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The use of twelve-pulse rectifiers instead of six-pulse rectifiers leads to increased efficiency and efficiency of traction substations of the underground. On the basis of experimental research and analysis of circuit solutions, the conclusion is made about the advantage of a twelve-pulse rectifier circuit of a serial type over parallel-type circuits. The use of rectifiers with a parallel type circuit is possible only if there is an equalization reactor, without which technical and economic indicators are reduced. The introduction of the most rational twelve-pulse bridge rectifier schemes of the sequential type can be carried out by upgrading the installed equipment, or by industrial development by manufacturers of dry transformers with different typical power and rectifiers with tablet avalanche valves with coolers based on heat pipes.

According to electric calculations, the overhead system and power lines being the part of the railway power supply are distributed parameters circuits. Wave processes in the overhead system have a negative impact on the power supply lines, laid in the vicinity of the railway, and increase the power losses in the traction power supply system. For the study of wave processes the method of mathematical modeling of non-sinusoidal signals transmission to the uniform two-wire distributed parameters line is provided. The mathematical model is based on the well-known line differential equations (telegraph equations) using Fourier series. The power line is a three-wire line. The paper presents an algorithm to bring the power line equations to the form of two-wire line equations. To assess the correctness of the mathematical model the research was carried out on the physical model of the line. Using the mathematical model there were given the findings of distributed parameters circuits various modes. The proposed method of mathematical modeling of different shape signals transmission to the distributed parameters line adequately reflects the phenomena occurring in the line and can be used for the analysis of electromagnetic processes both in the overhead system and power lines.

The analysis of wave processes in the system including electric transmission lines, traction substations, AC traction network and electriclocomotives is necessary to accurately assess to energy performance of its work. This system contains concentrated and distributed parameters, consequently the analysis of such a system is difficult and the rolling stock which is also a part of this system represents a dynamic load. The proposed mathematical model of the alternating current traction power supply system allows us to consider electromagnetic processes at its various points taking into account wave processes.

Various converters are operated at electric railways traction substations whose rectifiers design includes plug-in power rectifiers and pill ones. Such a variety of rectifiers design causes the problem of the power supply reliable operation unavailability both of volumes and of quality information concerning the characteristics and diagnostic parameters of power semiconductors rectifiers. For a possible prediction of the diodes and thyristors proper operation, new instruments as well as simple technologies of the preventive diagnostics, correspondent to the state and industry standards and instructions should be developed. One of the most accurate methods to determine not only the serviceability of rectifiers but also to forecast their wear - life, is the diagnostic method of recurrent peak backward current. This method is the basis for the design of a peak backward current meter which is used on the Western-Siberian railway. Using this device the screening of about thirty thousand rectifiers was carried out which resulted in the sorting of out-of-work rectifiers, predicting long term rectifiers conditions. The statistical analysis of the research allowed to determine the number of measures to improve the reliability of traction substations converters.

The article deals with the introduction of a twenty - four pulse rectifiers with various rectification circuits on direct current traction substations. The results of the operation of a twenty-four-pulse rectifier installed at one of the traction substations prove the expediency of using such a converter. The variants of the existing equipment modernization, which is a part of the six- and twelve-pulse rectifiers in order to use it in the creation of twenty-four-pulse rectifiers, as well as the requirements for the creation of such rectifiers in industrial design are given.