Overhead Contact Line Research Articles

Saving energy resources during operation of rolling stock of underground electrified transport

Purpose. To analyze the energy saving reserves under the conditions of implementation and integration of the system in order to find rational driving modes in the general system of managing underground electrified transport. Methodology. The work presents the method for processing data arrays obtained experimentally with the help of a measuring system and theoretically with the use of the “Rational Trajectory” software. Findings. Experimental studies were carried out using a testing system created on the basis of a refurbished train with energy recovery system. Theoretical studies were carried out using the “Rational Trajectory” software, which is based on the principle of solving a multi-criteria problem by the method of the main criterion. The minimum amount of electricity consumption from the overhead contact line was chosen as the main criterion. The software was developed in the LabVIEW graphical programming environment in order to determine the rational modes of driving rolling stock and energy indicators in a given area of its operation. The amount of electricity consumed for traction and the amount of electricity generated by the train during regenerative braking were determined based on the results of experimental and theoretical studies, respectively, under typical and rational modes of driving the train for given identical operating conditions. Originality. Further research on the analysis of energy saving reserves on the rolling stock of underground electrified transport was achieved due to the introduction of a system for finding a rational driving mode. Practical value. It has been established that the implementation and incorporation of the “Rational Trajectory” software into the train control system will save up to 14.7 % of the amount of electricity consumed for traction, compared to typical modes operation on a given track section.

Modelling and simulation of double-pantograph catenary system of Taiwan railway

Abstract In view of the insufficient transportation capacity of Taiwan Railways in populated urban areas and intercity railways, increasing the maximum operating speed can be a solution for the problem. However, it is unknown whether the overhead contact line (OCL) system of the Taiwan Railways can tolerate such speed changes. For the unique railway system used in Taiwan, the literature does not present research on the dynamic interaction behaviour for the typical EMU trains with two pantographs, which are widely used in Taiwan railway system. Further, in response to the government policy to localize the supply chain of railway components, this research aims to establish a reliable simulation model so that domestic manufacturers may use this model for the design and development of the pantograph-catenary system. In this study, the catenary system model is established based on theoretic principles, specifications and parameters are adapted from data used by Taiwan Railway Co. The pantograph model was constructed as multi-body model, with parameters taken from the pantograph equipped on the TEMU2000 tilting train. This model is used to analyse catenary system to investigate the potential loss of contact between the double pantographs and the contact wire with increased train speed. The loss of contact and other phenomena will be analysed to explore possible solutions or optimization strategies for catenary system design.

Railway Infrastructure Management: Selection of Overhead Contact Line Ampacity Considering Operational and Design Factors

This paper presents a novel approach to determining the ampacity of DC and AC railway overhead contact lines, considering both operational and design factors. The ampacity of contact lines is influenced by several design parameters, including materials, cross section and the number of catenary and contact wires, etc. Additionally, the permissible long-term and short-term current values, which correspond to the permissible temperatures defined by EN 50119:2020, are affected by operational factors such as ambient temperature, solar radiation, heat exchange conditions, wind speed, wear of contact wires. Existing methods for determining the ampacity of overhead contact lines often fail to account adequately for these critical factors and lack the necessary procedures to calculate the 30 min ampacity required by EN 50119:2020. In response, the method proposed in this study adapts the procedures of IEEE 738-2012 to the specific needs of railway contact lines, taking into account the effect of contact wire wear on current distribution and overall ampacity. The proposed method offers a more realistic and practical approach to determining the ampacity of contact lines, thereby enhancing the reliability and efficiency of the traction power supply infrastructure. This method could be useful for railway infrastructure managers to ensure the safe and efficient operation under varying environmental and operational conditions.

Availability of an Overhead Contact Line System for the Electrification of Road Freight Transport

Availability of an Overhead Contact Line System for the Electrification of Road Freight Transport

Impact of an eHighway on the directly emitted greenhouse gases by road freight transport

German legislation sets forth that anthropogenic greenhouse gases must be net-zero from 2045 onward (KSG, 2019). In contrast, road freight transport is projected to grow significantly (BMVBS, 2008; BMVI, 2021). If sustainable solutions for road freight transport are not implemented swiftly, Germany will not be able to meet its climate protection targets. This study analyzes the potential of the eHighway system—an overhead contact line-based electrification of trucks—to reduce the road freight transport's carbon footprint. Based on more than three years of field test operation with over 500,000 real-world driven kilometers, we estimate the saving potential of directly emitted greenhouse gases from five pilot overhead contact line trucks that use the eHighway system (O-trucks). We conclude that with only a five percent electrified stretch of a trip, 14–17% of direct greenhouse gas emissions are saved compared to a conventional truck. We develop a scaling and comparison calculator for the estimation of directly emitted greenhouse gases of O-trucks. We argue that with an electricity mix based upon renewable energies and an appropriately extended eHighway network, road freight transport is capable of offering transport with net-zero greenhouse gas emissions. Based on a unique data set, we provide a benchmark for all further research in evaluating eHighway technology and for comparing it to alternative drive technologies.

Remote estimation of cable tension using catenary theory and point clouds obtained by terrestrial laser scanning

This study addressed the structural health monitoring of civil engineering cable structures, in which single cable tension is the key parameter influencing safe and intended behaviour. Traditional methods for monitoring the tension force in a cable are labour-intensive and require direct interaction with the cable. In contrast, the proposed approach provides a remote and rapid assessment of the tension force in the cables of engineering structures using only the shape of the cable. First, a terrestrial laser scanner was used to acquire a point cloud of the cable geometry from a distance. Catenary theory was subsequently applied to the point cloud data to calculate the theoretical tensile force in the observed cable. When the results were compared with those obtained through conventional direct measurements using a dynamometer, the differences were negligible. The proposed approach was subsequently demonstrated on the actual in-service overhead contact lines of a tram system. The results indicated that the precision of the proposed approach is highly dependent on the accuracy of the data describing the physical properties of the cable (cable linear mass). Thus, the proposed approach was proven to be precise, reliable, and rapid, and directions for future research were discussed accordingly.

Analysis of Technical and Operational Requirements of Alternative Drive Systems by Transport Companies: The Case of the Overhead Contact Line Truck

A change to zero-emission drive systems in road freight transport is required to achieve climate protection targets. Therefore, alternative drive systems for road freight transport are being tested in field trials in Germany. One such technology is the eHighway system. The eHighway system combines an overhead contact line hybrid truck (OH truck) and an overhead contact line infrastructure. The objective of this study was to evaluate technical and operational success factors and barriers influencing the adoption of the eHighway system by freight transport companies. We evaluated expert interviews, written surveys, and vehicle data. We found that transport companies had no major restrictions concerning the technical equipment of the OH trucks. Furthermore, we found no operational restrictions in the use of OH trucks while the OH trucks can be integrated into different transport operations.

Data-Driven Time Dependent Reliability Prediction Approach for Overhead Contact Lines Subjected to Imperfect Maintenance, Common Cause Failure and Lightning Strike

Data-Driven Time Dependent Reliability Prediction Approach for Overhead Contact Lines Subjected to Imperfect Maintenance, Common Cause Failure and Lightning Strike

Active Displacement Control of Pantograph-catenary System for a Half-body Railway Model

The pantograph is an essential component that provides electrical contact between the overhead wires and the electric train. The quality of the current collection in high-speed trains is directly influenced by the mechanical interaction between the pantograph collector head and the overhead contact line. To overcome these challenges and improve pantograph performance, researchers and engineers have explored innovative solutions, including the introduction of active control mechanisms. Excitation by the vehicle is one of the normal disturbances in the dynamic interaction of the pantograph and the overhead line. The vertical effects of vehicle-track vibrations on the interaction between the pantograph and the overhead contact line have not yet been adequately researched. To fill this research gap, this study establishes models for both the pantograph-catenary interaction and the vehicle-track system. In this study, the performance of the modified Skyhook-Proportional-Integral-Derivative (PID) controller was investigated for a half-body of a railway pantograph-catenary system. Track irregularities such as step, sine, and random were applied to perturb the suspension system. The performance of both passive and active systems was investigated by considering the track irregularities as a basis. The root mean square analysis (RMS) found that active displacement control of pantograph-catenary systems for a half-body railway model equipped with modified Skyhook-PID controllers performed better than the passive systems. In summary, the future experimental approach for active half-body railway model could incorporate this simple modification of the Skyhook-PID controller.

A Real-Time Siamese Network Based on Knowledge Distillation for Insulator Defect Detection of Overhead Contact Lines

A Real-Time Siamese Network Based on Knowledge Distillation for Insulator Defect Detection of Overhead Contact Lines

Problems of simulation of the pantographcatenary contact line interaction in terms of interoperability

The paper presents the application of the pantograph-overhead contact line interaction simulation, which is carried out to assess the fulfillment of the essential interoperability requirements for the interoperability component, which is the overhead contact line. According to the paper's authors, carrying out model validation according to the EN 50318:2002 standard indicated in the technical specification for interoperability does not exhaust the question of the correctness of the method used. This fact is also confirmed in the literature discussed in the paper. To substantiate the above thesis, a numerical simulation was carried out in MATLAB/Simulink using a two-mass model of the pantograph and overhead contact line. As a result of the sensitivity analysis of the influence of the input data on the simulation results, conclusions were formulated to confirm the thesis in question.

Robust deep Gaussian process-based trustworthy fog-haze-caused pollution flashover prediction approach for overhead contact lines

Due to completely open-air operation, fog-haze has become the main cause of contamination on the insulator surface of overhead contact lines (OCLs), further leading to pollution flashover and a series of serious risk consequences. To perceive the fog-haze-caused pollution flashover (FHPF) risk of OCL insulator, a robust deep Gaussian process (DGP)-based uncertainty-aware trustworthy prediction approach is proposed, incorporating epistemic and aleatoric uncertainties. In particular, aiming at the imbalanced dataset with limited fault samples, the prediction of FHPF risk is cast as a classification problem, and solved by DGP using stochastic gradient Hamiltonian Monte Carlo (SGHMC) inference. The key parameters are identified investigating the influences of fog-haze on insulator surface contamination. Furthermore, the SGHMC sampling-based inference is utilized to efficiently capture the intractable posterior distribution, dealing with uncertainty and enhancing the flexibility of the prediction approach. Finally, extensive experiments on high-speed railway line validate the effectiveness and superior of the proposed approach, compared to other advanced predictive classification methods. In addition, it cannot only capture the prediction uncertainty over a limited number of fault samples, but also achieve favorable prediction performance under unseen noisy environments, ultimately ensuring robust and trustworthy FHPF risk predictions for OCLs.

Uncertainty-aware trustworthy weather-driven failure risk predictor for overhead contact lines

Overhead contact lines (OCLs) are electric transmission lines that power railways, which are constantly threatened by external weather and environmental factors due to their outdoor location. Hence, for the long-term functioning of railway lines, a weather-driven risk predictor is an essential tool. Current prediction methods mainly adopt a single-point estimation system with fixed weights of neural networks and therefore cannot propagate the uncertainties within the data and model, resulting in unreliable predictions. To enhance safety-risk prevention capabilities, this paper proposes an uncertainty-aware trustworthy weather-driven failure-risk approach for OCLs, in a probabilistic deep multitask learning framework. Firstly, a deep Gaussian process is employed as the backbone model to deal with imbalanced weather-related failure datasets with limited fault samples. Moreover, a multi-task learning framework is embedded to simultaneously predict the multiple weather-driven failure risks under lightning, wind and haze. Finally, the predictive uncertainty is decomposed into epistemic and aleatory uncertainties, where epistemic and aleatory uncertainties account for the uncertainty within the model and data, respectively. Extensive experiments on actual OCLs are carried out to demonstrate the effectiveness of the proposed approach, which can effectively capture the predictive uncertainty and provide trustworthy predictive decisions of mitigating operational risk for railway operators.

A Non-Intrusive Monitoring System on Train Pantographs for the Maintenance of Overhead Contact Lines.

The condition monitoring of an overhead contact line (OCL) is investigated by developing an innovative monitoring system for a pantograph on an electrical multiple unit of a regional line. Kinematic and dynamic modelling of the pantograph is conducted to support the designed monitoring system. The modelling is proved through rigorous test-rig experiments, while the proposed methodology is then validated through extensive field tests. The field tests serve a dual purpose: First, to validate the monitoring system using benchmark measurements of the tCat® trolley, and second, to assess the reproducibility of measurements in a realistic case. This paper presents the OCL monitoring system developed in the framework of the H2020 project SIA. The accuracy of our results is not far from that of other commercial systems, with just 12 mm of absolute error in the height measurement. Therefore, they provide reliable information about trends in various key performance indicators (KPIs) that facilitates the early detection of failures and the diagnosis of anomalies. The results highlight the importance of model calibration and validation in enabling novel health monitoring capabilities for the pantograph. By continuously monitoring the parameters and tracking their degradation trends, our approach allows for optimized scheduling of maintenance tasks for the OCL.

Study on Aerodynamic Instability and Galloping Response of Rail Overhead Contact Line Based on Wind Tunnel Tests

The overhead contact line is a tensioned cable structure erected along the railroad to power the electric train. Under the wind load, the galloping of OCL caused by aerodynamic instability may form a large amplitude, which is a big potential threat to the normal operation of the electric railway. In this paper, a wind tunnel test is performed to investigate the aerodynamic coefficients of the contact line with two levels of wear. The aerodynamic instability of the contact line can be observed on a worn contact wire at around an 8° wind angle of attack. Employing a nonlinear finite element model of the OCL, the galloping is reproduced and analysed via several numerical simulations. The effect of the wear level and angle of attack on the galloping response is analysed. The galloping amplitude of the contact line spikes at the angle of attack of 8° and 9° at 20% and 30% wear levels, respectively. Then damping dropper is included in the model, and its effect on the suppression of the OCL galloping is quantified. The results indicate that a damping dropper of 100 Ns/m is recommended to be mounted on the railway OCL to reduce the detriment of galloping under a strong wind field.

A study on the optimal spatial damping distribution in railway pantograph-catenary interaction

Railway overhead contact lines are very low-damped structures with a high modal density in the low-frequency region. This has a significant impact on the interaction with the pantograph, especially in the high-speed case and in multiple pantographs operations. This paper studies the optimal spatial damping distribution in overhead contact lines obtained by introducing localised damping connections, resulting in a non-proportional damping distribution. To this end, the simulation software Cateway is presented and adopted in conjunction with evolutionary multi-objective optimisers to seek for the most efficient spatial damping distribution. The study is conducted on a high-speed reference model considering two different train speeds. The final goal of this optimisation is to obtain useful hints about the most and least sensitive regions to damping modifications. A dedicated study on the locus of the poles of the system is also proposed to corroborate the findings of the analysis. Results show that significant improvements on the current collection quality can be achieved by carefully designing the spatial damping distribution, especially for the rear (trailing) pantograph. On the other hand, wrong design choices can lead to a degradation of the contact forces.

A data-driven integrated framework for predictive probabilistic risk analytics of overhead contact lines based on dynamic Bayesian network

Due to completely working under open-air conditions without backup equipment, the overhead contact lines (OCLs) are suffering from external extreme weather conditions, except for the long-term dynamic vibrations of catenary-pantograph system. These risk factors are prone to cause failures of OCL components and power outages, which may further result in transportation interruptions, enormous economic losses, serious social impacts, and even catastrophic safety accidents. To comprehensively investigate the associated risks in OCLs, a data-driven integrated predictive probabilistic risk analytics framework based on dynamic Bayesian network is proposed to identify the significant risk factors and analyse the time-dependant failure patterns in dynamic risk propagation network of OCLs. After exploiting the weather-driven analytics for failure probability prediction, an integrated failure probability modelling for OCL components is developed, simultaneously incorporating internal, and weather-driven hazard factors of OCLs. A predictive risk metric is suggested based on the newly established risk propagation network of OCLs, which can account for weather hazards, system failures, financial costs, and social trust losses, in response to external weather conditions over time. Numerical studies conducted on the actual OCLs demonstrate that the proposed framework can dynamically model and evaluate risks of failure patterns that expose to OCLs.

A Multilayer Bayesian Network Approach-Based Predictive Probabilistic Risk Assessment for Overhead Contact Lines Under External Weather Conditions

Due to being completely exposed outdoors without backup, overhead contact lines (OCLs) are more vulnerable to external weather conditions. To perceive the weather-related failure risk and evaluate the associated potential risks, a multilayer Bayesian network (MLBN) approach is proposed for predictive probabilistic risk assessment for OCLs. More specifically, the weather-driven failure probabilities of OCLs are predicted using a first-layer Bayesian network (BN), including lightning strikes, windstorms, and fog-haze. Then, the weather-driven failure patterns of OCLs are investigated and captured, and furthermore, the second-layer BN is embedded to evaluate the risk propagation. Furthermore, the third-layer BN is implemented to calculate and quantify weather-driven risk consequences from perspectives of economic loss and social trust loss constrained by power outage time and train timetable. The three-layer BN models are built by connecting the nodes with causal relationships, avoiding complicated structure learning. The experiments on the actual OCL failure records and weather data demonstrate that the proposed MLBN approach can identify weather-involved risk activities and comprehensively analyze the weather-driven cumulative risks of OCLs from spatiotemporal perspectives. In addition, it is capable of giving reasonable guiding information for mitigating the operational risks of OCLs against external weather conditions.

Data-driven lightning-related failure risk prediction of overhead contact lines based on Bayesian network with spatiotemporal fragility model

Data-driven lightning-related failure risk prediction of overhead contact lines based on Bayesian network with spatiotemporal fragility model

Damage Caused by Material Defects of Carbon Composites Used on Various Types of Railway Pantographs.

Mainstream materials of the railway pantograph strips are carbon composites. They are subject to wear during use, as well as various types of damage. It is important that their operation time is as long as possible and that they are not damaged, as it may damage the remaining elements of the pantograph and the overhead contact line. As part of the article, three types of pantographs were tested: AKP-4E, 5ZL, and 150 DSA. They had carbon sliding strips made of MY7A2 material. By testing the same material on different types of current collectors, it was possible to check what impact the wear and damage of the sliding strips has on (among others) the method of their installation, i.e., whether the damage to the strips depends on the type of current collector and what is the participation of damage caused by material defects. As a result of the research, it was found that the type of pantograph on which it is used has an undoubted influence on the damage characteristics of the carbon sliding strips, whereas the damage caused by material defects can be classified as a more general group-the group of damage of a sliding strip, which also includes overburning of a carbon sliding strip.