Track Circuit Research Articles

Single-Phase Current-Source Active Rectifier for Traction Applications: New Control Strategy Based on Phase Shift Controller

This paper deals with the single-phase current-source active rectifier dedicated for reconstruction of older types of d.c. machine locomotives operating on both a.c. trolley wire voltages of 25 kV/50 Hz and 15 kV/16 2/3 Hz. This contribution presents new control strategy of the current-source active rectifier using controller of phase shift angle (φ) between the trolley wire voltage and current. Regarding possible interaction with railway track circuits and due to the low switching frequency, the converter employs synchronous PWM. This paper describes in detail proposed converter control and presents simulation results of the laboratory prototype. The simulation results and theoretical conclusions are verified by experiments performed on designed low voltage laboratory prototype of traction current-source active rectifier of rated power of 7 kVA.

354018 DEVELOPMENT OF A TRAIN APPROACH ALARM SYSTEM WITH GPS-LINKED MOBILE PHONES(Safety,Technical Session)

To prevent such dangerous situations, as the workers on the track are exposed to the risk of being hit by an oncoming train, JR West has developed and implemented a GPS-linked train approach alarm system and put it in practice. Under this system, each train lookout carries two mobile phones that automatically measure their position through the Global Positioning System (GPS). The phones trigger a train approach alarm attached to them if a train is detected on the track circuit specified in advance for each work site.

THE FUNCTIONAL ANALYSIS AND SYNTHESIS OF THE CRITERIA FOR DANGEROUS FAILURES OF RAIL CIRCUITS OF VARIOUS TYPES

In the paper the criteria of dangerous refusals of track circuits of different types are complemented by the time features.

Upgrade of signaling system on the rapid transit systems

In this paper, discuss the upgrade system for an old type and extend to new line system of signaling at Taipei Rapid Transit Systems (RTS). Since the track circuits of fixed block are utilized the ...

Design of Low Power Track and Hold Circuit Based on Two Stage Structure

This paper proposes a low power and high speed track and hold circuit (T/H circuit) based on the two-stage structure. The proposed circuit consists of two internal T/H circuits connected in cascade. The first T/H circuit converts an input signal into a step voltage and it is applied to the following second T/H circuit which drives large load capacitors and consumes large power. Applying the step voltage to the second T/H circuit prevents the second T/H circuit from charging and discharging its load capacitor during an identical track phase and enables low power operation. Thanks to the two-stage structure the proposed T/H circuit can save 29% of the power consumption compared with the conventional one. An optimum design procedure of the proposed two stage T/H circuit is explained and its validity is confirmed by HSPICE simulations.

Design of a 1-V 1-MS/s Track&Hold circuit based on the switched opamp approach

A very low voltage solution for the realization of the hold capacitor in a Track&Hold circuit based on an open-loop architecture is introduced. The circuit is a modification based on the switched opamp approach of the Track&Hold circuit using Miller Capacitance. Simulations show that the circuit is able to operate at 1V 1MS/s with a Total Harmonic Distortion of −64 dB @ 100 kHz and a very low power consumption of 80 µW.

Study on Quantifying and Reducing Electrical Resistance between Wheels and Rails

The train-detecting track circuit currently used is dependable and has the characteristics required of a railway signalling system in terms of economy, continuous detection, etc. However, when rails become rusty, the shunt resistance becomes higher, making it difficult for the track circuit to detect trains precisely. We have therefore researched shunting malfunction to enable the proposal of a new countermeasure against the phenomenon. In this paper, we describe the measurement and analysis of environmental conditions and resistance. We then show the results of these experiments, and propose that shunting malfunction is a problem of railway systems as a whole that should be addressed through the adjustment of the various conditions involved.

Advancement of Analysis Method for Electromagnetic Screening Effect of Viaducts for Railway

New method to estimate electromagnetic screening effect of rigid frame viaducts has been developed. Mutual relationship among the effects of electrical connecting manner of girding bridges; conductivity of the ground; and harmonic frequency was identified theoretically and numerically based on the results of multiple conductor circuit model simulations and field measurements using over 3km length test cables set on a viaduct section of Shinkansen line under construction. Adding, developed modeling method to simplify the equivalent circuit of vast amount of steel bars in the reinforced concrete accelerates the estimation process with enough accuracy. As the result, it became easy to calculate the induced voltage in the cables or in the track circuits with enough accuracy.

Development of Lightning Surge Sensor for Railway Signal Electronics

We have developed a new railway signal control system, which controls railway signals, switches, track circuits based on IP protocol. In this system, much electronic devices are installed along harsh railway environment. Therefore, it is required that these electronic devices have environment resistance for lightning surge, temperature, vibration, waterproof and electromagnetic noise. As a countermeasure for the lightning surge, we utilize a protective device (cable arrester). However there is a case in which the electronic device is damaged by the degradation of the protective device. Therefore we develop a lightning surge sensor to detect the degradation of a protective device. In this paper, we describe details of the lightning surge sensor for railway.

Analysis of Input Impedance of the Traction Vehicle with DC Chopper as a Function of Operation Mode

A problem of analysis of the input impedance of a converter traction vehicle is presented in the paper. The value of input impedance of a traction vehicle has significant influence of compatibility between track circuits and traction vehicles. The model of chopper controlled DC series motor vehicle was implemented as a simulation model including all significant parameters of the whole system: substation-catenary-input filter-chopper. Exemplary results of analysis of the specific locomotive EM10 are included. The results both of analytical and simulation approach for low frequency input impedance computations were compared.

Fault detection and diagnosis for railway track circuits using neuro-fuzzy systems

Railways are expected to operate with ever increasing levels of availability, reliability, safety and security. One way of ensuring high levels of dependability is through the use of condition monitoring systems. This paper presents the results of research on fault detection and diagnosis methods for railway track circuits. The proposed method uses a hybrid quantitative/qualitative technique known as a neuro-fuzzy system. Such a hybrid fault detection and diagnosis system combines the benefits of both fuzzy logic and neural networks, i.e. the ability to deal with system imprecision and to learn by neural network training processes. It is shown that the proposed method correctly detects and diagnoses the most commonly occurring track circuit failures in a laboratory test rig of one type of audio frequency jointless track circuit.

Reliability analysis of track circuit of Indian railway signalling system

This paper deals with the reliability modelling of one of the vital subsystems of railway signalling, called track circuit. The track circuit, a complex repairable system, is used to identify the occupancy of a portion of railway track by a train. It is observed that operations of track circuit are affected by a number of problems in relation to its intensity of use, repair and maintenance and environmental stress. Keeping in view its operating efficiency to the effect of these problems, the recommended parametric model based on repairable system technique is applied to estimate the failure rate probability of the system. Two graphical methods, viz., Nelson−Aalen and Total Time on Test (TTT) plots, are used to analyse the trend of the failure time data for a set of representative track circuits in Kharagpur Division of Indian Railways. Finally, the intensity function of the track circuit is assessed and investigated.

Wide-range single-ended CMOS track-and-hold circuit

This paper investigates the performance of a MOS track-and-hold circuit as the front end of a wide input range and high-speed single-sided ADC. In order to reduce charge injection and clock feedthrough errors, a new technique for employing a dummy transistor in the bootstrapped switch of the track and hold circuit is introduced. Performance of the proposed circuit for the two cases of constant and non-linear hold capacitor is studied. It is also shown that how and when dummy switch and bulk switching method can improve the accuracy of the T/H.

Static wheel/rail contact isolation due to track contamination

An experimental study has been carried out to investigate the effect of contaminants such as sand and leaves on the electrical isolation of a wheel/rail contact. Train detection, for signalling purposes, can be by means of track circuits. Signalling block occupancy is triggered by the wheelset of the train ‘shorting out’ the track circuit. Contaminants in the wheel/rail interface mean that contact between the wheelsets and the track may be compromised, inhibiting train identification. Tests were performed using sections cut from wheels and rail sections loaded together hydraulically with different combinations of contaminants in wet and dry conditions. The electrical circuit used was a simplified simulation of the TI21 track circuit. The sand results indicated that a transition exists in the amount of sand in the contact above which isolation occurred. This amount is higher than the specified sand application rate for train operation at 4.5 m/s (10 mile/h), much of which will not actually make it into the contact. At lower speeds, down to zero, however, if the applied sand rate is not reduced, there is a possibility that this amount could enter the contact leading to isolation. Dead leaves were found to present the greatest problem in terms of isolation. The addition of sand used to mitigate the problem of adhesion loss caused by leaf fall made the likelihood of isolation greater. With water, breakdown loads were lower and partial conductance was seen to occur, although it is not clear whether these levels of conductance could be detected by a track circuit. This needs further investigation. Leaves with a higher level of sclerophylly (leatheriness) were found to be harder to break down. Loads used represented an average value for the tread contact. It was clear that for tests with dead leaves, particularly, the breakdown loads were around this level. With train masses gradually reducing leading to lower wheel/rail contact forces, the problem could get worse. At the present stage of development, the test method is best used as a means to qualitatively assess relative effects on electrical isolation of different contaminants, but can provide information that may be able to help in assessing where greater attention to leaf clearance may be necessary.

A Development of the High-capacity Data Transmission System on Track Circuit Using Spread Spectrum Communication

This paper describes the high-capacity data transmission system for advanced ATC (Automatic Train Control) System on track circuit. A conventional ATC system is very high safety, but this system has not realized the high-capacity data transmission because of the high return current noise. Therefore, we develop the high-capacity data transmission system using spread spectrum communication in consideration of the characteristic of track circuit. And we verified to be able to take about 2000 bps, with the result that we carried out computer simulations changed the transmission speed about this system. In addition, we studied about the method of a synchronous acquisition. As a result, we established a good method by giving the same data for a synchronous acquisition to some channels. We report this method with result of computer simulations.

A Study on Railway Signal System to Apply CDMA-QAM Method

Recently, QAM (Quadrature Amplitude Modulation) transmission is paid to attention in digital modulation method, and it has been used for wireless LAN and digital broadcasting. QAM is a modulation method that puts information on carrier amplitude and phase. So QAM can achieve high-capacity data transmission that the use efficiency of frequency band is good. But QAM has a bad characteristic that is weak to the noise and the interference because distance between each symbol is short. Then we propose the method that not transmission data but CDMA signal, obtained after transmission data is modulated by spread code and multiplexed, is given to each symbol of QAM. And we studied about railway signal system on track circuit as a sample to apply this method. As result of computer simulations, we verified to be able to achieve the improvement of signal to noise ratio by optimizing the constellation map of QAM. We report with the method of a synchronous acquisition.

NEURO-FUZZY FAULT DETECTION AND DIAGNOSIS FOR RAILWAY TRACK CIRCUITS

Railway track circuits are used throughout the world as a basic component in safety critical signalling systems to detect the presence of trains. One way to ensure that railways operate with ever increasing levels of availability, reliability, and safety is through the use of intelligent condition monitoring systems to support maintenance activities. This paper presents the results of research on fault detection and diagnosis methods for railway track circuits. The proposed method uses a hybrid quantitative/qualitative technique, known as a neuro-fuzzy system. It is shown that the proposed method has the potential to detect and diagnose the most commonly occurring track circuit failures.

System analysis of train operations and track occupancy at railway stations

A system analysis approach is presented for investigation of train operations in railway stations based on network, timetable and train detection data. The estimated blocking times, buffer times and track occupancies are compared with real operations data recorded automatically by track circuits. Statistical analysis of train operations between two Dutch major railway stations in The Hague clearly reveals that the trains operate at lower than design speed and the capacity of the critical routes to/from the platform tracks via level crossings is occupied up to 80 %. Furthermore, the dwell times at platform tracks are systematically extended due to hinder by other trains and behaviour of railway personnel. The scheduled headway between arrival and departure of some pairs of trains at critical route nodes proves to be insufficient, because the scheduled dwell times at stations and running times at junctions are generally exceeded and often leads to route conflicts if the headway times are short. The quality of timetable design and train operations in stations would be improved significantly if the feasibility of the scheduled arrival and departure times at major transfer stations was proven by a detailed estimation of the blocking and buffer times based on observed running times and delays during operations. The buffer time at junctions and level crossings should reflect the distribution of real train speeds and blocking times.

Study on centre-fed boundless track circuits

An equivalent circuit diagram for a track circuit with one transmitting end and two receiving ends is presented. Two-port network models are developed under normal, shunt and broken rail modes of operation. Shunt sensitivity and broken rail sensitivity are studied in relation to each of the receivers. An abstract synthesis algorithm is devised and used to determine the optimal end-input impedances. The maximum length of the boundless track circuits of the Sofia Underground is determined.

Influence of Contact Condition Between Rails and Wheels upon Track Circuit Shunting (4th Report, Result of Continuously Measured Shunting Resistance of the Running Wheelsets)

To investigated an inadequate track circuit shunting phenomena which rarely causes a serious railway accident, authors stuck bio-electric amplifiers on the wheel sets' axles of an experimental model truck. They operated the truck on an experimental model test track which was setup with a new conception so as to constantly keep the applied voltage to the wheelsets of the truck. Using the bio-electric amplifiers, the shunting circuit resistance of the wheelsets was continuously measured by the minute difference voltage induced in the wheelset. They investigated the relation ship between the running surface of rails and wheels and the shunting resistance. As the results, they found that the surface roughness of the wheel in a minute scale was radically decreased according to the running distance and that the resistance was simultaneously increased.