Vol 90, No 11 (2019)

The load distribution between 18 cable lines located in an underground cable channel is considered. It is found that a current distribution control system in the cable channel needs to be developed to optimize the load conditions, as well as prevent possible overheating. The possibility of using a mathematical model of heat and mass transfer processes in the channel to determining the optimal current loads of cable lines is considered. A mathematical model of heat and mass transfer processes in the cable channel is constructed that makes it possible to study the temperature conditions of the channel under different configurations and line loads. Search algorithms of optimal operating currents under varying loads are developed that take into account the requirements for permissible temperatures and categories of consumers. The unsteady condition of overload of one of the lines due to an emergency is investigated. The heating curves of current-carrying conductors of the emergency cable line and those adjacent to it are plotted. The value of the current is determined to which it is necessary to reduce the load in one of the lines to maintain the system operability.

When an air-jet (turbojet) engine is operated, continuous parameter monitoring is required—specifically, of the gas temperature behind the combustion chamber (gas chamber, rotational frequencies of the free pressure turbine, rotational frequencies of a turbocharger rotor, etc.). The operation of the circuits is regulated by a selective controller, which asynchronously logically continuously controls the flow of fuel (kerosene, gas) through the metering device and analyzes the deviations of parameters of a turbojet engine. All circuits have software control and implement the principle of regulation by deviation. The software implementation of the control circuit operation of the turbojet engine is performed by the engine control unit (ECU). The calculations of optimal settings of regulators in the circuits are performed according to the technical optimum, provided that the static characteristics are constant. However, the actual static characteristics of a turbojet engine change during operation and the previously calculated settings of regulators in the circuits may not be optimal. Software control of the system enables the appropriate selection of coefficients from the ECU memory without taking into account the changes in the static characteristics of the turbojet engine at the current time. This method of calculating control system parameters is not effective, since it requires an exact mathematical description of the object and its changes at a given instant in time. Other uncertainties involve the conditions of the dispenser elements, fuel quality, etc. Currently, the aforementioned parameters are all regulated separately, which is a disadvantage. It has been proposed to replace regulators of the turbojet engine parameters with one regulator of state that would control the dispenser in order to eliminate the selector from turbojet engine control. A fuzzy state controller made on the base of adaptive fuzzifier with a fuzzy implication is considered. To adapt the fuzzifier, the objective function is used, with the help of which the coefficients of first-order polynomials are calculated.

The tools for soft computational technologies are based on the fuzzy systems, models of fuzzy neural networks, genetic algorithms, etc., which have advantages and drawbacks. In this paper, these tools are considered as applied to a 3D printer. From the point of view of control theory, a 3D printer is a complex nonlinear object, the mathematical description of which is a priori known, with one input and several outputs. During the operation of a 3D printer, it is required to provide continuous monitoring of such parameters as temperature of filament heating, rotation speed of a dc motor for feeding the filament to the extruder, and linear replacement of the carriage of a 3D printer. The operation of circuits is regulated by the controller of state, which, by analyzing the deviations of parameters, synchronously logically continuously controls the temperature of filament heating, feeding the filament to the extruder, and linear replacement of the carriage. The target function for all the circuits takes a given value of the adjustable parameters. The hybrid (fuzzy-neural) control over a 3D printer is based on the designing of a state controller using the special fuzzifier with the use of asymmetric sigmoid functions and the formation of layers to carry out fuzzy implication. The conversion of fuzzy information into determined information is carried out in a converter (decoder) that controls the printer voltage within the given range.

The normal magnetization curve of electrical steel is usually represented as an approximation curve or is set as points using a smoothing method of some sort. The equations of normal magnetization curves of electrical steel have yet to be derived due to the difficulties of physical representation of the processes occurring in ferrimagnetic materials. An attempt is made in this work to describe mathematically the magnetization of ferrimagnetic materials in the physical representation of domains, which produce a magnetic field with rotation of magnetic induction vector. Equations of normal magnetization curves of electrical steel are derived that coincide with reference data with sufficient accuracy.

In this paper, we consider intelligent diagnostic systems providing effective control of electric equipment of electric network facilities. To maintain equipment operability, a level model is proposed. The model is distinct in integrating various methods of analyzing and processing dissimilar data of equipment operation in order to reliably assess its technical condition using nondestructive control technologies to determine the real need for maintenance and repair. The model is focused on intelligent support of the electrical personnel activities and involves calculating the integral priority indicator to assess the necessary maintenance activities and choose the most appropriate control actions. A method for diagnostic control during the electric equipment operation, which can be used for electric network facilities of various configurations, is developed. The technique involves the adaptation to equipment operating conditions for the timely identification of defects and reducing the duration of planned and unplanned downtime. The results of technique testing on the example of electrical equipment of oil production facilities are presented. The proposed solutions are considered to be a way to move on to a new generation of smart electric networks.

A large number of microprocessor-based devices of relay protection, automation, and communication are used at electrical substations, the resistance of which to electromagnetic interferences is several orders of magnitude lower than that of the traditionally used electromechanical secondary machinery. Therefore, all technical specifications for the design of modern substations include requirements for electromagnetic compatibility, and, during the operation of substations, an examination of the electromagnetic environment is carried out. Methods of providing the electromagnetic compatibility when the substation lightning rod experiences lightning strokes are considered. The optimization criterion is the minimum of pulse overvoltage under conditions of lightning discharge. A new structure of a two-level grounding device providing minimization of the voltage of conducted interferences at the ports of microprocessor equipment when lightning strokes is proposed. This structure also provides latitude of choice in implementing layout solutions on the substation territory, in particular, when lightning rods are placed at distances from the equipment and cable channels that are less than the standard values. This makes it possible to reduce the area of a substation’s territory.