Vol 89, No 9 (2018)

Traction dc power supply systems with a traditional feed voltage of 825 V are part of the basic transport infrastructure of metropolitan cities. The development of electrified railroads has resulted in the mainstream use of these systems. There are many works about their strengths and weaknesses; however, modern circumstances make it necessary to operate and upgrade these systems, maintain their usability, and improve their efficiency. New rolling stock with asynchronous engines is being launched for subway service with increased loads and travel speeds. In these conditions, one of the main features of maintaining the course of transportation is to guarantee uninterrupted power supply of electric rolling stock. This can be made possible through appropriate and timely responses by maintenance personnel, power dispatchers, automation and emergency control systems. The microprocessor systems used at the modern level of technological development have been embodied in intelligent terminals of feeder lines of electric traction networks used in subway service. Their algorithmic part must be improved and upgraded for compliance with the current realities of subway service by integrating emergency control equipment algorithms, full-scale analysis of analog processes in the electric traction network, discrete signals of automatic controls and telemechanics, and states and switches of cross-connect equipment, which must facilitate increased automation of the traction substation and make it completely unattended.

Two blocks were commissioned of an RZhFA-6500 reactor as part of the two-link smoothing device at the Letnaya traction substation of the Sverdlovsk Railroad. To test the efficiency of the reactor, a forced short circuit experiment was performed without stopping the movement of the electric vehicle over the section, the level of psophometric voltage on the dc buses of the traction substation was measured and an experiment was carried out of a forced short circuit with cessation of movement over the section. During the experiments, oscillograms of transient processes were taken, analysis of which confirmed the efficiency of the new type of reactor in the structure of a two-link filter device.

A model for measurement of objects of testing that have a long duration is considered. The model comprises a sequence of operations that need to be performed on the object of testing to measure actuation or release voltages. At the first stage, test controls with various parameters are launched in the model to determine preliminary points based on which the dependence of actuation or release voltage changing is constructed. The value of the control signal is then substituted for this dependence, and the desired voltage actuation or release is derived. The model construction is based on the use of series. The form of the support function is chosen, all the terms of this transcendental function are found, the left side of the function contains preliminarily obtained results of the effects of the test control signals, and the desired coefficients and control signals are on its right side. The form of transcendental functions as fractionally rational series is defined in the model, since it is best to construct the dependence shape using these functional series. The solution of the support function is based on matrix computation using the Gaussian method for normal and overdetermined systems and the Cauchy theorem for multiplication of polynomials. The implementation of the model made it possible to halve the measuring time of actuation and release voltages compared with the commonly used testing technique of a relay of the first class of reliability.

Up to half of failures in the operation of rail circuits and automatic locomotive signaling at the sections of railways with ac electric traction occurs due to the disturbances caused by the traction current asymmetry in the rail lines. Since the primary source of this asymmetry is the asymmetry of resistances of rail threads within the rail circuits, the measurements of the resistance of elements of each rail thread make it possible to not only define the traction current asymmetry, but also to find the elements, the resistances of which go beyond the limits of the norm. The traction current asymmetry can also be measured directly; however, the measurement results depend as well on the conditions of their being carried out—on the temperature of rails and the magnitude of alternating traction current in them. This is explained by the fact that the asymmetry of resistances of rail threads of rail line is formed owing to an asymmetric increase in them in the transient electrical resistances in the joints of rail links and in the choke bridges. These transient resistances depend on ambient temperature and traction currents in rail threads slightly. As a result, when decreasing the temperature of the rails of P65 type from +40 to –40°C, the asymmetry of resistances of rail threads taking into account their mutual inductance increases by 2.2—2.4 times, while increasing the traction current in rails, for example, by three times causes almost the same asymmetry increase. The influence of mutual inductance of rail threads with the contact wire leads to a decrease in the traction current asymmetry in the rail line. The mutual inductance of rail threads with high-voltage lines of longitudinal power supply that are placed on the contact line supports can increase or decrease this asymmetry, depending on which of the rail threads has less resistance. All these factors should be taken into account both when measuring the asymmetry of resistances of rail threads or the asymmetry of alternating traction current in them and when extrapolating these data to other operating conditions of the rail traction network by the rail temperature or by the magnitude of currents in rail threads, contact wires, and high-voltage lines.

A review has been carried out of methods for increasing the energy efficiency of automatic control over the movement of subway trains: choosing an energy optimal sequence of train control modes, distributing the travel time along the line for travel times over the sections between stations, and using the regenerative braking mode. The results of a study related to the influence of the automatic control system on the energy consumption for traction by train are presented. An analysis of the effect of the increase in the time of impact braking in conditions of different types of sections between stations on additional energy consumption at a given train travel time over the section between stations both in the absence and in the presence of a regenerative brake was carried out. The requirements for the path correction sensors, which should provide the necessary accuracy of the train positioning during intense braking, are formulated. A comparison of corrective sensors based on infrared signals and RFID sensors is made. The effect of changing the travel time on the section between stations in order to compensate for the discrepancy between the planned and executed traffic graphs for additional energy consumption was analyzed. In conditions of intense traffic, the requirements for the permissible error in the execution of a given train travel time over the range are ±2.5 s.

An analysis of the characteristics of the output filters of electromagnetic compatibility of a frequency converter, including their logarithmic amplitude-frequency characteristics, is carried out by mathematical modeling. The filters with the different parameters, are considered in the steady operation mode at the carrier frequency of pulse-duration modulation of 2.5 kHz and basic frequency of supply voltage of the asynchronous motor of 50 Hz, including with the different connection diagrams of the damping resistors—with parallel connection of inductance in the longitudinal filter branch and series connection of the capacity in the transverse filter branch. In addition, the filter is studied, not including the damping resistors. The losses in the filters are considered. A conclusion is drawn that it is necessary to consider the parasitic parameters of the capacitors: equivalent series inductance, equivalent series resistance, equivalent parallel resistance considering the leakage current through the capacitor, and voltage regulator diode simulating the behavior of the capacitor under the overvoltages.