Том 90, № 2 (2019)

Mathematical models of induction machine in polar coordinates taking into account the saturation process of the main magnetic circuit are presented. Software implementations of the proposed mathematical models and numerical investigations of the processes reproduced with their help are performed in the computing environment MATLAB (Simulink application package). Features of program implementation of such models are determined. It is revealed that they accurately describe the processes taking place in the induction machine at the operation segment of its mechanical performance. It is shown that the mathematical models in polar coordinates reproduce the processes taking place in the induction machine with a accuracy that is the same for models written in Cartesian coordinates.

A hardware and software complex for remote monitoring of high-voltage line arresters (HVLAs) under operating voltage has been developed. The complex is a two-level distributed system with autonomous monitoring points. The main functional units of the complex are a block of current sensors, a registration and communication device, a self-contained power supply, a receiving base station, and an automated workplace (AWP). Apart from the total leakage current and number of operations, the complex registers the amplitude and duration of the HVLA lightning pulse. These parameters may be used for the assessment of the HVLA residual resources and making a decision as to the feasibility of its further operation. An optical sensor on the basis of a bismuth silicate crystal is used as a sensor of an impulse current; its operating principle is based on the Faraday linear magnetooptic effect. The advantage of the bismuth silicate crystal is the feasibility of the noncontact measurement of the pulse magnetic field strength, high temperature stability and high noise immunity. The standard of the wireless LoRa communication was selected for the transmission of information; its advantage is a high noise immunity, larger range of radio signal transmission (up to 10 km), low energy consumption, and high penetrating capacity penetrability. A solar battery with a standby power supply—a rechargeable battery—was selected as the self-contained power supply. Program modules for receiving and transmission of information and AWP were developed. The hardware and software system allow preventing the emergency situations on the high-voltage line, planning more service and repair operations more effectively and efficiently, and starting the operation of HVLAs based on technical conditions.

Assessing the state of insulating gaps in the form of particular numerical values may improve the maintenance efficiency of power equipment. This state is considered as a certain energy parameter that represents the amount of energy required to switch the gap into a state of complete failure or into a state wherein its further operation becomes impossible. The sets of electrophysical parameters of the insulating gap, the values of which correspond to its state, are considered as particular functions that underlie the formation of a complex parameter, the value of which is a quantitative characteristic of the state of a controlled insulating gap. The factors that have determined the main issue in assessing the gap state in the form of a structural and logical scheme are the set of possible aging mechanisms and the manifold significance of influencing factors, as well as the representation of the transformer life cycle in the form of a sequence of stages, each of which is characterized by its own aging mechanism and its own type of defect that develops within the insulating gap.

The breaking of soil dams always happens unexpectedly and spontaneously. At the same time, accidents of and damage to pressure head soil constructions or their separate parts are caused not only by the wrong selection of a dam type or a mismatch to their specific conditions of operation or by violations or defects of construction, but also maintenance errors, which, naturally, can lead to negative consequences. When accidents of soil dams happen spontaneously, there is a very short time window for deciding whether to evacuate the population. Therefore, for timely annunciator about emergency situation still topical are the issues of enhancement and development of the modem warning systems in a flooding zone where it is proposed to install information posts, in the lower part of which sensors will be located, and in the upper part there will be an antenna, transmitting a signal to the control desk of a local emergency officer on duty. When the sensor is flooded, there is a short circuit in a circuit and the signal from the transmitter arrives to the control desk of an officer on duty with number of a pole. The officer on duty analyzes data the retrieved, and, if the number of the poles signaling flooding is greater than three, then the emergency officer starts a siren that sends a signal to the system of central alarm and a siren in the inhabited area will signal that there is danger of flooding. This article considers a system that has been developed of an emergency signaler consisting of a primary signaling unit located near a hydroconstruction or possible direction of movement of waterflow and a secondary signaling unit located in the inhabited area at the boundary of possible movement of a break wave, which, through the intermediary of a computer information system, sends an SMS about the presence of a crisis state to subscribers registered in a zone of possible flooding.

The ac frequencies of 50 and 60 Hz, which are accepted in world practice, have not been substantiated technically and economically as the best for all components of the electric power systems, electrical installations and electrical equipment. Moreover, theory and practice show that, for many electromagnetic and electromechanical devices used in aircraft and water vessels, in construction and road construction machinery with motorwheels, in the agriculture industry, in the timber and timber-processing industry, and in other economic and infrastructural spheres, ac overfrequencies (f > 60 Hz) are preferable. Meanwhile, on the one hand, the wide range of frequencies (100–500 Hz) is considered the optimum, and, on the other hand, the cumbersome analytical expressions for substantiation and calculation of specific machines equipped with the electromagnetic devices, normally including transformers and the widely used inductions motors, are proposed. Simplified procedures for the analysis of the effect of ac frequency on the mass and size parameters of transformers and low-power induction motors are proposed in this article. They allow narrowing the optimum frequency range down to 200–400 Hz and obtaining acceptable results from engineering calculations of this effect.

Short circuit (SC) withstand strength is one of the key characteristics that define the reliability of power transformers. The SC withstand strength test methods are stated in State Standards GOST (State Standard) 20243 and 55188 (IEC 60076-5). This work considers problems related to the SC withstand strength test of distribution transformers that are not indicated in these standards. The dependence of SC peak current on average temperature of windings is considered. The possibility of heating of the windings of distribution transformers during the SC withstand strength test and related to it change of peak factor are revealed. The requirements of standards related to the winding temperature when the SC withstand strength test are considered. It is revealed that during the test of distribution transformers, one can expect the deviation of actual peak factor from its designed value by about 5% that should be taken into account when testing and analyzing the test results. The specific of test of the transformers with δ-connected winding is that, as a rule, merely the line currents of this winding can be recorded during SC experiments, at that, there are differences in peak currents for line currents and phase currents of windings. The requirements presented in GOST (State Standard) 20243 and R 55188 (IEC 60076-5) for SC peak current were stated as applied to the phase currents of windings, as well as to the line currents of star-connected windings. The difference of the peak factor for the line currents when testing the transformers with star- and δ-connected windings was revealed in the work, and it was concluded that the abovementioned standards for the requirements and test methods to SC withstand strength of the transformers need to be refines.