Running Rails Research Articles

Grounding Fault Diagnosis of Running Rails Based on a Multi-scale One-Dimensional Convolutional Neural Network in a DC Subway System

Running rails are the return conductors of the traction current in DC subway systems, which should be insulated from the earth. Due to the large length of the line, as well as the humidity and metal dust in the tunnel, grounding fault of the running rails usually occurs, which will increase stray current (SC) leakage and endanger power supply safety. In this paper, a method of grounding fault diagnosis of running rails based on a multi-scale one-dimensional convolutional neural network (MS-1DCNN) is proposed. Firstly, a platform for the dynamic distribution of SC and rail potential (RP) with grounding faults existing in the running rails is established, which generates the dynamic RP data with various grounding faults. Secondly, a grounding fault diagnostic method of running rails based on MS-1DCNN is proposed, so as to realize the effective identification of ground fault types in subway systems. Thirdly, with the proposed diagnostic method, the datasets under two operating conditions of a single train and two trains are tested; a comparison test between MS-1DCNN and the 1D convolutional neural network (1DCNN) is carried out, and the effectiveness of the proposed method is verified. Results demonstrate that the proposed model can significantly improve the ground fault diagnostic accuracy of running rails. The dynamic RP simulation platform for trains established in this paper lays a theoretical foundation for the grounding fault research of running rail. Moreover, the deep learning method is proposed for the first time to diagnose the grounding fault of running rail, and the high diagnostic accuracy is obtained, which is of great significance for the safe and stable operation of the subway line.

Enhancing RCF rail defect inspection on the Serbian railway network

The interaction between the wheel and the running rails within the railway system introduces intricate stress patterns, resulting in the formation of rolling contact fatigue (RCF) rail defects. The magnitude of this stress is contingent upon factors such as track performance, vehicle characteristics, and service conditions. While advancements in rail metallurgy can mitigate the issue to some extent, no economically viable steel composition currently exists that can completely withstand the repetitive stresses associated with RCF. It is more cost-effective to properly maintain rails for longer use rather than replace them entirely. The paper emphasizes the importance of classifying and coding RCF rail defects in light of their potential adverse effects on rail transport safety. It provides an analysis of the available inspection methods for RCF rail defects and recommends the ones that should be implemented on the Serbian railway network. A combination of proposed inspection methods is preferred to increase detection efficiency for different types of RCF defects.

Towards understanding of corrosion behaviors of Q235A pipeline steel subjected to simulated direct stray current interference in different electrolytes

Electrochemical corrosion induced by leakage current from the running rail in DC subway system, the stray current corrosion, is a threat that can't be ignored to the transportation pipeline near the metro line system. In view of the corrosion problem caused by stray current in the subway, this paper discusses the evaluation of simulated direct stray current interference on Q235A metal in two types of electrolytes (solution or soil environments), which is often employed as the pipeline steel. Instrumental methods employed in this study to conduct the electrochemical analysis includes Tafel polarization, electrochemical impedance spectroscopy, SEM scanning and EDS scanning to analyze the main electrochemical parameters for the assessment of corrosion resistance during the stray current corrosion process, which is carried out in electrolyte solution and soil environment, respectively. The EIS of electrolyte solution and soil environment (10 min–30 min) exhibits the same equivalent electronic circuit. The electrochemical results were also compared with two different experimental environments to exhibit a degree of similarity. Results also show that the charge transfer resistance Rct decreases and corrosion current density icorr increases in both electrolyte solution and soil environment, which indicates a reduction of corrosion resistance during the experimental period of this study.

Establishment of aerodynamic force model with varying wind yaw angles and its influences on the safety and comfort of the rail vehicle

Taking the CRH2 rail vehicle as the case study and combined with the pressure measurement test method, the influences of different wind yaw angles (β) on the pressure distributions and aerodynamic coefficients of the rail vehicle were analyzed, and the contributions of each part of the rail vehicle surface (windward, top, leeward, and bottom) to the three-component coefficients of the rail vehicle were investigated. Significant differences in the aerodynamic coefficients of the rail vehicle between the results obtained from the traditional sine rule and those from the test results were found. Then, the expressions of modified sine rule model for the aerodynamic coefficient of the rail vehicle under the whole β of 0°–90° were proposed, and the buffeting force model of the running rail vehicle was established. Finally, the influences of the aerodynamic coefficients based on the modified sine rule and the traditional sine rule on the safety and comfort of the running rail vehicle were comparatively studied by using the SIMPACK multi-body dynamics software. The results showed that when the β∈[45°,50°], the curve-fitting expression for calculating the mean pressure coefficient (Cp_mean) on the rail vehicle surface has the same format as that for calculating the RMS values of fluctuating pressure coefficient (Cp_rms). The aerodynamic coefficients of the rail vehicle obtained by using the traditional sine rule are significantly smaller than the test values at the different β. The overall fitting accuracy of the drag coefficient of the rail vehicle by the modified sine rule model is the highest at the β of 0°–90°. It was found that wind loads of the rail vehicle are independent of the vehicle speed under the β of 0°–20°. The dynamic responses of the rail vehicle calculated by the modified sine rule are always greater than those calculated by the traditional sine rule at different wind speeds and vehicle speeds, and the traditional sine rule will lead to unconservative or unsafe conclusions on the operation safety of the rail vehicle.

Severe rail wear detection with rail running band images

AbstractRail wear occurs continuously owing to the rolling contact load of trains and is fundamental for railway operational safety. A point‐based manual rail wear inspection cannot satisfy the increasing demand for rapid, low‐cost, and continuous monitoring. This paper proposes a depth‐plus‐region fusion network for detecting rail wear on a running band, which is a collection of wheel–rail interaction traces. The following steps are involved in the proposed method. (i) A depth map estimated by a modified MiDaS model is utilized as guidance for exploiting the depth information of the running band for rail wear detection. (ii) The running band of a rail is segmented and extracted from images using an improved mask region‐based convolutional neural network that uses the scale and ratio information to perform instance segmentation of the running band images. (iii) A two‐channel attention–fusion network that classifies rail wear is constructed. In this study, we collected real‐world running band images and rail wear‐related data to validate our approach using a high‐accuracy rail‐profile measurement tool. The case‐study results demonstrated that the proposed method can rapidly and accurately detect rail wear under different ambient light conditions. Moreover, the recall rate of severe wear detection was 84.21%.

High Voltage DC Auto-Transformer Traction Power Supply for Braking Energy Utilization, Rail Potential, and Stray Current Mitigation

For urban rail transit, high-voltage ac power is generally transmitted from the main substation to the traction substation (TS), which employs isolated diode–rectifiers to feed the dc traction power supply system. The train current feeds back to the negative cubicle of TS through the running rail, which is not totally isolated from the Earth. However, the traditional traction power supply (TTPS) shows limitations on braking energy-wasting, high rail potential, stray current, and so on. Thus, a high-voltage dc autotransformer (DCAT) traction power supply (HDATPS) is proposed in this article. Both configurations and principles of three typical HDATPSs are analyzed, which mainly consists of the dc main substation, the dc TS, and the DCAT substation. Then, through modeling of HDATPS and TTPS, the comparisons on braking energy utilization, rail potential, and stray current mitigation are discussed in detail. Finally, the simulation model and experimental platform of HDATPS are built, respectively, and the theoretical analysis is verified with the simulation and experimental results.

Evaluation of rail potential and stray current reduction by using NEG-ETP in DC railway system

The NEG-ETP system that providing zero resistance closed circuit reducing the reverse path of current on the running rail is presented in this article. The NEG-ETP system is created by installing additional electronics in conventional electrical systems. Without modifying trains, tracks, or tunnels. Using MATLAB program through models for MRT purple line (North), rail potential and stray current are assessed in accordance with EN 50122 standards of all three systems, including CON-ETP, REC-ETP, and NEG-ETP. According to the simulation, the percentage reduction of the rail potential was 9.14% when the REC-ETP versus the CON-ETP system was 32.99% when the NEG-ETP system compared to the CON-ETP system and 26.25% when the NEG-ETP system versus the REC-ETP system could be seen in this negative resistance converter system, which can reduce the cost of rails and leakage currents in the DC system. It can also be applied to new rail transport.

Improved control strategy of zero-resistance converter system for rail potential and stray current mitigation

ABSTRACT In urban rail transit, the running rails are generally employed as the traction current return path, which inevitably causes rail potential and stray current issues. As one of the solutions, zero-resistance converter system (ZRCS), consisting of negative resistance converters and switch units, establishes zero-resistance loops to shorten the return loop of traction current in running rails, so as to mitigate rail potential and stray current. Considering the defects of accumulated detection errors by multiple voltage sensors in traditional control strategy (TCS), an improved control strategy (ICS) taking rail potential at specific points as control objects is proposed. Furthermore, based on mathematical model of ZRCS, the rail potential and stray current distributions under different control strategies are discussed. Compared with TCS, the ICS enhances ZRCS rail potential and stray current mitigation performance. Finally, the feasibility and effectiveness of the ICS are validated through experimental verification.

Оценка влияния электромагнитной обстановки многопутных участков железных дорог на функционирование приемников сигналов автоматической локомотивной сигнализации

Increasing the interference immunity of automatic cab signaling receivers of the main locomotive safety devices using the path-locomotive inductive communication channel is a complex task which, in particular, can be solved by assessing the degree of influence of individual factors leading to equipment malfunctions en route. The present work is devoted to assessing the effect of asymmetry arising under the action of traction current flowing in the rail threads of adjacent tracks on multitrack sections of railways. Based on the Bio - Savard - Laplace law, a system of equations has been compiled to calculate the value of the asymmetry coefficient at the input of the cab receiver. The resulting system takes into account the asymmetry in the rail line of each of the tracks, displacement of the receiving coils relative to the axes and levels of the heads of the corresponding running rails. The analysis showed that in conditions of the receiving coils geometric position asymmetry, the asymmetry at the input of the cab receiver when moving along a multi-track electrified section can be five percent or more. In case of placing test sections of automatic cab signaling check-points on tracks adjacent to tracks intended for passing trains, the asymmetry coefficient at the input of the cab receiver reaches forty percent, which can lead to significant distortions of the results of the tests. The proposed equation system and the results obtained can be used to analyze the electromagnetic situation on multi-track sections of electrified railway lines.

Gauss pseudospectral‐based velocity optimization for rail transit trains with running and computation delays

AbstractWith the progress of urban intelligent construction, urban rail transit trains have become one of the most important ways for urban traffic. Optimization operation is a key to further improve the performance of urban rail transit. In this work, an energy saving velocity planning algorithm for rail transit train with running and computation delays is proposed. First, an optimization model with considering both running and computation delays is established for velocity planning. Then, the velocity planning algorithm frame is proposed based on Gauss pseudospectral distribution, where the running delay and computation delay are tackled separately. Meanwhile, the gradient information of transform nonlinear programming (NLP) problem is derived in detail so that NLP solver can be employed to obtain accuracy results. Furthermore, the implementation steps of the proposed algorithm are given. Finally, simulation tests are carried out on a two‐station running rail transit train model with three different delay situations and two different slopes railway. Numerical results and comparison show the effectiveness and correctness of the proposed method for rail transit train velocity planning with delays.

On the issue of improving the methodology for confirming maximum safe (design) speed of freight railcars

The article provides the analysis of regulatory documents and scientific publications concerning the design speed of rolling stock. The material is provided from the perspective of a methodological approach to establishing the design speed at the level of the maximum value achieved during dynamic and strength tests and track impact tests of the object that meets requirements of technical documentation. Values of strength and dynamic properties of cars obtained during tests performed in track sections with characteristics established in test methods should comply with requirements of regulatory documents. At the same time, during the operation of car running gear, rail geometry and track superstructure, basically have a state that is different from that in which tests were performed. Proceeding from this, in order to ensure traffic safety in operation, permissible speeds are set for tracks of various states and structures. Thus, for freight cars with three-piece bogies, the maximum speed, especially when empty, is limited due to the deterioration of its dynamic properties associated with change in the operation of design parameters and characteristics of bogie elements as well as its rigidity couplings. Due to the deterioration of dynamic properties , the design speed cannot be implemented, including on the track that meets requirements of test methods, on which it was initially confirmed. The maximum permissible speeds of freight cars that are acceptable from the safety point of view are traditionally established based on the results of tests performed since the middle of the last century. When applying innovative freight cars with bogies of a new design, to assess traffic safety, it will be necessary to carry out a large number of tests and to gain operating experience, during which it is necessary to estimate the influence of various factors on traffic safety. In fact, it is necessary to repeat tests to set running speeds, but in a short time, which is very cost-intensive. Based on the foregoing, in order to eliminate the risks associated with safety violation, to confirm the design speed and in order to reduce costs when applying new rolling stock, a full-scale virtual method has been proposed that provides the use of a computer simulation, in which the design speed specified in the technical documentation is set at the stage of rolling stock development, taking into account the operational variability of car running gear and the track state.

Impact of rail impedance intrinsic variability on railway system operation, EMC and safety

Running rails in electrified transportation systems are the interface element for several phenomena related to system performance, electromagnetic compatibility and safety: useful voltage at rolling stock, short circuit current, induced voltage, stray current, and track circuit operation. This work presents the physical and mathematical groundings of rail electrical parameters (dc and ac resistance, ac internal and external inductance) and experimental results available in the literature, discussing variability and reliability for each interface. The results consist thus of the identification of the relevant rails longitudinal electrical parameters, the presentation of a set of reliable experimental values, and the discussion of the best approach to manage their variability and uncertainty.

Distribution Correction Model of Urban Rail Return System Considering Rail Skin Effect

The problem of high rail potential is common in urban rail transit lines that use running rail to return train current. At present, the research of rail potential mainly adopts modeling analysis. However, the rail potential results of the traditional model are generally far less than the actual situation, and the distribution is not accurate enough. It is difficult to predict the rail overvoltage in actual operation by the traditional model. This article explains the reason for the low accuracy of the traditional model from the perspective of the rail skin effect and corrects the rail resistance parameters of the traditional model. A calculation method of rail skin effect equivalent resistance is proposed, and a distribution correction model is established to simulate the rail potential. Compared with the traditional model, the rail potential results of the correction model are obviously increased, and the value and distribution of rail potential are closer to the actual system. The accuracy of the traditional model is improved obviously after the correction of rail resistance parameters, and the problem of inaccurate analysis and prediction of OVPD by traditional models has been solved.

Research on Subhealth Diagnosis Method for Resistance of Urban Rail Transit Door System

The rail vehicle door system is one of the key components of rail vehicles. Its failure rate accounts for more than 30% of vehicle failures. By analyzing early warnings provided by subhealth data from the door system, the efficiency and reliability of their health maintenance can be effectively improved and stable operation of the door system can also be guaranteed. In this paper, early-stage resistance changes in the subhealth state of rail vehicle door systems are considered as the research object. Firstly, the distribution rules for the motor parameters are studied, and the time-domain and normal operating envelope features of the operating motor are extracted. Secondly, subhealth conditions with different resistances are simulated using a test rig, and the experimental data are applied to summarize the rules. According to the subhealth types and the distribution of features, diagnostic rules for subhealth are formulated. To check the possibility of fault diagnosis, a verification using running rail vehicle door system data is carried out in MATLAB. The results reveal that the misdiagnosis rate of resistance subhealth is 0% while the rate of missed diagnoses is 2%. Meanwhile, the diagnostic process based on the established rules is relatively efficient. This method is suitable for application for resistance subhealth diagnosis of urban rail vehicle door systems.

On the interference mechanism of stray current generated by DC tram on pipeline corrosion

The stray current from the DC-electrified traction system can affect the pipeline-to-soil potential and can cause corrosion on the buried pipeline, which will bring about economic losses and even threaten personal safety. Thus, it is necessary to study the stray current generated by the rail potential and its impacts on pipeline corrosion. For this purpose, an analysis approach, in which the theoretical method is used in combination with the finite element model and experimental analysis, is presented. The dynamic distribution equations of the rail potential and the stray current are deduced by using a mathematical model. A finite element model based on the theoretical equations is established to calculate the pipeline-to-soil potential under the interference of the stray current from the running rails. Finally, the obtained pipeline-to-soil potential is used as voltage interference to develop an electrochemical experiment and the variation laws of the electrochemical impedance spectroscopy of the pipeline metal are studied by using this experiment. The theoretical results show that the stray current is proportional to the rail potential. The pipeline-to-soil potential under the interference of different stray current can be expressed as a sine function according to the fitted results of the finite element analysis. And the coefficients of the function are determined by the relative position of the pipeline and the running rails. Meanwhile, the coefficients of the function (amplitude, frequency, and offset) have different influence on the EIS of the pipeline metal.

Analysis of dynamics of a scaled PRT (personal rapid transit) vehicle

This publication provides a discussion concerning research aimed to analyse running properties of PRT vehicles. A PRT vehicle is guideway vehicle equipped with rubber-tyred wheels, running on a flat subgrade guideway of special design. The guideway cross-section is similar to that of a C-shaped beam with two outer limiting edges. This specific design characteristic of the running system of PRT vehicles distinguishes them from typical rail vehicles, where the latter can move along the track by the action of a unit referred to as the centring mechanism, operating at the contact of profiled wheels with the running rail head. In a PRT vehicle, the typical railway centring mechanism has been removed and substituted with a system of outer and inner rollers, forming what is referred to as a passive switch system, responsible for carrying the vehicle along the guideway and within the boundaries delimited by its edges by the action of the rollers’ contact forces. Compared to railway infrastructure, this system is characterised by different dynamic properties, and it has not been sufficiently researched yet. The goal of this article is to analyse motion stability of a PRT vehicle with a passive switch system and having the following structural features: wheel sets with beams turning against the vehicle body and independently revolving wheels, non-turning rubber-tyred and non-profiled wheels rolling on a flat surface, and a set of outer and inner rollers performing the passive switch system’s functions. The paper describes a PRT vehicle simulation model. It has been assumed that the model’s design and parameters describe a scaled vehicle/guideway system whose physical model is actually set at a laboratory testing station on premises of the Warsaw University of Technology. The article provides results of simulation studies of motion stability pertaining to the following characteristics: radial positioning, yawing, sticking to the guideway edge, self-excited vibrations of wheel sets as well as free vibrations. It also discusses results of an analysis of sensitivity of the model’s parameters against selected control parameters (model’s design parameters) and assessment indicators which describe the intensity of the yaw type torsional vibrations of wheel sets. The article closes with a discussion on the potential to use the results of the tests conducted under the study on the scaled vehicles in question for purposes of vehicles of real-life dimensions.

A New Cooperative Anomaly Detection Method for Stacker Running Track of Automated Storage and Retrieval System in Industrial Environment

Considering the complexity and the criticality of the stacker equipment, in order to solve the problem that the stop accuracy of the stacker reduces or even fails to work due to abrasion of the running rail, this paper proposes a cooperative detection method based on Pulse Coupling Neural Network (PCNN) and wavelet transform theory to detect the abnormal points of the stacker running rail in industrial environment by analyzing the variation signals. First of all, considering the fact that the data is mixed up with noises because of the environment at the site and the possibility of the data acquisition equipment breaking down, a noise reduction method for the vibration signal data of stacker is constructed based on PCNN. Then, the basic theory of wavelet transform is introduced and then the rules of judging anomaly points on stackers’ running tracks are discussed based on wavelet transform. In addition, a cooperative detection method based on PCNN and wavelet transform theory is carried out based on the space-time distribution feature of the vibration of the stacker orbits in the industrial environment. Then the rationality of the proposed algorithm is verified by simulation through data provided by State Grid Measuring Center of China. This paper constructs a model of the abnormal point detection of the stackers in an industrial environment. The experimental simulation and example simulation show that the cooperative detection method based on PCNN and wavelet transform theory can effectively detect and locate the anomaly points of the stacker running tracks. The expansibility in engineering applications is promising. Lastly, some conclusions are discussed.

Mitigating Train Derailments Due to Sharp Curve and Overspeed

Each year around the world there are still several cases of train derailments on the curved tracks due to overspeed, leading to big casualties and costs to the rail industries. With the ongoing increase on the speed, the possibility of train derailment increases, especially on the sharp curved tracks. Guard rails are usually placed parallel to regular running rails along areas of restrictive clearance, such as a bridge, tunnel, or sharp curved track. They have the effect of keeping the wheels of rolling stock in alignment in case of derailment. The investigation on the guide rail which is used to mitigate the train derailment due to a curved track and overspeed is carried out through the simulations. The simulation results show that installing guard rails can largely reduce the train derailment potential caused by a sharp curve and overspeed. The clearance between the low rail and the guard rail (namely, the flangeway width) is critical for the effectiveness of guard rail. The optimal position of guide rail – the height over the top of low railhead and lateral distance between guide rail and low rail would be determined through the simulations.

Maximum Safety Regenerative Power Tracking for DC Traction Power Systems

Direct current (DC) traction power systems are widely used in metro transport systems, with running rails usually being used as return conductors. When traction current flows through the running rails, a potential voltage known as “rail potential” is generated between the rails and ground. Currently, abnormal rises of rail potential exist in many railway lines during the operation of railway systems. Excessively high rail potentials pose a threat to human life and to devices connected to the rails. In this paper, the effect of regenerative power distribution on rail potential is analyzed. Maximum safety regenerative power tracking is proposed for the control of maximum absolute rail potential and energy consumption during the operation of DC traction power systems. The dwell time of multiple trains at each station and the trigger voltage of the regenerative energy absorbing device (READ) are optimized based on an improved particle swarm optimization (PSO) algorithm to manage the distribution of regenerative power. In this way, the maximum absolute rail potential and energy consumption of DC traction power systems can be reduced. The operation data of Guangzhou Metro Line 2 are used in the simulations, and the results show that the scheme can reduce the maximum absolute rail potential and energy consumption effectively and guarantee the safety in energy saving of DC traction power systems.

System for measurement of interaction forces between wheel and rail for railway vehicles

Determination of the interaction forces between wheel and rail of railway vehicles is essential for assessment of the vehicle dynamic characteristics from point of view of running safety and rail loading as well as for approval the vehicle and alignment them to the Technical Specification for Interoperability. The direct measurement of transverse and vertical interaction forces using the existing full-disk wheel is practical impossible due to the impossibility of separating the two types of forces. To avoid this impediment it was realized a measuring wheelset fitted with 12 spokes achieved as force transducers for measurement of the vertical forces and 12 spokes achieved as force transducers for measurement of the transverse forces. The measuring wheelset was calibrated as a force transducer and was used to determine the wheel and rail interaction forces for LE-MA 6000kW electric locomotive made by Softronic Craiova. The article presents the measuring wheelset, the calibration principle and the calibration characteristics as well as some time history of the main parameters which characterize the running safety and rail loading, determined in the on-track tests.