PNRPU Bulletin. Electrotechnics, Informational Technologies, Control Systems

Laying of power cables with XLPE insulation for 10 kV is carried out in the ground or cable channels, during laying in connection of two cable lengths. The connection is made by means of a coupling. The design of the coupling is similar to the cable design, but radially large in size for the following reasons: bolted connection of the conductors and large insulation thicknesses. When the rated current flows through the core, heat is released according to the Joule-Lenz law. The conductivity of the bolted joint is lower than the conductivity of the core, and also the coupling has a greater thermal resistance than the cable. In this article, taking into account the assumptions made and the boundary conditions, a three-dimensional mathematical model of the processes of heat transfer and electromagnetism in the cable line in conditions of laying the cable with a coupling, in the ground. The numerical realization of the mathematical model was carried out Using the finite element method in one of the ANSYS software packages in the Free environment. Plus 1×400 for a constant voltage of 10 kV. As a result of the numerical solution, there were limited fields in the coupler connection of the power cable and the environment. As a result of analyzing the results of measurements of temperature fields, acceptable permissible current loads were available.

An analytical approach to optimal pulse-width modulation is considered. In this case, the pulse width modulation means the process of approximation of the pulses (modulated) of the required voltage, the smooth (modulating) voltage, which is necessary for the formation of the load current. Current modulation error refers to the difference between the current generated by the modulated voltage function and the current generated by the modulating voltage function. The modulation quality index is interpreted as a numerical integral characteristic of a quadratic modulation (dispersion) error at a certain time interval.Two-phase modulation is a two-half-bridge modulation. For two-phase pulse-width modulation the expression of current dispersion to the load is obtained. A synthesized formula for half-bridge switching functions. It is shown that the two-phase pulse-width modulation algorithm has three free variables, which can be used to find the minimum current dispersion in the load, which is a low-frequency filter. The concept of zero potential function as a free variable, which is optimized, is introduced. We found its expression, which corresponds to the minimum current dispersion in two-phase modulation. Formulas for determining the parameters characterizing the position of pulses of half-bridge potentials at the pulse-width modulation interval are obtained. It is shown that the optimal location of the pulses on the pulse-width modulation period can significantly reduce the current dispersion at a relative modulation frequency of less than 40. When the relative modulation frequency exceeds 40 becomes the optimal modulation with the Central symmetrical position of the pulse interval modulation. The described approach to the two-phase optimal pulse width modulation can be generalized to multi-phase pulse width modulation.

The theoretical and experimental investigation of the traction effect occurring in a cylindrical linear valve motor (CLEM) between a secondary element and an inductor is considered in the article. The force acting to reciprocate the secondary element is the operating force of the cylindrical linear valve motor. The secondary element creates a force force along the axis of the motor, and the traction effect consists in the transverse attraction of the secondary element to the inductor. The forces of mechanical friction of the secondary element about the inductor arise because of the presence of a traction effect between them. As a result of the traction effect, the secondary element begins to touch the surface of the inductor, which leads to a sharp increase in the magnitude of the mechanical friction force between them. As a consequence, there is a sharp weakening of the force effort, which is a worker for the CLEM. Two different designs of the inductor of a cylindrical linear valve motor are considered in the article, their comparison is compared with the magnitude of the specific force. The forces of traction, friction, and force between the secondary element and the inductor are determined for these two different structures. The traction force is due to the displacement of the secondary element of the cylindrical linear valve motor relative to the axis of the inductor, as a result of which the magnetic gap between the inductor and the secondary element becomes uneven in magnitude. In experimental studies, it was found that the tensile force, and hence the mechanical friction, significantly weakens the working force of the CLEM. On the basis of experimental results, we came to the conclusion that it is necessary to change the design of the inducer of CLEM to reduce the traction and mechanical friction forces. The change in the design of the inductor is the use of a non-magnetic intermediate centralizer, which is inserted between two sliding bearings that are located at the ends of each module of the CLEM. In addition, the design of the magnetic flux tube of the high-voltage tube was changed, in which instead of one slot for a three-phase system of windings, three symmetrical grooves were made, each under its phase of a three-phase winding. As a result, the magnetic system of the CLEM became axisymmetric. All these measures taken to change the design of the CLEM have made it possible to sharply reduce the effect of traction, and hence the magnitude of mechanical friction, resulting in a significant increase in the specific force.

The problems associated with the loading of electric networks with reactive power and low-quality power supply to industrial consumers are considered. To solve these problems, a device based on reactor-thyristor keys on the high side of the transformer substation is proposed, which together with a capacitor Bank increases the capacity of electric networks and equalizes the voltage at consumers. To expand the functionality of reactor-thyristor switches, a control method is proposed that provides two-band continuous voltage regulation for consumers with an improved form of load voltage and current, as well as shock-free switching on of a transformer substation under load and its disconnection without the appearance of an electric arc on the mechanical contacts of electrical devices. For the study of the proposed device, complete with a transformer substation, a number of experiments on a mathematical model in the MatLab environment were performed. Analysis of the results of these experiments in stationary and dynamic modes of operation, showed the feasibility of the application of the developed technical solutions for the industrial power supply system. Oscillograms of physical processes on the model show that when the voltage in the network and the load current changes, the device provides a stable voltage at the required level, without creating a shift in the phase of the network current relative to the voltage. Describes the characteristics for the transformer substation in the nominal and with two sub-bands controller device. The proposed method and device for its implementation on the basis of reactor-thyristor keys and a capacitor bank allows for voltage stabilization in consumers, maintain the sinusoidal current in the power transformer and in the network.

The development of the country's electric power industry is focused on ensuring high reliability and efficient management of power grids with different configurations. The solution of these problems assumes a certain energy-information infrastructure. In addition to electrical equipment, it must include a set of software and hardware for data acquisition, processing and analyzing during monitoring, diagnostic and subsequent management of the grid elements condition and their operating modes. The heterogeneity of the data obtained requires the development of certain mechanisms for their processing that will allow information and diagnostic systems automatically synthesize and adapt diagnostic models to the power supply facilities operation conditions. It is proposed to develop a methodology that allows to determine the parameters of electrical equipment diagnostic models, oriented to high result reliability using data mining algorithms, in particular, fuzzy clustering. The using of fuzzy clustering on the example of the construction of membership functions that evaluate the values of equipment parameters as input variables of diagnostic models was considered. The analysis of various fuzzy clustering algorithms is carried out and a technique for processing data on the equipment operation with the membership functions construction based on the fuzzy matrix partitioning and cluster centers is proposed. The technique allows us to approximate the membership functions by typical curves and choose the most effective variant of the diagnostic model synthesis. A practical example of using the results of clustering in the development of fuzzy models for assessing the condition of the power transformer elements is considered. We obtained a high level of compliance of simulation results with experimental data on the operation of equipment in power supply systems for oil production facilities. This indicates the possibility of using the technique to ensure the accuracy of electrical equipment diagnostics by reducing errors in the recognition of critical and insignificant defects.

The production of objects made of polymer composite materials is associated with the need to research the internal structure of manufactured products using non-destructive control methods, including usage of X-rays. The extremely high importance of radiographic research is explained by the specifics of the considered objects which production is based on additive technologies. Additive technologies mean layer-by-layer build-up of the product. Thus, such defects as delamination, resin pockets, etc. can be formed in its internal structure. Often, these defects are small, but can be dangerous during exploitation. The most promising way of automation of the process of X-ray examination of products made of polymer composite materials is to create a robotic unit that automatically performs a set of interrelated operations of X-ray source and receiver positioning. The accuracy of positioning of moving elements determines the minimum size of defects that can be detected in the internal structure of the explored objects. Therefore, the information-measuring subsystem, which is designed for spatial orientation control of the mobile components of the installation, is one of the key functional blocks of the entire system. This article describes the problematic issues of constructing of the information-measuring subsystem of the robotic complex. The mathematical support which is the base for the operation of the inclinometer modules is described. Much attention is paid to hardware testing and investigation of the influence of various power sources on the stability of inclinometer measurement data. The results of the experiments are shown in graphical and tabular form. The article can be useful for developers in the sphere of industrial automation. In addition, the given information can be used by engineers and scientists for the design of control and management systems of unmanned units, because it is necessary to correctly and accurately determine the parameters of spatial orientation for successful functioning of such objects.

In this paper, the process of heat and mass transfer in the cable channel with 18 cable lines, each of which consists of three cables with a core cross-sectional area of 150 mm2 located in the pipe, was studied. Based on the finite element method, a two-dimensional mathematical model of the thermal field of an underground cable channel is developed. The temperature distribution fields in the cable channel and the surrounding ground for different cable lines loading variants were obtained. To assess the effect of heat loss in the copper cable screen the dependences of the maximum temperature of the cable core on the current value are obtained. Options with and without heat loss in the screen are considered. In the work the possibility of replacing a layered cable design for the equivalent layer for the purpose of simplification of the accounting model is analyzed. Maximum temperature values and temperature fields in the cable line for different values of the current load at the multilayer structure and equivalent layer are obtained. In this paper, the question of choosing the location of backup lines is considered. The temperature field for the case of full load of all cables is built to determine the lines, which are in the worst temperature conditions. The expediency of choosing certain lines as backup lines is proved by calculating the maximum temperature of the cable cores. Taking into account all the findings, the maximum load conditions for each cable line, provided that the cable core temperatures do not exceed the maximum permissible values, were selected. The task was solved using the finite volume method in the engineering calculations environment Fluent.