Development of methodology for determining a-parameters of an asymmetric rail line

The article considers the methodology of forming the matrix of A-parameters of a rail line, represented by a multi-pole equivalent circuit. It is shown that when using a four-pole equivalent circuit of a rail line in case of violation of the equipotentiality of the circuit, it is impossible to take into account the flow of current along bypass paths, along the earth path, and the influence of adjacent track circuits. A multi-pole equivalent circuit of a rail line is represented as a 2x4 pole, in the rail lines of which self-induction EMF sources are included, and an earth path is used as the second wire. An equivalent multi-pole of equivalent circuit is represented by two groups of poles – at the input and output of the rail line, including one common (ground). The parameters of all elements of the equivalent multi-pole circuit are presented in the form of matrices, which makes it possible to analyze the state of the rail lines when changing the primary parameters of the rail multi-pole in a wide range. Using Kirchhoff's laws and solving a system of ordinary differential equations, the A-parameters of a rail multi-pole are obtained.

THE EFFECT OF FAILURES IN INTERVAL CONTROL SYSTEMS ON THE MOVEMENT OF TRAINS ON DOUBLE-TRACK SECTIONS

The level of reliability of systems for train traffic train separation directly affects the safety and conti- nuity of their movement, the speed and timing of delivery of goods and passengers, the labor intensity and cost of transportation, and the costs of operating these systems. If we consider a section of a railway as a complex dynamic system, then with a relatively small weight of fixed assets of technical means intended for interval regulation of train traffic, failures in them signifi- cantly affect the system output. On the railways of Russia, the systems of interval regulation are mainly used with the use of track circuits and the division of hauls into block. Such systems are widely used on the world’s railways. There- fore, the problem of quantifying losses in train movement from failures of electric interlocking devices while through-working and from failures of automatic blocking devices is relevant. The amount of loss depends on the intensity of failures of technical means and the time to restore their operability, on the intensity of train traffic, the length of block sections, the ratio of freight and pas- senger trains on the section, the speed of their movement according to the schedule and the degree of speed reduction due to failures of the considered technical means Both freight and passenger trains move along sections of the Russian railways, the speeds of which can differ significantly, which also significantly affects the traffic loss from such failures. When calculating, one has to use data on block crossing capacity and the capability of accelerating trains. The calculation results provide the possibility of an objective choice of the type of systems under consideration and the requirements for them in a new design or during their reconstruction on railway sections, as well as the possibility of correct distribution of costs to increase the reliability of the oper- ated systems.

Methods of reception and synchronization of signals of automatic cab signalling

The article discusses the problems of existing methods of receiving automatic cab signalling on railway transport, an original method of receiving and processing data is proposed. The need to solve the problems is due to the requirement of a qualitative improvement in the reliability of receiving codes, and as a consequence, the capacity of existing lines. First of all, this refers to a significant increase in the quality of reception and processing of information flows from rail lines. Today it is difficult to imagine the organization of the movement of rolling stock without relying on automatic block systems with secondary sealing of tonal track circuits by frequency modulation signals or automatic cab signaling without the use of multivalued automatic cab signaling with phase-difference modulation. Taking into account the objective fact of noise emission from the operation of energy-intensive railway equipment and modern locomotives, the issues of reliability and noise immunity of receiving discrete information (including signals of traditional automatic cab signaling) are becoming more and more urgent. Analysis of the reasons for the decrease in the reliability and noise immunity of railway automation and telemechanics systems, and, consequently, traffic safety also comes to the fore.

Evaluation of the Electromagnetic Effect of Traction Rolling Stock on Track Circuits

The regulations regarding railways currently in force in Bulgaria require that each new type of locomotive, to get access to railway infrastructure, must undergo a procedure for checking its electromagnetic effect on functioning of track circuits.The relevant testing was carried out for seven types of AC and DC track circuits and for six types of locomotives intended to be put into operation (five electric locomotives and a diesel locomotive).Schematic diagrams of testing conditions are presented. During the tests the voltage waveform, frequency, and level rates at the terminals of the track receiver (on the track relay coil) were recorded for a free (normal (common) mode) and occupied (shunt mode) track circuit during the action of return traction current of electric locomotives, as well as during the action of impacts caused by operation of electrical equipment located in the body and under the frame of the diesel locomotive.For electric locomotives, the tests were carried out during the shunting of track circuits (of a tested one and of the track circuit adjacent to it), starting from the rest, lowering and raising pantographs. For a diesel locomotive, tests were carried out in a stationary mode, when inner wheelsets shunted the insulating joints of two adjacent track circuits and for different cases of arrangement of the equipment of the relay and receiver ends. During the tests, the state of the armature and contacts of track relays was monitored. The amplitude of the recorded interference was compared with voltage of reliable switching off/ on of track relays/track receivers. It was found that during the shunt mode, the recorded residual voltage in the track receiver under the action of the electric locomotive was 50 or more times lower than the reliable operate voltage and 33 or more times lower than the reliable drop-out voltage of the receiver. For a diesel locomotive, the results turned out to be similar, except for the case of shorter DC track circuits, where the amplitude of the interference was higher, but without a dangerous effect on the shunt mode.Based on the results of the tests, it was established that all types of track circuits used on the railways of Bulgaria are resistant to electromagnetic interference emanating from tested samples of traction rolling stock.

Trends in Improving Sensors for Controlling the Condition of Track Sections

Various principles can be used to implement intelligent track circuits: voltage regulation of the power supply, compensation methods for switching on rail lines and track circuit devices, receiver sensitivity adjustment, comparison of two electrical parameters of one, two, or more track circuits, as well as a combination of these methods. At present, such improvement of track circuits is becoming relevant, which would make it possible to exclude from the circuits one of the most unreliable elements - an insulating joint, use a modern microprocessor element base in devices for monitoring the state of track sections, thus ensure their reliable operation. This will significantly reduce the costs of building and operating interval control systems and increase train traffic safety. These requirements are met by intelligent track circuits, which consider the current value of the insulation resistance, the rate of change of this resistance, and the longitudinal asymmetry.

Calculation of tonal rail circuits with consideration of a complicated waveform

The article deals with the problem of calculating modern audio frequency track circuits, the working signal of which is a frequency-manipulated signal transmitting Bauer codes. Such signals have a wide spectrum, which leads to the error in the calculations performed according to the classical method for a single frequency. Increasing the code transfer rate in order to reduce the response time of track circuits further expands the signal spectrum, which negatively affects the safety of such rail circuits. To determine the width and composition of the signal spectrum, a discrete Fourier transformation is used. The new method of calculating rail circuits proposed in this article allows us to determine the root-mean-square value of the signal at the output of the rail circuit with a known amplitude-frequency characteristic of the rail circuit and the form of a complex signal at the input. The obtained ratio of the root-mean-square signal levels at the input and output of the rail circuit allows us to solve the problem of calculating the operating modes of the rail circuit taking into account its nonlinear amplitude-frequency characteristics and taking into account the complex signal form, including consideration of the specific transmitted Bauer code. This solution allows you to increase the reliability of the calculation of the adjustment tables of the tonal track circuits and, as a result, increase the reliability and safety of their operation.

Identification and Localization of Track Circuit False Occupancy Failures Based on Frequency Domain Reflectometry

Railway track circuit failures can cause significant train delays and economic losses. A crucial point of the railway operation system is the corrective maintenance process. During this operation, the railway lines have the circulation of trains interrupted in the respective sector, where traffic restoration occurs only after completing the maintenance process. Depending on the cause and length of the track circuit, identifying and solving the problem may take a long time. A tool that assists in track circuit fault detection during an inspection adds agility and efficiency in its restoration and cost reduction. This paper presents a new method, based on frequency domain reflectometry, to diagnose and locate false occupancy failures of track circuits. Initially, simulations are performed considering simplified track circuit approximations to demonstrate the operation of the proposed method, where the fault position is estimated by identifying the null points and through non-linear regression on signal amplitude response. A field test is then carried out in a track circuit approximately 1500 m long to validate the proposed method. The results show that the proposed method can identify and estimate the fault location due to a short circuit between rails with high accuracy.