Vol 90, No 9 (2019)

Systems of monitoring railroad sections for freeness, as well as systems of transferring information along the rails to train locomotives and between signal points of automatic blocking, operate in a complex electromagnetic environment, especially in electric propulsion sections. The equipment of these systems is affected by electromagnetic interferences in a multifactorial manner, and the causes of high-level interferences are numerous and often interrelated. The tasks one has to perform while studying the electromagnetic environment are fixing a random interference generation process, processing the array of results, and identifying the causes of interferences. The first task can be accomplished by means of digital multichannel oscilloscope recorders, as well as various kinds of current- or voltage-measuring sensors. Accomplishing the second task depends on the goal and becomes very difficult due to the multifactorial essence of interference generation. The studies were pursued in various conditions, including high-speed Sapsan train traffic sections, subway train traffic sections, and heavy train traffic sections. Mathematical descriptions are derived as the probability distribution density for several kinds of electromagnetic interference.

The main trends of technical development and improvement of dc traction power supply systems are considered. Methods and programs are developed that make it possible to study the electromagnetic processes in rectifier–inverter units of traction substations and the self-excited source voltage inverter of induction traction drive and determine and predict the levels of harmonic components of the current in both dc–ac converters themselves and that in the traction network. This makes it possible to determine the electromagnetic effect of various power semiconductor converters on communication devices and railway automation and ground the choice of circuits and protection parameters ensuring electromagnetic compatibility. Analysis and synthesis of electromagnetic processes and the main characteristics of multipulse converters reveals that 24-pulse rectification circuits with serial connection of three-phase bridges are the most effective for a dc traction power supply system with a 24-kV voltage traction network. The introduction of 24-pulse rectifiers makes it possible to decrease power loss in the traction network and reduce the consumption of reactive energy from the primary power supply system. These rectifiers provide not only an increase the traction substation efficiency, but also refinement of electric energy in the primary power supply system and traction network. The latter makes it possible to use simpler and more economical smoothing filters that ensure electromagnetic compatibility of the new dc traction power supply system with communication devices, railway automation, and other infrastructure.

Providing selectivity of the relay protection of a dc network has always been associated with difficulties in distinguishing between operating and emergency modes, which is especially noticeable in the traction power supply system for an 825-V subway due to the high traffic intensity and the use of electric rolling stock (ERS) with asynchronous traction motors. The practice of calculating protection settings shows that the maximum current protection settings (MCPs), both for an electromechanical relay and for microprocessor terminals, as a rule, are set off from the calculated minimum short circuit currents, which can be lower than the startup currents of the ERS. This practice of calculations and modern conditions of operation of a subway power supply system can lead to false activations, which, in turn, can lead to a rapid loss of the switching capacity of high-speed switches, as well as lead to a delay in train movement. An analysis of the current situation leads to the conclusion that simple types of protection, such as MCPs, cannot provide selectivity of outages. The situation is different with multiparameter protection of the type of protection by current increment (PCI) and current buildup rate (PCBR). The essence of the operation of the PCI and PCBR is based on the analysis of changes in the current graph, which allows determination that is faster, and sometimes more accurate, than MCP, whether or not the change in current is connected with the occurrence of a short circuit. However, taking into account the choice of protection settings for changes in current and its buildup rate requires the calculation of transients. The accuracy of such calculations directly depends on the accuracy of determining the electrical parameters of the traction circuit. In modern conditions of development of measuring and computing equipment, one of the most simple and effective methods of calculation is the method of minimizing the distance between a set function or model and the measured data. It is worth noting that the use of this method directly in the algorithmic part of microprocessor-based protection terminals together with self-learning functions will allow one to automatically select the desired values of the PCI and PCBR settings corresponding to the operating conditions of the traction power supply system.

An approach to designing subway traction power supply facilities with an 825-V traction power system is considered in a general digital model. The continuously increasing passenger traffic in metropolitan cities makes it necessary to build new subway lines and upgrade existing ones, taking into account the compliance with all the standards of ensuring uninterrupted power supply at minimal electric stock (ES) train-to-train spans. The ES is also being upgraded, which includes the commissioning of new-type Moscow cars. To maintain the rates of commissioning new subway lines, the quality of design must be improved and the design process must be relocated to the digital environment. An example digital model (twin) of subway traction power system is exposed, as well as its application to estimating the dynamic behavior of ES.