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The article substantiates the need to update the normative documentation for the selection of smoothing devices for DC traction substations. General requirements for smoothing devices, labor protection and electromagnetic safety requirements are formulated. The main schemes of smoothing devices used at DC traction substations are considered. Recommendations have been developed for the selection of smoothing device schemes for the modernization and construction of new traction substations, taking into account their energy efficiency.

The purpose of the article is to consider the issue of calculating and selecting the settings for the operation of the short-circuit switch KZKS-3.3 when organizing the protection of a direct current contact network in emergency mode. The shorting circuit is measured by the voltage module. When the triggering conditions are met, it is the voltage module that collects the circuit to turn on the switching device of the short circuit. The important question is to choose the optimal installation location of the short-circuit switches and the voltage trip settings. The initial information necessary for the calculation of the settings is determined. The calculation procedure and equivalent circuits for the most common power supply circuits and sectioning of the contact network are given. For current protection of high-speed circuit-breaker feeders, contact formulas are given for determining the sensitivity zones. To select the optimal installation location of the short-circuit and select the voltage pick-up setting from the allowable range, a potential diagram of the contact network section is constructed. The analysis based on the potential diagram allows us to conclude that the organization of protection of the contact network in emergency mode using short circuits is effective.

The article considers the issue of providing protection for the contact network when removing 3.3 kV traction substations from the Nazivoye direction of the Omsk power supply distance of the West Siberian Railway. When the 3.3 kV switchgear is brought out to repair, the protection zone for connection of the contact network of adjacent traction power supply system objects (traction substations, sectionalizing stations, parallel connection points) increases. To ensure the protection of the DC contact network, lowered settings for the operation of high-speed circuit breakers are introduced, which inevitably limit the capacity of the section for the passage of freight trains. Considered the existing order of withdrawal of equipment for repair with the inclusion of a traction substation post section. The limitations of skipping freight trains during the implementation of the existing scheme are estimated. Short circuit currents are also calculated and the settings for the protection of high-speed circuit breakers are selected when the sectioning station is switched off and the sectional disconnectors of the station are switched on. It was found that the condition for selecting the protection settings is not fulfilled when detaching from the minimum value of the short-circuit current. To reduce the limitations, a prototype of a short-circuit contactor of a direct current 3.3 kV grid has been developed. The use of a short-circuit-breaker allowed the protection of the contact network, for the time of the withdrawal of the switchgear equipment for repair, without transferring to lower settings for the operation of circuit breakers. Also in the article are given the technical characteristics and features of the proposed device design. The results of a test of a short-circuit of a 3.3 kV direct current contact network in the Dragunskaya-Novokievskaya-Lubinskaya section are presented. The main directions for further work are determined.