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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.

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.