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The subject of this article is voltage regulation in the traction power supply system. The object is the on-load voltage regulation device (OLTC), which is responsible for regulating the voltage in the contact network by changing the transformation ratio of the power transformer of the traction substation. This device is important for maintaining the required voltage level in the contact network, but when operating in automatic voltage regulation mode, high wear of the OLTC is observed. This is due to the fact that the wear of the device directly depends on the number of switching operations it performs per day. In turn, the frequency of switching operations depends on many factors associated with the traction load. Another problem is the different levels of wear of this device in different sections of the power supply - in sections with a flat track profile and low traction load, the damage to OLTC devices is significantly lower due to rare switching operations to adjust the voltage, and in sections with a complex profile and high load, the OLTC demonstrate extremely low reliability, so much so that the personnel of traction substations turn off automatic regulation and perform switching operations manually. In order to predict the wear of the OLTC devices, it was decided to create a computer model of the traction power supply system, including automatic voltage regulation in the network, and a switching counter As a result of the work done, a computer model of the traction power supply system of the 2×25 kV traction system was created in the SimInTech software package, which shows the operation of the automatic regulation system with a switching counter.

The article considers the problem of assessing the impact of charging stations on the load schedules of transformer substations. The solution of the problem is based on the example of facilities undergoing trial operation in the automotive sector of railway transport. The parameters of the electric vehicle charging station and battery are used for a slow charging option based on an AC charging station and a battery with a rated voltage of 346 V and an energy consumption of 48 kWh. To assess the impact of the charging station operation, the results of the trial operation of an electric vehicle are considered. The assessment was performed for a number of load graph indicators. To consider and evaluate the dynamic processes observed during the operation of the charging station, a simulation model has been developed containing a controlled rectifier converter and a charge current limiter implemented using pulse width regulation. The charging station model has voltage and current level control, which are determined based on factory specifications. The results obtained can be used to evaluate the performance of transformer substation schedules when expanding the charging infrastructure, evaluate electricity quality indicators for various circuit solutions used to regulate charge voltage and current, develop demand management measures in electric vehicle charging processes, and develop recommendations for ensuring electricity quality indicators. The results of the work are an assessment of the effect of the charging station operation on the load schedule of the transformer substation, a simulation model of the charging station for testing control algorithms, battery charging protocols and circuit solutions for current rectification and inversion processes.

The new method of parametrical identification of three winding transformer by using phase domain is proposed. Transformer model represents as lattice equivalent circuit.

Transfer of railway lines on the high-speed movement demands strengthening of traction power supply system.Such strengthening can be carried out on the basis of symmetrizing transformers and coaxial cables use.Means of computer modeling of such networks which can be realized on the basis of the methods developed at Irkutsk state transport university are necessary for the solution of practical application of traction networks with the symmetrizing transformers and coaxial cables.Complex technical solution including both from the designated ways of traction power supply strengthening is of interest. Strengthening provides the additional effects consisting in improvement of electric power quality in the feeding high-voltage networks and not traction consumers' power supply,and also in decrease in losses of the electric power and energy efficiency increase. Results of computer modeling of 2х25 kV traction power supply systems with Woodbridge symmetrizing transformers and coaxial cables are given.Modeling was carried out for three options: traditional scheme of 2х25 kV traction network; traction power supply system equipped with the modified Woodbridge transformers; the complex technical solution which is included the symmetrizing transformers and coaxial cables. Modeling results have allowed the following conclusions: application of coaxial cables promotes increase of contact net voltage; due to use of Woodbridge modified transformers it is possible to lower significantly negative sequence asymmetry factor on high voltage buses of traction substations; the greatest effect takes place at complex use of the symmetrizing transformers and coaxial cables.

The article analyzes the influence of parameters and operating modes of traction power supply system on the value of the useful energy recovery and the amount of electricity losses caused by the energy recovery through the traction power system to various consumers. The amount of energy lost in recuperation determines the degree of efficiency of its use. The approaches to the sequential determination of the recuperation energy efficiency and the calculation of the numerical values of the quantities characterizing the parameters of the traction power supply system, which are necessary for an adequate analysis of the energy distribution flow distribution, are proposed. It is determined that it is sufficient to use the regression analysis method to estimate the influence of the parameters and operating conditions of the traction power system on the energy efficiency of the recovery. The values of the relative resistance of the contact network are calculated depending on the type of the contact suspension, as well as on the traction network supply circuits. It is shown that the parameters and operating modes of traction power supply system affect the losses in the contact network, the losses in rectifier-inverter converters and traction transformers of direct current traction substations, the amount of energy recovery from tires of traction substations, as well as the relative change in losses in the system traction power supply with the use of regenerative braking.

The article presents statistical studies of acoustic control signals when diagnosing power transformers of the railway power supply system. Statistical processing of acoustic monitoring data was carried out on the example of transformers with different levels of insulation condition. Comparisons of histograms of the experimental distribution of amplitudes and dominant frequencies of signals with the nearest theoretical distribution laws, performed in the STATISTICA program according to control data obtained from the automated system. The conducted studies have shown a close correlation of defects registered by the acoustic method with the distribution of signals in the form of laws of distribution of random variables. It is shown that for power transformers with mechanical oscillations, both during the passage of the train and at idle, the distribution of amplitudes and dominant frequencies of the recorded signals corresponds to a uniform law. The distribution of amplitudes and dominant frequencies is not centered around a certain average value. For power transformers containing partial discharges, the cause of which is the deterioration of the insulating properties of the windings under the influence of high voltage, the best approximation, both amplitudes and dominant frequencies, showed the Lognormal distribution. The signals are centered around a characteristic mean value. When the train passes, the acoustic system registers both high-frequency signals from the PD and low-frequency signals from body vibrations. There are two components in the distribution law - uniform and lognormal distribution densities. Thus, by the type of distribution of the recorded signals, their amplitude and dominant frequency, it is possible to determine the presence of a defective state of the insulation of power transformers. The study was carried out with the financial support of the Russian Foundation for Basic Research within the framework of the scientific project No. 20-38-90231.

Single-phase transformer with an additional tap at the middle point of the secondary winding is a very common element in the various electrical circuits, including on-board electric rolling stock. A typical case is powered from the transformer zero full-wave rectification circuit. The aim of the article is to provide a detailed description of the computer model developed by the author of said transformer, built on the basis of a combination of circuit and operational design principles. The proposed model can also be used to describe the process in a single-phase two-winding transformer without additional tap, given the possible connection group I / I-6 or I / I-0. Connection groups can be considered individually for each half of the secondary winding in case of using of additional tap. Shows an example of embedding the transformer model in a more complex computer model of the electric traction DC motors excitation current stabilization system, which includes a computer model of a saturable reactor, thyristor rectifier, system of pulse-phase rectifier control and control loop with a proportional-integral current regulator and boost nonlinearity. Obtained during the simulation graphics excitation current in the field winding of collector traction motor and its reactive component show that the above system of stabilization of the current and its computer model of functional and successfully fulfill their functions: at the downturn of the armature current excitation current is maintained by the growth of the current make-up of excitation control rectifier. The correct operation and ease of use of the developed computer model of a single-phase transformer with an additional tap at the middle point of the secondary winding is stated.

In the paper the device for reactive power compensation for the electric locomotives based on passive adjustable compensator was described. This configuration of the compensator improve the power factor of the electric locomotive in all operational modes and raise value of the power factor to its maximum possible value. The management of the compensator unit is based on the extremum seeking control autonomous voltage inverter. Mathematical modeling of electric locomotive showed increase the power factor to a value of 0,98.

A mathematical model for diagnosing the state of solid insulation of high-voltage transformers based on an informational assessment of indirect indicators, i.e. entropy, for example, by the content of impurities of various gases dissolved in transformer oil, which allows to determine the technical condition without removing the workload. The values of the average information on the working and faulty state of insulation for various types of gas impurities are calculated.

The paper discusses the main limiting factors limiting the volume of transportation of high-volume freight trains. Designated approaches to solving the problems presented by the use of compensating devices. The paper presents the method of selecting installation sites and the power of compensating devices in the traction network, taking into account the growth in traffic volumes, allowing to evaluate the positive effect of the installation of compensating devices on the prospect of increasing traffic volumes. Determination of perspective power consumption is proposed to carry out using power consumption forecasting. To assess the effect of the installation of compensating devices in the traction network, three criteria have been proposed: unloading traction transformers, increasing the voltage level at the consumer, and unloading the power transmission lines.

The article discusses the issue of the fire hazard of the dielectric medium of a transformer (transformer oil), in which, over the period of operation, the characteristics, including fire-hazardous properties, change. The purpose of the work is to study the transformer dielectric medium (transformer oil) for flammability. The article presents the results of laboratory tests of new and used transformer oil to determine the parameters of the ignition temperature and flash point. Statistical data on fires related to electrical equipment are analyzed. It has been established that with prolonged and intensive production, the physico-chemical properties of transformer oil deteriorate. The presented studies confirm that transformer oil can transform from a flammable liquid into a more flammable liquid. Studies to determine the flash point and ignition were carried out using laboratory equipment in accordance with GOST 12.1.044-2018. The reason for this critical transformation is being investigated and a more in-depth analysis of samples of new and used transformer oil is carried out using a Crystallux-4000M chromatograph. It has been established that during the period of operation, transformer oil loses its properties, including an increased fire hazard, namely, the ignition temperature and flash point decrease by 19% and 32.2%, respectively. It has been revealed that due to changes in the chemical structure of the oil, its fire safety index is deteriorating. Attention is focused on the urgency of the problem of timely replacement of transformer oil, as it is one of the main sources of fire danger. Ways to solve it are proposed in the form of: more thorough monitoring of the condition and replacement time of transformer oil.

The issue of designing devices with optimal characteristics of converting an electrical signal and its shape without distortion is relevant when developing a device with small dimensions for electric rolling stock. In this article, the influence of transformer parameters on the form of voltage transmission is considered and recommendations are given on the choice of values of these parameters. This applies to pulse, differential, and low-power transformers. The study of this issue is moving from theory to constructive calculation. In the era of digital twin design, the computational mathematical model of the transformer will allow for a quick decision on compliance with the inherent requirements for the product. Being universal, the proposed model allows performing calculations for any pulse transformer, provided that the appropriate initial data is specified and will allow obtaining an estimated characteristic of the transformer already at the design stage. The study showed the relationship between the transformer design, the materials used for the magnetic circuit and the shape of the output signal. Obviously, the dissipation inductance and the capacitance of the windings are the main parameters that introduce distortion into the signal. Modeling of the winding design and the selection of magnetic alloys or ferrites help to reduce eddy currents in the magnetic circuit, which improves the characteristics of the output signal and reduces the effect of the constant component of the current at the end of the pulse. A transformer model with reduced core dimensions made of steel with a smaller rolled thickness and a homogeneous domain structure, as well as the use of a distributed winding along the core, which has a minimum intrinsic capacitance, had the least effect on the output signal with an acceptable signal distortion of 3 %. The resulting transformer model can be used to create a finished product.

The article presents the results of the studied soils on physical and thermophysical characteristics in the territory of the city of Omsk. The lack of such data can lead to erroneous calculations in the design of ground probes using low-potential energy of the earth. A method for determining the minimum distance between wells is proposed, which allows to eliminate soil freezing and increase the efficiency of heat transformers.

This article is devoted to the investigation of the internal parameters of transformers used for power supply of railway automatic and telemechanic devices. In this paper, the change in the nomogram of the impedance area of a power transformer is considered when changing the parameters of the replacement circuit of this transformer. The possibility of visualizing the change in the parameters of a transformer using the mathematical apparatus of conformal mappings is shown. The nomograms of the input resistance of the single-phase oil transformer are constructed with a change in the value of the insulation resistance and the transient resistance at the junction points. Based on the constructed nomograms, conclusions were drawn on the behavior of the input impedance region of the transformer in various situations.