements of food raw materials were formulated. Physical, par-ametric and mathematical models of evaporators and dryers with electromagnetic energy sources were presented. The results of a study of the drying kinetics on a belt plant with combined infra-red and microwave generators were analyzed. The most significant results of the work are: mathematical models of heat and mass transfer processes under the electromagnetic energy ac-tion, a complex of kinetic dependences during plant material drying, samples of innovative equipment for dehydration of food raw materials using microwave and infrared energy sources. The significance of the obtained results lies in the fact that energy-intensive drying is excluded from traditional technologies for the concentrate production. Implementation of innovative pro-jects for the concentrate production from food raw materials in the extractors and evaporators reduces energy expenditures by 1.5–2 times from 39.5 MJ per kg of removed moisture to 11.4 MJ. High quality products are ensured, since more than 80% of the volatile aromatic and flavor-ing compounds that are lost in the spray dryer are fully preserved.
	Keywords: food concentrates, energy technologies, modeling, infrared and microwave apparatuses, heat and mass transfer. DOI: https://doi.org/10.5281/zenodo.3898317
9	Combined District Heating System CHP- Local Heat Pumps. Part II Authors: Sit M.L., Juravliov A.A. Institute of Power Engineering of Moldova, Chișinău, Republic of Moldova Suvorov D.M., Suvorova L.A. Vyatka State University, Kirov, Russian Federation
	Abstract: The paper discusses options for district heating systems, including thermal power plants and heat pumps installed in individual heating centers of multi-storey buildings. The aim of the work is to evaluate the energy efficiency of the options under consideration and the method of connecting piping to high-temperature return network water with a carbon dioxide heat pump. The goal is achieved due to the fact that one of the evaporators of the heat pump heating the new building or half of the existing building uses heat from return network water or from the first half of the building or from the whole building, and the second evaporator uses the heat of the outdoor air. Moreover, for high-temperature heating schedules, heat is taken out through a two-stage inter-mediate circuit containing two pumps, 2 heat exchangers and two expansion vessels. Significant results of the work are the developed scheme of the intermediate circuit of the carbon dioxide heat pump, which combines both the possibilities of working in a quantitative heat supply sys-tem and in the preparation of hot water for buildings during the non-heating period. The signifi-cance of the obtained results lies in the fact that the proposed technical solution allows to reduce fuel consumption for thermal power plants, consumers' expenses when paying for their con-sumed energy resources, increase the number of heat consumers connected to the thermal power plants through the use of heat pumps. The schemes of intermediate circuits of heat pumps for the quantitative law of regulating the operation mode of the heat supply system are also consid-ered.
	Keywords: district heating system, heat pump, carbon dioxide, control law, CHP, temperature. DOI: https://doi.org/10.5281/zenodo.3898322
10	Increase of the Biogas Output during Fermentation of Manure of Cattle with Winemaking Waste in Biogas Plants Authors: 1Polishchuk V.M., 1Shvorov S.A., 2Krusir G.V., 1Davidenko T.S. 1 National University of Life and Environmental Sciences of Ukraine, Kyiv, Ukraine 2 Odessa National Academy of Food Technologies, Odessa, Ukraine
	Abstract: The aim of the work is to increase biogas output and generation of electricity in biogas plants due to the joint fermentation of cattle manure with winemaking waste. To achieve this goal, the following tasks were solved: the biogas yield from cattle manure with winemaking waste was determined during periodic loading of the digester; on the basis of the obtained experimental data, a mathematical model was calibrated to estimate the biogas yield during fermentation of cattle manure with the addition of winemaking waste. As a result of the studies, it was found that when manure is fermented with part of the water replaced in the substrate 2% of the winemaking waste, the fermentation dynamics in the substrate are similar to the fermentation of pure cattle manure. Biogas obtained by fermentation of manure with the addition of 2%, 6.5% and 13% of wastewater from wine production instead of water in the first day of fermentation either did not burn at all or burned poorly. The addition of winemaking waste to a substrate based on manure in an amount of 13% allows increasing the maximum biogas yield by a third to 1,372 l/(hrkg dry organic matter). The significance of the research results lies in the fact that the use of winemaking waste as a substrate will allow a third increase in biogas output and power generation, and a reduction in the payback period of a 4,4 MW biogas plant using the green tariff to 6,5 years.
	Keywords: biogas, substrate, cattle manure, winemaking waste, dry organic matter, digester, biogas plant, methane fermentation. DOI: https://doi.org/10.5281/zenodo.3898326