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A CASE STUDY COMPUTATIONAL ANALYSIS OF LITHIUM BROMIDE SOLUTION FOR HOUSEHOLD ABSORPTION HEAT TRANSFORMER
Steam compression installations operating from electric energy are widely used in the world for air conditioning. This type of installation has a number of disadvantages, and therefore a new air conditioning installation has been proposed. Ab-sorption heat transformer is an air conditioning and hot water installation based on the principle of an absorption heat pump. The installation can also be used for heating. The installation is able to use renewable energy sources or utilize the heat of exhaust gases as heat sources: for example, from a heating boiler with a temperature of up to 115 °C. The practical significance of the installation lies in resource conservation and environmental friendliness. The use of this installation will ultimately reduce the consumption of primary fuel and reduce the negative impact on the environ-ment. The paper considers the possibility of using a lithium bromide solution in an absorption heat transformer for resi-dential premises. For this purpose, a number of calculations were carried out, according to the calculation method of ab-sorption refrigerating lithium bromide machines. As a result of the calculations, it was established that the use of lithium bromide solution is satisfactory for use in a household heat absorption transformer. However, in order to achieve greater efficiency, the installation scheme requires refinement.
PROCESSES OF POLLUTION AND CLEANING OF TURBINE OIL IN LUBRICATION SYSTEMS OF STEAM TURBINES
The dependence of the parameters (cleanliness, contamination and purification) of the working fluid of the bearing lubrica-tion system and steam turbine control is obtained. Filters are intended to purify by removing solid contaminants that are harmful to the oil and the machine. If the filter is doing a good job, it is removing contaminants as fast as they are entering (ingression). This is known as mass balance. The number of particles coming into the oil system (particle ingression) equals the number being caught by the filter (particle removal); this achieves a stabilized and controlled oil cleanliness lev-el. The effect of air dispersed in oil on the operation of frame filters in steam turbine lubrication systems was analyzed. It has been established that when filtering aerated oil, soft particles (gas bubbles) increase the screening ratio of solid con-taminants by more than 4 times. Calculations show that air dispersed in oil increases the purity of the filtrate in the system by 21 times.
ELECTRIC DRIVE SYSTEM OF PIPE ROLLING MILL PJSC “CHELYABINSK PIPE PLANT”
The relevance of the presented work is to increase the speed in the operation of the pipe cold rolling mill for a possible in-crease in technical and economic indicators. In the pilot plant, it was decided to take the KhPT-450 machine (PJSC Chel-yabinsk Pipe Rolling Plant), the speed of which was increased to 30 % by switching on energy-efficient equipment. The analysis of cyclic automation showed that the operating time of the electric drive is about 30 %, which gives a positive technical and economic indicator. In view of this, it was decided to take a decision from the mechanical power circuit of the bevel gear, which in turn turned into a mechanical part of the system. However, reducing the gear ratio of the gearbox leads to a dynamic load on the motor shaft. The analysis of the work of the technological process with the help of the technique of synthesis of the power part of the electric drive is carried out. The method includes several stages of analysis: determination of the trajectory of motion parameters, electrical equipment, structure selection, as well as corrective connection parameters. This method allows you to give a complete reverse opera-tion of the electric drive. As a result, the speed, position, and torque control loop data is carefully correc¬ted. In the Agree-ment, a feasibility study was carried out from the introduction of the presented methodology. The indicators show that the positive effect is not only manifested in the speed of work by 80 %, but the economic effect is also growing in a positive way.
DESIGN OF IMPROVED CONTROL ALGORITHMS FOR LADLE FURNACES WITH ANALYSIS OF ELECTRIC ARC CURRENT HARMONIC COMPOSITION
The aim of this research is the design of improved control algorithms for ladle furnaces, considering arc length adaptation to different argon blow conditions and slag layer depth. The paper considers the issues of optimizing asymmetric arc burn-ing regimes, which ensure the maximum reduction in radiation and an increase in thermal efficiency in phases located near the liquid metal mirror during bottom blowing and emergency lance operation. The experimental results of liquid bath sur-face behavior in dependence from blowing intensity and slag layer depth are presented. On the basis of experimental re-sults, new algorithms of electric modes control in ladle furnaces are proposed. These algorithms allow dynamic adaptation of electric arc lengths to different argon blowing modes and slag layer depth to be provided. Applying of this algorithm al-lows the requisite conditions for improving of different quality indicators in ladle furnace to be ensured, since the correct adaptation of electric mode to varying conditions of melting has a direct con-nection with thermal efficiency of electric arcs and efficiency of equipment in general.
COMPARATIVE EVALUATION OF THE METHODS OF POWERING THE PMSM IN A THYRATRON MOTOR MODE
The article provides a comparative assessment of various ways of powering a synchronous motor with permanent magnets (PMSM) in the mode of a thyratron motor (TM). Numerically, on analytical and computer models, mechanical ω = f(M), the dependence of speed on electromagnetic torque, and energy ηэ = f(M), the dependence of electromagnetic efficiency are calculated from the moment, the characteristics of the motor with sinusoidal power supply and discrete switching with dif-ferent values of the relative inductance of the winding. Moment pulsations are investigated. The three most common meth-ods of discrete degree commutation are considered – 120, 180 and 150. It is shown that discrete 120 degree commutation provides the highest value of ηэ in comparison with other methods, and the mechanical characteristics are approximately the same in appearance with different power supply methods. The study of moment pulsations has shown that discrete switching without additional measures cannot compete in this indicator with the case of sinusoidal power supply, which theoretically has zero moment pulsations. However, the use of 150 degree commutation makes it possible to significantly reduce them, bringing them closer to 2…3 %. Curves are given that allow an approximate estimate of the expected moment pulsations for all discrete switching methods. Practical recommendations on the choice of the method of powering the PMSM are given.
ASSESSING THE INFLUENCE OF ONE-WAY MAGNETIC ATTRACTION FORCES ON THE RELIABILITY OF THE BEARING UNIT OF A SWITCHED RELUCTANCE ELECTRIC MACHINE
The object of the study is a switched reluctance electric machine with an uneven air gap. The main objective of the research is to assess the influence of the forces of one-way magnetic attraction on the reliability of the bearing unit for different variants of the rotor location. This article takes into account the mutual influence of the forces of one-way magnetic attraction and the imbalance forces. The finite element method was used to calculate the magnetic field. The study examined a switched reluctance machine in which the rotation axis is aligned with the symmetry axis of the stator or offset together with the symmetry axis of the rotor. The values obtained were those of a resulting force of one-way magnetic at-traction which substantially exceed permissible values. The study proposes an algorithm for calculating the characteristics of a valve-inductor electric machine, taking into account the tolerances for the manufacture of its structural elements. The algorithm allows for the requirements for the bearings used to be adjusted. This then ensures the required level of reliabil-ity of the switched reluctance electric machine, and predicts the level of vibration and noise.
FAULT LOCATION IN ELECTRIC 35–10–6 kV NETWORKS ACCORDING TO EMPIRICAL CRITERIA IN THE COORDINATES OF THREE SYMMETRIC COMPONENTS
The paper investigates the method of detecting fault location in 35–10–6 kV electrical distribution networks based on empirical criteria in the coordinates of three symmetrical components, specific for each type of emer-gency mode. Voltages and currents of the direct, reverse and zero sequence are used in the formulas of the criteria. The formulas themselves were developed according to the following principle: if voltages or currents increase when the fault point moves along the length of the line, they are used as numerators, and if vice versa, the voltages or currents values are used as denominators. For each criterion, a graph of the interpolating function was obtained which is stored in the computer's memory. When a fault occurs, the value of the criterion is calculated and, according to the graph, the place of the emergency mode is found. The calculated mathematical error of the developed method is revealed with a small measurement error of ±0.2 %. It is shown that all errors are less than 1 %, except for single-phase earth fault modes, when the error reaches 2.6 %. As calculations show, the error of the fault location is directly proportional to the resulting measurement error and the accuracy of setting the initial data. So, with a resulting accuracy of ±2.5 %, the maximum error of the fault location is close to 3%, and with an accuracy of ±5 %, it is close to 6 %. Existing fault de-tection devices operate with an error of 3–20 %. Moreover, they are unable to detect damage with ground faults and breaks. The effectiveness of the considered method is confirmed by technical and economic calculations. So, based on one 35, 10 and 6 kV feeder, the economic effect is 200, 150 and 110 thousand rubles per year, respectively, with a payback period of about a year. When applying the method for 1000 feeders, the effect will be about 200, 150 and 110 million ru-bles per annum. Thus, the criteria obtained for fault location are effective from both technical and economic points of view.
CALCULATION OF ZIP LOAD MODEL COEFFICIENTS IN THE NEARBY PARTS OF THE ELECTRICAL NETWORK USING MEASUREMENT DATA
The article discusses the methodology for recalculating the coefficients of ZIP load model in nodes of electric networks 35–220 kV, according to the experimental data obtained for some another network nodes. The need to recalculate the static load characteristics for nearby parts of the network arises due to problems between networks owners and the insufficient number of certified measuring equipment during the active experiment, as well as the impossibility of connecting the measuring equipment in some places of the electrical network. For recalculation, a model of an electrical network section is formed and standard models of network elements such as transformers, currentlimiting reactors and power lines are used. These models are divided into elementary multipoles and the calculation is performed sequentially for each of them. The given technique is general and allows recalculating the ZIP model coefficients of the load at an arbitrary point of the electrical network according to experimental data at some points of the network.
MATHEMATICAL MODELING OF A HYBRID WIND-SOLAR STATION FOR POWER SUPPLY OF OWN NEEDS
The article presents mathematical modeling of a hybrid power plant (GEU) operating on renewable energy sources. The GEU includes a wind module, a solar module, and an electric power storage system. It is supposed to use the GEU for power supply of the botanical garden's own needs, the principle of operation of the station is described. The analysis of monthly data of average insolation and average values of wind speed in the Orenburg region is carried out. The real schedule of loads of the botanical garden is used for calculations. The analysis is based on data on solar insolation and wind speed over the past 20 years. It is revealed that the greatest generation of solar electricity during the year occurs in the period from June to July, and the greatest generation of wind electricity during the year occurs in the period from January to March. The total generation makes it possible to provide the botanical garden's own needs with electricity in any month except October and November. The excess electricity generated in the summer can be used for the production of hydrogen, which is used as fuel for a hydrogen fuel cell or its storage in storage devices.
DESIGN AND SIMULATION OF A SOLAR-WIND STAND-ALONE SYSTEM WITH A SEVEN-LEVEL INVERTER
During an energy conversion process, the total harmonic distortion and losses will increase while its power stability decreases. Multilevel inverter technology can be utilized to alleviate the shortcomings of conventional inverters. These technologies have become recognized as cost-effective solutions for a wide range of industrial applica-tions. Reduced component losses and lower switching losses, as well as improved output voltage and current wave-forms are the first advantages of this design. In multilayer inverters, elimination of harmonic components in the inverter output voltage and current is crucial. This paper proposes a system that consists of three different renewable energy sources. Two of them are PV solar systems while the third is wind turbine simulated in MATLAB Simulink. Seven-level inverters based on switch reduction techniques are proposed in this paper. The proposed system design is verified in the absence of PV systems to produce five voltage levels as a contingency in PV systems.
A STUDY OF THE PARAMETERS OF THE 6 kV ELECTRICAL NETWORK AT TARRORSKY QUARRY
In order to ensure continuity in the supply of electrical energy to electrical receivers, as well as for the purposes of the safe and reliable maintenance of electrical installations under operating voltage, the insulation parame-ters according to which organizational and technical measures are being developed needs to be known. The use of such measures will allow ssocial and economic benefits to be achieved.This article discusses the method developed to establish insulation parameters in quarry distribution networks (QDN). Using the methodology developed, a study was conducted in the “Tarror” quarry. During the study the dynamics of changes in the insulation resistance of the phases of the network relative to the ground was evaluated. Based on the results obtained, it was concluded that such measure-ments should be undertaken at least one year in advance. This will enable reasonable qualitative and quantitative conclu-sions to be drawn about the influence of environmental parameters on the insulation resistance of the phases of QDN rela-tive to the ground.
Technological safety in electrical energy engineering
METHODS AND MODELS FOR DEFINING OPTIMAL RELIABILITY PARAMETERS IN DISTRICT-DISTRIBUTED HEATING SYSTEMS
District-distributed heating systems are considered to be the result of the development of existing district heating systems. In such the various energy technologies are integrated in order to achieve maximum efficiency of the heating for consumers. The distributed sector in these systems is associated, first of all, with the implementation of prosumers. The objective of the study is to define parameters for the reliability of components in the system which provide the required level of reliability of heating to consumers at the minimum cost. This is while ensuring the level of reliability while taking into account the reserve functions of prosumers. A methodology aimed at solving the objective thus stated was developed using various methods and models. These included: certain laws of reliability theory, nodal approach to the reliability analysis, models of the Markov random process, laws of thermophysical processes, heat load curve, etc. The proposed methods and models are presented within a comprehensive methodological schematic which includes the main stages of analysis and optimization (synthesis) of reliability. The methodological and computational tools thus developed were used to conduct a computational experiment for a test diagram of a heating system. The results obtained were analyzed, and their graphical interpretations presented. The conclusions and directions for further research were formulated.
FEATURES OF SYNTHESIS OF SYNCHRONOUS RELUCTANCE AND INDUCTOR ELECTRIC MACHINES
The problem of finding the best dimensions for the elements of magnetic systems of synchronous reluctance and inductor electric machines in an extended range of changes in load torque and power is considered. An algorithm for solving the problem is also proposed, involving the division of the elements of the magnetic system into two groups. The first group affects the magnitude of the torque pulsations, while the second does not affect this indicator. Such partitioning accelerates the process of convergence of the result. A method of sequential non-linear programming is proposed for resolving the problem. It has good convergence with minimal search time. Synthesis of finite element models of a synchronous reluc-tance machine with salient pole and anisotropic types of rotors, switched reluctance machine (SRD), machine with field switching (FSDC), Vernier reluctance and double field Vernier reluctance machines was performed. It was shown that the proportion of winding copper relative to steel in the active part of the machines increases relative to conventional machines when operating in the nominal mode. On the contrary, this feature was manifested to a lesser extent when working in the zone of overloads in terms of torque. Electromagnetic loads increase with increasing power, equivalent to operating a machine of lower power in overload mode. It was shown that the sensi-tivity to the size of the air gap in Vernier reluctance machines is the highest in the class under study. Thus, with increasing power, the specific torque will increase significantly. On the contrary, the lowest sensitivity to the air gap value in ma-chines with one-sided gearing and distributed winding on the stator allows these machines to be made with a larger gap without compromising the specific torque.
ANALYSIS OF EXCITATION SYSTEMS OF SYNCHRONOUS GENERATORS OF FACTORY POWER PLANTS
One of the priorities in the development of metallurgical enterprises is to increase own generation of electricity. At the largest enterprises in the sector – PJSC MMK (Magnitogorsk), Severstal PJSC (Cherepovets), PJSC “NLMK” (Lipetsk) Electricity generation is 60–70% of total consumption. This contributes to two factors: firstly, the presence of secondary fuel gases – coke and domain; and secondly, unreasonably high electricity tariffs. Thus there is an urgent need to ensure sustainable trouble-free operation of factory generators and basic systems. Automatic excitation control systems (ARV) are the most important factor when determining the state of the generator in various modes. The main requirements for ARV systems determine the specific working conditions. We will highlight the most significant and significant of these. 1. Low power 10–50 MW generators are connected to an external power system on 110 kV buses, where the short circuit capacity is within 3000–5000 mba. Thus the possibilities of regulating and maintaining voltage are very limited. 2. Since the electricity produced by its own power plants is 2–2.5 times cheaper than purchased power, almost all generators work with a power factor close to one. This significantly reduces their stability in the power supply system. 3. The voltage at the point of connection and loading of the Eigen needs for the generator voltage stations are unsta-ble. Therefore, in order to preserve the stability of generators in transient modes, the most preferred is the ARV system with a switching structure in which the settings and regulation laws are selected depending on Work modes. The work gives a general review of the existing laws and the proposed arousal regulation law, adapted to the condi-tions of factory generators of small and medium-sized power, working concomitantly with a high power grid.
MPPT FOR HYBRID WIND, SOLAR AND THERMOELECTRIC POWER GENERATION SYSTEMS FOR OFF-GRID APPLICATIONS
Renewable energy resources for electrical generation are normally free but are not continuously available due to their sporadic availability. Thus, hybrid connections of various kinds of energy are made to increase utilization of renew-able energy. This paper involves a design of a hybrid renewable energy system employing maximum power point tracking (MPPT) techniques. The hybrid system consists of solar PV panels, a small-scale wind turbine, and a thermoelec-tric generator (TEG) module. Four MPPT techniques are examined in this research. They are the incremental conductance (IC) algorithm, fuzzy logic controllers (FLC) using 25 and 35 rules, and an interval type 2 fuzzy logic con-troller (IT2FLC). Each MPPT technique is tested in the system to determine which has the best maximum power tracking, stable operation, and efficiency. All of the studied energy resources are connected to a DC linked bus. The voltage of this bus is supplied to a three-phase inverter. Inverter output voltage is regulated for balanced and unba¬lanced loads. The generating capacity of the designed hybrid system is 5 kW and the system is simulated using MATLAB Simulink R2017a.
METHOD OF ESTIMATING SPECIFIC POWER CONSUMPTION AND ELECTRODE WEAR AFTER CORRECTION OF ELECTRIC MODES IN ELECTRIC ARC FURNACES
The paper describes an improved method for estimating the technical effect after correction of electric modes in electric arc furnaces and ladle furnaces. The main indicators of efficiency for these types of equipment are specif-ic power consumption and electrode wear. The study shows that after correction of electric modes in electric arc furnaces and ladle furnaces through parameterization of electric mode control system (or implementation of new control system), estimation of these parameters may be inaccurate. This is caused by the inapplicability of direct comparison of specific power consumption and electrode wear over separate time periods, due to the impact of different technological fac-tors. In contrast with existing methodology, the improved method takes into account the impact of technological factors with unequal values over separate time samples. The new method is based on statistical and correlation analysis of electri-cal and technological characteristics for pre-warranty and post-warranty periods. The most unfavourable period for achiev-ing the technical effect is determined on the basis of average values analysis. Further estimation of the technical effect is provided in relation to the most unfavourable conditions. The proposed method may be applied for a more precise assess-ment of the efficiency of electric arc furnaces and ladle furnaces after adaptation of parameters in electric mode control sys-tem or after the replacement of a control system.
STUDY AND MATHEMATICAL MODELING OF A LITHIUM-ION BATTERY
This study considers existing methods of mathematical modeling of lithium-ion batteries based on the Shepherd formula, as well as using formulas from the general course of physics. In order to measure experimental data in automatic mode, a special measuring facility was developed, the main element of the setup is a programmable platform based on the ATmega328p microprocessor. It controls the process, measures the voltage on the battery and transmits data to the computer every 5 seconds via the UART interface of the microprocessor for further analysis.
FORECASTING AND MANAGING THE MICROGRID COMMUNITY USING ARTIFICIAL INTELLIGENCE
A characteristic feature of the modern electric power industry in recent decades is the sharp increase in electricity consumption. This can be explained by technological, social, economic, and other reasons. Therefore, the forecasting of electricity consumption is important for many processes, including the planned operation of genera¬ting equipment and managing and optimizing the operating modes of energy systems. It is also a significant aspect in the opera-tion of industrial enterprises, since breaches can result in fines. One of the urgent tasks in the electricity market today is the forecasting of electricity consumption for a certain period. The article presents a description of a microgrid model with a built-in block for predicting power consumption, as well as intelligent load control for several objects at the same time, including those with distributed generation. Decisions are made the previous day, in order to forme stra¬tegies or the generation profile and control of power receivers. This timing is dictated by the information available to the intelli-gent system. This information includes forecast of demand and electricity prices of the centralized energy system for every hour of the next day. The process of switching at peak time to additional sources of electricity, distribution over microgrids is also described. The forecast was implemented using the Holt-Winters model from the statsmodels library (Python 3). The model uses the ideas of exponential smoothing, but is more complex and can be applied to series containing trend and seasonality. The trained model predicts with 95.21% accuracy.
APPLICATION OF METHODS FOR THE JUSTIFICATION OF ENERGY SAVING MEASURES IN THE POWER SUPPLY SYSTEMS OF MINING ENTERPRISES
The paper uses the methods of mathematical modeling and instrumental control to justify the introduction of energy-saving measures and technical solutions in the power supply systems of mining enterprises. An assessment of the implementation of energy saving methods in electric drive and power supply systems at mining enterprises demon-strated the possibility of achieving a multiplier economic effect with the right approach to the implementation and subse-quent operation of energy-saving technologies. The energy saving potential was shown in the industry in ge¬neral, and in mining enterprises in particular. For example, in some areas of enterprises, such measures as reactive power compensa-tion, the introduction of automated electric drive systems, the development and pilot operation of power quality control systems with continuous recording of indicators were considered. The mathematical modeling method was implemented using the MatLab software package which has proven itself in engineering calculations around the world. Instrumental control and evaluation of power quality indicators were carried out in accordance with the requirements of GOST RF 32144–2013. As a result of the potential optimization of individual power supply systems, the estimated total economic ef-fect due to energy savings was obtained. The figure approached 28 million rubles per year, which is on average 20% of the cost of electricity consumption of the considered sites of mining enterprises.
ON THE IMPERFECTION OF TERMINOLOGY IN ELECTRIC POWER FACILITIES DEVELOPMENT
The regulatory documentation in the electrical power industry contains such terms as “technical re-equipment”, “reconstruction”, “expansion”, “modernization”, “repair” and “operation”. Some of them are easily defined while the specific differences of some terms require deeper study of regulatory documents in the technical, legal, account-ing and tax areas. At the same time, the incorrect use of these terms can lead to problems both in industrial activities and in related areas, and lead to precedents in judicial practice. In order to establish the differences between the designated terms, the article provides an analysis of normative documents, analyzing the concepts used in them. It attempts to establish the meaning and scope of the terms and the semantic links between them, while analyzing cases of practical application. The study provides recommendations on the use of each of these terms and a conclusion is made about the need to improve the existing regulatory and methodological framework concerning the modernization of electric power facilities.
EXPERIMENTAL STUDY OF AERO- AND HYDRAULIC SYSTEMS IN A DIRECT-FLOW BOILER ON A LABORATORY STAND WITH THE INTRODUCTION OF AUTOMATIC CONTROL OF DEVICES AND DATA COLLECTION
Few laboratory stands can simulate the operation of direct-flow boilers. The processes occurring therein are complex both hydraulically and thermophysically. A study of the fluid dynamics of the coolant in a cylindrical compo-site coil shows that it is possible to influence boiler performance. The movement of air through coils is also of interest for the intensification of the heat exchange process in direct-flow steam boilers. Modern automation devices can make allow for readings to be taken of the coolant and air with high accuracy. They cal also transfer experimental values to a personal computer for data storage and subsequent analysis. The article presents the results of the design and assembly of a laboratory stand, designed for experimental research of aero- and hydraulic systems of a direct-flow boiler using automatic device control and data collection. The results of modeling and experimental data are presented herein.
ERROR ANALYSIS OF THE INDIRECT METHOD FOR MONITORING NETWORK ISOLATION PARAMETERS RELATIVE TO THE GROUND IN MATLAB/Simulink
The insulation parameters of electrical installations must be determined to find methods to prevent electrical injuries and ensure the safety of operation and reliability of power supply to electricity consumers. By identifying areas showing a steady decrease in insulation during operation and repairing such areas in a timely manner, the reliabi­lity of power supply and operational safety can be significantly improved. Complete information about the insulation of electrical installations can be obtained by applying appropriate insulation monitoring methods. The article offers a brief description of existing methods for determining the parameters of network isolation relative to the ground and analyzes the errors of the indirect method based on connecting to one of the phases of additional capacity. A computer model of the influence of various factors on the accuracy of measurements of the insulation parameters of the network phases relative to the ground was analyzed. The analysis showed that with phase voltage asymmetry and changes in the magnitude and type of load, the measurement error of the proposed method does not exceed 8%.
OPTIMISATION OF NEW TYPES OF ELECTROMECHANICAL CONVERTERS FOR MECHANISMS WITH FAN-TYPE LOADS
Тhe article considers the main requirements for pumping stations, in particular, for methods of regula­ting the water supply at the first lift pump unit. A description of the pumping unit and equipment is provided. The artic­le provides a comparison of the types of the main drive units of pumping stations. It also provides a rationale for the choice of electric drive system between classical asynchronous and synchronous electric drives, as well as a system with a field regulated reluctance machine (FRRM) with a comparison of energy indicators. A description and substantiation of the control system work are also given. The articles provide the technical characteristics of the motor parameters and the daily flow rate of the station fluid. The optimal method for regulating the power supply system was chosen based on research. A mathematical model of the device which implements the chosen control method is presented. The results of mathematical modeling are presented in the graphs. A graph of the transient process is given in the case of changing speeds depending on the required fluid supply. Conclusions about the efficiency of the system are drawn and further action plans are outlined.
DIAGNOSIS OF THE ELECTRIC DRIVE OF THE DISCHARGE ROLLER CONVEYOR OF A WIDE-STRIP HOT MILL
The purpose of the study is to develop an automated system for technical diagnostics of the state and regulation of the electric drive of the rollers of the collector roller table at a wide hot rolling mill based on change in the load currents of the rollers electric motors. The system allows the quality of finished rolled products and the productivity of the mill to be enhanced due to the timely detection of faulty equipment and its rapid replacement based on the results of diagnostics. The following methods of diagnostics of the electric drive of the diverting roller table and its possible malfunctions which can negatively affect the quality of the finished rolled products were analyzed: experimental identification of the relation of the forms of change in the load currents of the electric motors of the rollers with specific types of malfunctions; determination of diagnostic signs of malfunctions in the values of change in the load currents of the electric motors of the rollers; creation of a mathematical model for calculating the forces of strip transportation; development of methods and algorithms for technical diagnostics of the electric drive of the collector roller table based on characteristics of change in the load currents of the electric motors of the rollers; development of a generalized algorithm for the operation of the automated technical diagnostics system; experimental evaluation of the effectiveness of the proposed methods and algorithms for diagnostics on the operating mill. Analytical methods of solving algebraic and differential equations and systems were used in the study. As a result of the research, the technical effectiveness of the methods and algorithms developed to diagnose the eccentricity of the roller barrel of the diverting roller table, malfunctioning of the brush-collector device of the roller electric motor, the destruction of the couplings in the roller electric drive line, malfunctioning of the bearing units in the roller electric drive line or the roller sides, the correct alignment of the roller relative to the technological plane of the diverting roller was experimentally confirmed. The diagnostic methods and algorithms developed can be used to create diagnostic systems for electric drives of diverting roller table at operating mills during their reconstruction, as well as at newly built mills. The system thus developed was installed at the industrial plant's 2000 hot rolling mill.
DETERMINATION OF ASYNCHRONOUS MODE AND METHOD TO CONTROL THE EXCITATION OF A SYNCHRONOUS ELECTRIC MOTOR
The paper presents the results of research aimed at identifying the asynchronous mode of excited synchronous electric motors and their safety and stability. It is proposed to identify the asynchronous mode using a power polynomial from the ratio of the degrees of active and reactive power, determined from measured instantaneous values of currents and stator voltages of a synchronous electric motor. It is proposed to control the excitation system of a synchronous motor by cyclically switching the excitation winding to an additional resistance or an exciter based on a criterion representing the derivative of the power polynomial from the ratio of the active and reactive powers of the synchronous motor. The proposed methods for detecting the asynchronous mode of excited synchronous motors and controlling the excitation system to ensure successful resynchronization of a synchronous motor without unloading the driven unit can be used in microprocessor-based protection devices for synchronous electric motors. The effectiveness of the proposed methods is confirmed through mathematical modeling.
METHOD FOR DIAGNOSING DAMAGE TO SQUIRREL-CAGE ROTOR OF INDUCTION MOTOR IN RUN-DOWN MODE
The proposed work is intended to deepen the theoretical foundations of constructing systems for diagnosing damage to the squirrel-cage rotor of an induction motor in run-down mode. It presents a method for diagnosing damage to the rods of a squirrel-cage rotor of an induction motor by means of EMF induced in the stator winding by damped currents in the squirrel-cage winding of the rotor. According to this method, the device is designed on the basis of a personal computer in which a sound card is used as an ADC, and the data is processed in specially created software. Two block diagrams of the device for diagnostics of blood pressure are presented, Information about the damage to the rotor is obtained from the EMF of the stator, and the start of the run-down is determined by the difference in its amplitudes or by the closure of the switch block-contacts. In the latter case, when the block-contacts of the load switch are opened, a signal is generated to measure the EMF of the stator winding and this EMF is recorded. This diagnostic system makes it quite easy to diagnose blood pressure with voltage up to 1000 V. However, the need to connect high-voltage AMs to the block-contacts for diagnostics, for example, in switchgear cells, significantly complicates the diagnostic process and so for technological reasons it cannot be used on all AMs. This can be largely avoided, if the beginning of the IM run-out mode is determined by the amplitude difference. The prototype of the rotor bar breakage diagnostics system has shown that its implementation is capable of quite efficiently detecting the rotor bar breakage in the IM run-down mode. In this case, experimental data was obtained both with the use of a computer sound card and an external certified ADC/DAC module. It was found that the measurement error with a sound card is permissible. At the same time, the cost of the entire device is low and is mainly determined by the cost of the PC and software making it affordable for almost any industrial enterprise and non-profit organizations.
ENSURING UNINTERRUPTED POWER SUPPLY TO HIGH-TECH POWER ENTERPRISES
The article considers the need to ensure reliable power supply to high-tech enterprises, taking into account two location options: near the city or power lines, and in a territory remote from it. The problem of using only one power source for such enterprises is connected to current instability in frequency and voltage changes, as well as planned or unscheduled power outages in the power transmission line network. A variant of an automated power supply system is proposed as a backup source. This includes AC power from an external network and power from a combined wind-solar installation. The study proposes schemes for the joint use of wind-solar installations and external sources for enterprises located near power lines. It further proposes a scheme for the joint use of power lines with recuperators and thermoelectric generators, in those cases when enterprises are located beyond the reach of power lines. The result of this proposal is a constant, high-quality and uninterrupted power supply to high-tech power plants at any time of the year and under any weather conditions.
EXPANDING THE FUNCTIONAL CAPABILITIES OF A THYRISTOR FIELD DAMNING DEVICE FOR INTENSIFICATION OF PROCESS CONTROL
The article considers the operation of a commonly known thyristor device for dampening a synchronous generator magnetic field. Improvement in the characteristics of the device and expansion of its functionality with a known control algorithm requires an increase in the number of quenching circuits. The article proposes an algorithm for controlling damping circuits based on the principle of binary coding of the decimal value of the required equivalent resistance of the device. The current-voltage characteristics of the device have been determined for two variants of circuits of thyristor field damping devices. An increase in the average value of the voltage at the terminals of the excitation winding and an increase in the quality of synthesizing the required current-voltage characteristic were noted. The article further describes the advantages and disadvantages of the described algorithms and schemes. It has been proven that the transition to a new control algorithm for damping circuits improves the characteristics of the thyristor device for dampening the synchronous generator magnetic field without the need for changes in the power section. However, this requires measures to be taken, in order to improve the reliability of the control system.
DEVELOPMENT OF AN AUTOMATED CALCULATION SYSTEM FOR DETERMINING THE RATIONAL CROSS-SECTION AND VOLTAGE LEVEL OF 10–35 KV POWER LINES FOR IMPROVING THE ECONOMIC EFFICIENCY OF THE CALCULATED VALUES
As shown in general terms by the statistics of emergency shutdowns and limit periods of operation of electric grid elements and electrical equipment, the main objective when connecting prospective industrial and residential complexes is to ensure uninterrupted power supply. To this end, new prospective and power lines for consumers need to be reconstructed or laid. This requires the development and implementation of automated calculation system with improved methodology for selecting cross sections of conductors of 10–35 kV power lines. This also needs to take into account a number of additional economic parameters, including the criterion of minimum discounted costs. This has resulted in new values of economic current density for each subject of the Russian Federation, corresponding to new economic conditions which differ significantly from those given in PUE. The study performed an analysis of the influence of economic current density on the territorial dispersion of electric power prices, discount rate, dynamics of load growth and prices for repair and maintenance. This confirms dependence on the economic situation in the country. The software product developed as a result enables recalculation of the power line for further reconstruction and mo­dernization. In addition, as mentioned above, values were calculated for all regions of Russia, taking into account highest load time. The use of the automated calculation system will reduce the time needed for calculation when determining the type of line, cross-section and voltage for further forecasting of newly connected facilities as well as existing ones, it will also enable a correct and justified choice with a minimum of initial information.