Bulletin of NTU KhPI Series Problems of Electrical Machines and Apparatus Perfection The Theory and Practice
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Published By National Technical University Kharkiv Polytechnic Institute

2079-3944

Author(s):  
Liudmyla Zhorniak ◽  
Alexej Afanasiev ◽  
Vitaliy Schus ◽  
Olexij Morozov ◽  
Julia Rudenko

In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of operational reliability. In the article, the authors propose a method for estimating the parameters of theoretical distributions for calculating the indicators of the operational reliability of a solid insulating structure of high-voltage devices, which is a supporting insulating cover for high voltage instrument transformers filled with gas as an insulating liquid. This technique makes it possible to estimate the parameters of a new distribution law, which is chosen on the condition that it does not contradict the existing distribution law with its known parameters. The developed technique makes it possible to obtain the values of the indicators of the operational reliability of high-voltage equipment by determining the parameters of theoretical distributions, if the developer is the data of experimental studies or statistical information as a result of monitoring the operation of insulating structures, taking into account the actual operating conditions of such high-voltage devices.  This makes it possible to take into account the influence of external factors and performance characteristics inherent in instrument transformers, both current and voltage. In the proposed methodology, as an example, a supporting insulating casing is considered, which is during operation in the most unfavorable conditions, such as external pollution, humidification, overvoltage, etc. The theoretical conclusions are confirmed by the results of calculations using the example of the design of a current transformer of the ТОГ-362 series. A more accurate determination of the effectiveness of the proposed method for predicting the parameters of theoretical distribution laws can be achieved by performing an additional series of calculations and experimental tests of specific insulating structures. Thus, it was concluded that it is possible to use the results obtained to assess the operational reliability of both gas-filled instrument transformers and similar high-voltage equipment.


Author(s):  
Viktoriia Lytvynenko ◽  
Alexander Sereda ◽  
Iryna Varshamova ◽  
Olena Korol

Circuit breakers for overcurrent protection of semiconductor converters limit the duration and amplitude of the overcurrent at such a level that its thermal effect does not exceed the maximum allowable thermal protection index of the protected semiconductor device. The limitation of the thermal action of the short-circuit current is achieved by reducing the operation time of the circuit breaker. The design of the circuit breaker is changed in such a way that instead of the basic electromagnetic release is used an induction-dynamic release, which consists of an inductor with a ferromagnetic core and a rotary armature in the form of a copper disk. The electrodynamic force producing by the induction-dynamic release for quick operation is determined by the coefficient of mutual inductance of the inductor coil and the armature. Using of a ferromagnetic core entailed an increase in the coefficient of mutual inductance of the coil and armature, therefore, an increase in the electrodynamic force producing by the release, and a decrease in own tripping time of the circuit breaker. On a prototype, an experimental study of the proper operation time of the release was carried out at various values of the electrical parameters of the capacitor bank of the inductor power supply, the winding parameters of the inductor coil and the disk dimensions. The research results have proved both a decrease in the tripping time of the circuit breaker while conserving the energy of the capacitor bank of the inductor, and a decrease in the required energy of the capacitor bank to power the inductor while maintaining the minimum tripping time of the circuit breaker. Reducing the energy of the capacitor bank of the inductor made it possible to reduce the capacity and voltage of the capacitor bank of the supply of the release, and, consequently, its dimensions.


Author(s):  
Richard Mokhnach

The article describes the technology of manufacturing conductors for power supply systems for cranes, railway vehicles, powerful critical electric motors and power systems. The results of studies for copper-steel samples are shown; in these systems there is a decrease in material losses due to an increase in the strength and durability of products. The proposed technology can be used to use steel-copper wires in power supply loss compensation systems.


Author(s):  
Petr Andrienko ◽  
Vladimir Vasilevskij ◽  
Ivan Vittsivskyi

Fused Deposition Modeling is an additive manufacturing technology where a temperature-controlled head extrudes a thermoplastic material onto a build platform in a predetermined path. Standard, advanced thermoplastics and composites are used for printing. Among the areas of application for FDM printing, the main ones are rapid prototyping, as well as small-scale and batch production. The purpose of the work is the implementation of FDM 3D printing technology in the educational process of students in specialty 141 "Electroenergy, electrotechnics and electromechanics". The features of the technology of additive manufacturing of electrical apparatuses parts by the method of FDM printing have been investigated. Parts of four standard sizes were printed using ABS + and PLA plastics, namely, current transformer carcasses in the amount of 110 pieces and sensor bodies in the amount of 100 pieces. For printing, an FDM 3D printer was used built on the XZ Head Y Bed kinematic scheme with an open working chamber. The analysis of defects in finished products was carried out, which showed that the main defects are deviations of the actual dimensions and geometric shape of the finished products. Ways to prevent the occurrence of these defects are considered, namely, correcting the size of the model at the stage of preparing the model for printing, minimizing the filling density of the model, using brims in models, setting the optimal temperature of the working platform and simultaneously printing several products. The results of the study o features of the technology of additive manufacturing of electrical apparatuses parts by the method of FDM printing made it possible to develop a set of laboratory works for students of the specialty 141 "Electroenergy, electrotechnics and electromechanics".


Author(s):  
Ivan Kostjukov

The article provides an overview of the most common methods for monitoring the technical state of electrical insulation, based on the applying of absorption phenomena arising in dielectric materials under the influence of DC voltage. The main provisions of the control method based on determining the voltage at the electrodes of the investigated capacitive control object, which is recovering after a short-term discharge of its capacity, are described. The main aspects of the application of the polarization index and the absorption coefficient for determining the technical state of insulation by using the coefficients characterizing the change in time of the current through the dielectric when a constant test voltage is applied to it are analyzed. The advantages of using absorption methods for monitoring the technical state of electrical insulation, first of all, are the ability to carry out testing without the necessity of applying of relatively high test voltages, which greatly simplifies all the necessary technical operations. Such control methods show a significant dependence of the informative parameters used in them on the technical state of insulation on the degree of development of slow polarization processes in the material under study and, therefore, are successfully used to determine the degree of moisture in tested electrical insulation.


Author(s):  
Yevgen Honcharov ◽  
Nataliya Kriukova ◽  
Vladislav Markov ◽  
Igor Polyakov

The article deals with the actual problems of using the energy released by the human body. The question arises how much energy can the human body generate? Is it possible to use this energy for domestic and industrial needs? In the 18th and 19th centuries, the first scientific works on this topic appeared. It turned out that the charge carriers in the proteins of a living organism are protons and electrons, which, together with the electron-hole conduction system, create a single conductivity inherent only in a living organism. The electrical activity of the brain is assessed by voltage pulses with an amplitude of 500 μV of various frequencies from 0.5 to 55 Hz. It is impossible to receive pulses with such a frequency and such an amplitude from only ionic-type charge carriers. Electrochemical current sources are inertial; therefore, this fact can be direct evidence of the presence of electronic movement of charge carriers in the brain and the nervous system as a whole. It is quite realistic to use the thermal energy of the human body. Currently, the central building of the Stockholm railway station has been turned into a kind of experimental testing ground. Every day about 250 thousand people pass through the station building, who emit up to 25 MW of thermal energy. Most of it in the form of heated air is collected in ventilation and through heat exchangers energy is transferred to heat water in the heating system of another building. According to rough estimates, the efficiency of such a system can save up to 25% of the energy spent on heating the building. Inside a person, electric currents of various frequencies are generated in 7 biological power plants: in the heart, in the brain and in the five sense organs. All the electricity that is generated inside the human body is absorbed by its own tissues. Not a single electron produced inside a living organism leaves the human body, and does not pass into the environment, but is absorbed by the skin. This is the reason for the closure of the human electrical system. The body itself absorbs all the electricity that it previously produced. The energy generated by the human body is divided into mechanical, thermal, and electrical. The thermal energy of the human body can be used most effectively. Mechanical energy can also be used, but with much less efficiency. The electrical energy of the human body at this stage in the development of science and technology is practically impossible to use. Its use is likely to become real in the very distant future


Author(s):  
Mykhailo Panteliat ◽  
Artem Kuzmin

The purpose of the work is to improve mathematical models and algorithms of computer modeling of multiphysics processes in electromagnets and actuators of vacuum switching devices by taking into account the contact interaction of structural elements when changing their stress-strain state. In the design of modern vacuum circuit breakers and contactors, there is a significant use of electromagnetic actuators based on high-coercive hard magnetic rare earth composite materials NdFeB and SmCo. The most promising for use as drives of circuit breakers and contactors are polarized electromagnets based on the use of these high-coercive permanent magnets. However, the existing serial designs of electromagnets and actuators need to be significantly improved in order to increase reliability and service life, reduce weight and cost, further reduce energy consumption, improve the manufacturability of the mass production process. Computer simulation is proposed to be performed by the Finite Element Method in 2D formulation using commercial software products and/or software created directly for these investigations. One of the priority areas for improving mathematical models and algorithms for computer modeling of processes in the mechanical circuit of vacuum switching devices of medium and high voltage is to take into account the contact interaction of the structural elements of the devices under consideration. The next step, thanks to the use of an advanced mathematical model, is to perform a set of computational research and based on the obtained numerical results to develop recommendations aimed at creating designs of electromagnets and actuators that would meet world standards and be competitive in the world market.


Author(s):  
Vasyl Kalinchyk ◽  
Vitaliy Pobigaylo ◽  
Vitaliy Kalinchyk ◽  
Viktor Skosyrev

The article investigates the methods of control of reactive power modes. It is shown that ensuring the efficiency of electricity transmission and distribution is inseparable from setting and solving problems related to reducing electricity losses in networks. Moreover, one of the most effective ways to reduce electricity losses, as well as improve its quality at the terminals of electrical receivers is to compensate for reactive power, which is carried out using various compensating devices. It is shown that the control of the reactive power mode is carried out in accordance with the Methodology for calculating the fee for the flow of reactive energy between the power transmission organization and its consumers. It is shown that the indicator of economically advantageous value of the level of reactive energy consumption can be cos φз, the value of which is predetermined. The procedure for controlling the reactive power mode contains two main stages: the stage of determining the magnitude of the possible reduction of the current cos φ above the set and the stage of determining and implementing control effects aimed at eliminating possible deviations. Preferably, it is preferable to focus on those methods that are based on the study of forecast estimates, which constitute the source information for management decisions. It is expedient to use adaptive methods of exponential smoothing as a basis for operative forecasting of electric loading. Reactive power mode is controlled by compensating units. It is shown that the control of voltage modes in the power supply system significantly affects the modes of reactive power consumption. In this regard, it is advisable to comprehensively solve the problem of reactive power control both by controlling the compensating units and the impact on the voltage regimes of the power supply system. In the calculation model, the reactive load of the distribution network is given by its static characteristics, which can be the basis for regulating the reactive load. To implement regulation in the power supply centers of electrical networks, technical means are provided on the basis of changing the transformation coefficient or generating reactive power by counter-voltage regulation.


Author(s):  
En Dar Kim ◽  
Ian Korostelev

An alternative method for field MOV surge arresters diagnosing was observed, the controlled characteristic was the surge voltage of a gap arrester. The condenser that was connected in series with gap arrester was applied as voltage measurement sensor. Electrical aging of active elements (MOV), surge arrester insulation degradation and other types of electric faults causes to voltage increase at capacitor. The voltage value can be measured directly or the energy stored in capacitor can be transformed to electromagnetic signal and, then, registered remotely by specific radio transceiver. The capacitor connected in series with the surge arrester can also be used for leakage current limitation during all the life period of surge arrester. Shunted with a spark gap and presented as the low-current gap arrester with pre-sated discharge voltage glass (porcelain) pin-cap insulator can be the simplest, but reliable sensor.  Taking into consideration modern technologies the surge arrester statement continuous monitoring system can be designed. It also allows locating the place of damaged arrester that is particularly true for remote maintenance of equipped with surge protection devices electrical


Author(s):  
Vyacheslav Kortunov ◽  
Andrii Masliennikov ◽  
Andrii Yehorov ◽  
Oleksii Duniev

This article deals with a commercially available direct drive brushless DC motor that was investigated in the generator mode at an increased speed above the rated one. During the conducted experiments the increase of the generator rotational speed was carried out due to a three-phase asynchronous motor with 5.5 kW rated power and 2920 rpm rated speed, which was further increased by a two-stage belt gearbox with a reduction ratio from 0.16 to 1.6. However, with an increase in the rotational speed, the magnetic losses also increase, which in turn increase the required value of the input mechanical power and lead to thermal overload of the brushless DC machine. An increase the generator rotational speed leads to an increase of the EMF value and, at the same value, of the stator current, leads to an increase the generated power. Throughout the experiment, the voltage was rectified using a diode bridge and bulk capacitor, after that it was connected to a load resistance. The presented calculations of the magnetic power losses for different electrical steel grades clearly demonstrate the nonlinear dependence between the magnetic field frequency and its magnitude. Experimental studies were carried out at different speeds of rotation of a brushless DC machine in a very wide range from 140 rpm to 5228 rpm, moreover, the values of the output power were obtained depending on the rotational speed. It is concluded, that in the generator mode of the brushless DC machine, it is necessary to take into account the feature of the operation at wind power plants, autonomous power supply such as hybrid power plants. In the first case, it is worth limiting the rotational speed from the driven mechanism, and in the second case, this mode of operation may be necessary for partial boosting of output power for short-term use.


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