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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <language>en-us</language>
    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
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      <link>https://trid.trb.org/</link>
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    <item>
      <title>Dynamic icing and flashover characteristics of roof insulators under airflow conditions</title>
      <link>https://trid.trb.org/View/2681692</link>
      <description><![CDATA[Roof insulators in railways operate under complex airflow conditions, where combined pollution and icing can significantly degrade insulation performance. To investigate the dynamic icing behavior and flashover characteristics of roof insulators under such conditions, icing simulations in a moist airflow environment and flashover experiments were conducted using an aerodynamic icing platform. The results indicate that, under airflow conditions, slow freezing ice accretion with ice ridge formation occurs in the temperature range of −4 °C to −7 °C, corresponding to wet growth icing, whereas rapid freezing ice accretion without ice ridges predominates at temperatures below −10 °C, characteristic of dry growth icing. Wet growth icing shows much higher sensitivity to airflow velocity than dry growth icing. With increasing equivalent salt deposit density (ESDD), polluted insulators under −4 °C wet growth icing exhibit distinct flashover behavior compared with uniced polluted insulators and those under −13 °C dry growth icing, with flashover voltages concentrated in a low range of 40–50 kV. To account for this behavior, a modified Obenaus flashover model is established, highlighting the strong dependence of flashover voltage on the flashover path. A side windward ice ridge looseness factor B is introduced to improve voltage prediction for typical wet growth polluted insulators. The results provide practical guidance and modeling support for the safe operation and structural optimization of roof insulators in severe environments.]]></description>
      <pubDate>Thu, 25 Jun 2026 09:40:59 GMT</pubDate>
      <guid>https://trid.trb.org/View/2681692</guid>
    </item>
    <item>
      <title>Visual Measurement and Uncertainty Prediction of Insulator Thickness in Insulated Rail Joints</title>
      <link>https://trid.trb.org/View/2672802</link>
      <description><![CDATA[Railway tracks are critical to social infrastructure, and their maintenance is essential for operational safety. Glued Insulated Rail Joints (GIRJs) are vital for railway signal control, where the insulator’s thickness helps prevent signal failures. This paper addresses detecting anomalies in GIRJ insulator thickness using images captured by devices on operational trains. Due to various factors, the insulator is not always clearly visible, and standard computer vision methods often struggle. In severe cases, judgments cannot be made from the image alone, requiring the system to return “unable to determine.” If these cases are rare, they can be manually inspected, still lowering overall inspection costs. We tackle this by framing the task as a one-dimensional regression problem, using convolutional neural networks (CNNs) to predict the boundary between the insulator and rail, while also estimating prediction uncertainty. Experiments with real-world data show that the model is accurate enough for practical use, even with challenging images. Additionally, we propose a robust method for detecting GIRJs in long-range railway images. This system is now operational in railway inspections.]]></description>
      <pubDate>Wed, 24 Jun 2026 11:31:26 GMT</pubDate>
      <guid>https://trid.trb.org/View/2672802</guid>
    </item>
    <item>
      <title>Leakage Current-Based Contamination Level Evaluation of On-Board Insulators Using 2-D Fused GAF Images and DSC-CBAM-ResNet Network</title>
      <link>https://trid.trb.org/View/2659168</link>
      <description><![CDATA[On-board insulators are key components of the electric multiple units (EMUs) power system, and accurate evaluation of their contamination level (CL) is of great significance in preventing contamination flashover accidents and ensuring the safe operation of equipment. Current methods rely on manual experience, which is inefficient and prone to errors. This article proposes a novel method for evaluating the CL of on-board insulators in EMUs, aimed at improving detection efficiency and adaptability to complex field environments. The proposed approach utilizes the Gramian angular field–visual saliency map–weighted least square optimization (GAF-VSM-WLSO) framework combined with a depthwise separable convolution–convolutional block attention module-ResNet18 (DSC-CBAM-ResNet18) network. Initially, the leakage current (LC) signal is transformed into a 2-D color fusion GAF image through the above-mentioned composite framework, which can capture both the global structure and local details. A composite model is then constructed, enhancing feature extraction by introducing the DSC module to reduce computational complexity and the CBAM attention mechanism to highlight key features. The model is optimized with the focal loss (FL) function to improve classification accuracy for difficult samples. Ablation study and comparison experiments demonstrate that the fusion image outperforms normal 2-D images in feature representation. The proposed model achieves 98.67% recognition accuracy, with a  $0.9867~F1$  score and a 0.9968 multiclass AUC value, outperforming other models and confirming its superior performance and robustness in CL evaluation of insulators.]]></description>
      <pubDate>Thu, 16 Apr 2026 13:54:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/2659168</guid>
    </item>
    <item>
      <title>Optimization of Intense Electric Field Electrodes for Pantograph Support Insulators of CRH2 High-Speed Train Under Overvoltage Conditions</title>
      <link>https://trid.trb.org/View/2512007</link>
      <description><![CDATA[The bolt above the first umbrella skirt of the pantograph postinsulator of the high-speed train will distort the electric field in its vicinity, the overvoltage during the high-speed train passing from one electric section to another may cause arcs, and the partial arcs will burn the umbrella skirt or even induce flashover fault, so it is necessary to install a grading ring with a rational structure to reduce the local electric field intensity and consider the change of the streamline distribution near the first umbrella skirt after installing a grading ring; an elliptic grading ring (EGR) and rod-shaped bolt shielding cover (SC) were designed in this article. Then, the structural parameters of the grading rings were optimized by using the orthogonal test method, and the tests were carried out to obtain the change of corona inception voltage, 50% lightning impulse voltage, and power frequency dry flashover voltage. The results show that after the simultaneous installation of EGR and SC, meanwhile the maximum electric field strength at the root of the first umbrella skirt decreased by 88.7%, the flashover voltage of the insulator model complies with the relevant specifications after optimizations. The corona discharge inception ac voltage value at the bolt end for the original model is 60 kV, no obvious discharge faculae can be seen around the ring surface when the voltage is up to 110 kV. The results can provide a reference for the structure selection and parameter optimization of the grading devices in a high-speed airflow environment.]]></description>
      <pubDate>Fri, 23 May 2025 15:34:43 GMT</pubDate>
      <guid>https://trid.trb.org/View/2512007</guid>
    </item>
    <item>
      <title>A Cooperative Optimization Method of Electric Field-Flow Field for Roof Insulators of High-Speed Trains</title>
      <link>https://trid.trb.org/View/2511701</link>
      <description><![CDATA[Aerodynamic drag generated during the high-speed train operation not only lowers operating efficiency and increases power consumption but also restricts the speed for further improvement. As the existence of roof external insulation equipment, the aerodynamic drag on the roof increases and the optimization of drag reduction for it is an essential development trend. In this article, a simulation model for the external insulation equipment is first established and validated. Also, a cooperative optimization method of electric field-flow field of roof insulator based on micro-macro bionic structure is proposed. Second, the datasets, including eight input parameters and two output parameters, are collected. Four surrogate models are constructed and compared to determine the preferable model. Then, the optimal structural parameters are obtained using the multiobjective particle swarm optimization (MOPSO) algorithm. The flow field and the electric field of roof insulator before and after optimization are analyzed. Finally, the 3-D printed insulators are employed to verify its insulation performance. The results show that the optimized roof insulator can achieve 21.33% drag reduction. The average electric field strength decreases by 8.19%, and the flashover voltage is significantly improved. The cooperative improvement of aerodynamic drag reduction-insulation performance of the roof external insulation equipment is realized.]]></description>
      <pubDate>Mon, 14 Apr 2025 09:35:23 GMT</pubDate>
      <guid>https://trid.trb.org/View/2511701</guid>
    </item>
    <item>
      <title>Partial Discharge Free Insulation Design for Slotless Machines With Magnet Wire Conductors and Winding Encapsulation for Aerospace Applications</title>
      <link>https://trid.trb.org/View/2511352</link>
      <description><![CDATA[Slotless motor is a suitable propulsion component candidate for high-speed aerospace applications due to their lightweight, low iron losses, and superior efficiency at high fundamental operating frequencies. The winding insulation design of the slotless machines requires special attention to ensure partial discharge (PD)-free operation due to the lower pressure levels at higher altitudes in aerospace applications. Finite-element analysis (FEA)-based simulations revealed that the maximum electric field strength is impacted by the separation distance between the random wound magnet wire conductors, thereby increasing the risk for PD in a low-pressure environment. Encapsulating the winding with high-strength dielectric material ensures reliable insulation, enhances manufacturing robustness, and improves thermal conductivity. The effect of potting thickness, defects in the potting, and relative permittivity of insulation have been analyzed using finite-element (FE) methods. The PD inception at reduced pressures was experimentally analyzed and corroborated with FEA using several samples of encapsulated coils.]]></description>
      <pubDate>Tue, 25 Mar 2025 16:57:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/2511352</guid>
    </item>
    <item>
      <title>Detecting and Mitigating Low-Level DC Leakage and Fault Currents In Transit Systems



</title>
      <link>https://trid.trb.org/View/2487299</link>
      <description><![CDATA[Low-level electrical fault currents are phenomena found in direct current (DC) traction systems used in public transit systems and electrified rail systems worldwide. These low-level currents are typically caused by small and sporadic failures of insulation within the electrification system, which often make them difficult to locate, measure, and control. The apparent effects of these faults can go unnoticed for long periods of time as a result of their slow and progressive nature; however, if these faults are left undetected, evidence exists to show that extensive damage to infrastructure of transit systems and infrastructure of adjacent private/public utilities may result. Recently, a transit system suffered damage to its electrification system because of low-level faults in the central core area. The failure resulted in damage valued at more than a million dollars that impacted rush hour revenue service at the time of occurrence. The failure further necessitated service reductions for several days in the central core transit system area while emergency repairs were performed. Similar problems have occurred at other transit agencies.
 
Low-level DC leakage and fault currents may also create safety hazards to transit employees, patrons, and the general public as contact to any metallic structure (such as fences, light poles, and handrails) is potentially lethal because structures may become energized to dangerous voltages. At present, awareness of such hazards is dependent on acute conditions observed (e.g., boom, flame, smoke, steaming or glowing poles, steaming manholes, smoking insulators; train doors that do not open) or felt (e.g., sluggish train operation; shock or tingle on contact; hot water in cable hole), as well as chronic conditions observed (e.g., rail deterioration, rail web entirely destroyed, burnt surge arresters).
 
Currently, there are no known technologies available to easily detect low-level DC leakage and fault currents. To detect low-level DC leakage and fault currents (at the agency level), it is necessary to conduct extensive field research, which is costly, labor intensive, and difficult to accomplish, particularly in areas remote from traction power substations. With current operating budget restrictions prevalent throughout the industry, this type of testing is not feasible. Research is needed to identify possible workable solutions; develop prototypes for detection and monitoring systems; and, produce a guide to mitigating low-level DC leakage and fault currents.
 
The objectives of this research are to develop (a) one or more prototype methods, tools, or techniques for detecting/monitoring low-level DC leakage and fault currents (i.e., magnitude of current and location of fault) in electrified transit systems and (b) a guide to detecting and mitigating low-level DC leakage and fault currents in transit systems. Electrical faults of interest include, but are not limited to, those originating from subsurface conductors as well as third rail and overhead contact systems.
 
]]></description>
      <pubDate>Tue, 07 Jan 2025 18:09:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2487299</guid>
    </item>
    <item>
      <title>Evaluation of Impact of Volcanic Ash on Railway Electric and Signal Equipment and Proposal for Utilizing Information on Ash Fall</title>
      <link>https://trid.trb.org/View/2458865</link>
      <description><![CDATA[Volcanic ash fall can seriously affect railway operations by causing problems such as track circuit shunting malfunctions and decrease in insulation performance of insulators. In this study, the authors experimentally investigated volcanic ash conditions that cause these problems. Results allowed them to clarify that 0.05 mm thick volcanic ash causes shunting malfunction, and that 1.2 mm thick volcanic ash containing saline water causes insulator flashover. Based on these results, the authors propose preventive actions which railway companies can implement to mitigate the effects of ash fall, using public information on eruptions.]]></description>
      <pubDate>Tue, 03 Dec 2024 17:10:41 GMT</pubDate>
      <guid>https://trid.trb.org/View/2458865</guid>
    </item>
    <item>
      <title>Insulation Reinforcement for Cable Connector of CRH2 Electric Multiple Unit Under Standard Lightning Impulse Voltage</title>
      <link>https://trid.trb.org/View/2402248</link>
      <description><![CDATA[In order to improve the insulation capacity of cable connector (Cc) in the high voltage equipment box (Hveb), this article proposes an optimization scheme that does not change the size of the Hveb and the structure of Cc fittings. In this article, the change in the impulse voltage withstand value of Cc after installing insulating sheath was verified by the lightning impulse flashover test. Based on the finite-element software and the structure of Cc fittings, a special shaped shielding ring (Sr) was designed to adjust the partial area where the electric field intensity are concentrated. Besides, the optimal parameters of the Sr under different working conditions were determined by the orthogonal design. Finally, utilizing ultraviolet (UV) imaging technology and image processing method, the discharge intensity of Cc fittings were characterized. The results demonstrate that with the combination of insulation measures, the impulse voltage withstand value of Cc can be increased from 155 to 235 kV. The maximum electric field strength on the surface of bolts and metal electrode can be reduced by 57.8% and 72%; UV discharge facular area had an exponential relationship with the applied voltage, the initial discharge voltage of Cc can increase by 243% after installing the Sr.]]></description>
      <pubDate>Wed, 18 Sep 2024 09:41:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/2402248</guid>
    </item>
    <item>
      <title>Research on Transient Over-Voltages of High-Speed Train Passing Articulated Split-Section Insulator</title>
      <link>https://trid.trb.org/View/2402247</link>
      <description><![CDATA[The electromagnetic transient processes generated as a high-speed train (HST) passes the articulated split-section insulator cause over-voltages on the train roof and train body (TB), and thereby, an adverse effect is exerted on the electronic equipment. By this view, this article focuses on identifying the root causes and influencing factors pertinent to over-voltages. To begin with, the state-space analysis method is adopted to examine the probability and characteristics of arcing. Subsequently, the integrated vehicle-grid models associated with the split-section arcing are established to precisely simulate the over-voltage phenomenon in the independent transient processes of entering and leaving the insulator. The obtained results indicate that the hazardous over-voltages can be easily produced, and the behaviors of surges on the TB are very similar to that in the processes of rising and dropping pantograph. The influences of different variables, including the feeder phase, vehicle speed, lifting height, TB grounding pattern, and other HST’s simultaneous arcing impacts, are further revealed to discuss possible over-voltage suppression measures.]]></description>
      <pubDate>Wed, 18 Sep 2024 09:41:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/2402247</guid>
    </item>
    <item>
      <title>E-Field Simulation and Voltage Withstand Test Analysis of Solid Insulators for AC GIS Used in High-Speed Railway Traction Substation</title>
      <link>https://trid.trb.org/View/1975745</link>
      <description><![CDATA[The solid insulators are widely used in alternating current gas-insulated switchgear (GIS) equipment in high-speed railway traction substation. They have both mechanical support and electrical insulation functions. AC withstand voltage test is required before they are put into operation. In this paper, the series resonant circuit is theoretically analyzed, and the transient voltage change process of GIS solid insulators during sudden flashover is simulated and analyzed in the MATLAB/Simulink computing environment. The 3D electric field simulation of basin insulators and typical solid insulators with insulation support is carried out by using ANSYS electric field simulation platform. The withstand voltage test of the real interval of GIS is carried out to obtain the opening of circuit breaker. The relationship curves between Q, I and applied voltage U of solid insulator under two operating conditions are obtained. The results show that after flashover of solid insulators in series resonant circuit, the arc will be extinguished immediately after high voltage drop, and the recovery voltage will be established for a long time. The typical electric field distribution of solid insulators has concentrated area of local electric field, and flashover in field withstand voltage test starts in high field strength area. The research results of this paper provide some theoretical support for the field voltage withstand test of solid insulators used in AC GIS with series resonant circuit.]]></description>
      <pubDate>Tue, 06 Aug 2024 09:03:14 GMT</pubDate>
      <guid>https://trid.trb.org/View/1975745</guid>
    </item>
    <item>
      <title>Defects Detection of Onboard Cable Termination in EMUs Using Partial Discharge Measurement and SDP-DL Framework</title>
      <link>https://trid.trb.org/View/2201186</link>
      <description><![CDATA[Termination is the most important part of onboard cable, which plays a vital role in ensuring the continuous and reliable power supply to electrical multiple units (EMUs). The maintenance time of EMUs is limited, so the time left for partial discharge (PD) measurement of onboard cable termination is very short, leading to the obvious decreasing of detection accuracy. For addressing this issue, this article proposed a symmetrized dot pattern (SDP)-deep learning (DL) framework to detect the insulation defects using a time-series PD pulse signal. First, a PD measurement platform and the experimental samples were prepared in laboratory to obtain the time-series PD pulse signals of four typical insulation defects. Then, the time-series PD signals were converted into SDP images using the proposed parameter optimization method. Finally, the SDP-DL framework was proposed, and three specific and typical methods were utilized, i.e., convolutional neural network (CNN), stacked auto encoder (SAE), and deep belief network (DBN). The results show that the performance of the SDP-DBN method is the best, and the insulation defects can be detected with an accuracy of 96.1%. In addition, the visualization ability of data increases after SDP transformation of the original PD time-series signal.]]></description>
      <pubDate>Thu, 11 Jul 2024 13:53:13 GMT</pubDate>
      <guid>https://trid.trb.org/View/2201186</guid>
    </item>
    <item>
      <title>Monitoring of Insulated Rail Joints Based on Gap Value Measurement</title>
      <link>https://trid.trb.org/View/2362093</link>
      <description><![CDATA[The monitoring of an IRJ would allow targeted maintenance to be carried out, reducing the problems caused by its potential failures. The authors present the results of a test field investigation, that involved the installation of seven longitudinal displacement sensors that continuously record the gap value of insulated rail joints (IRJs). The monitoring of an IRJ would allow targeted maintenance to be carried out, reducing the problems caused by its potential failures. The studied monitoring system was installed in a station of the suburban railway line within the metropolitan city of Bologna (Italy). Analysis of low-and high-frequency recordings was performed. In particular, low-frequency acquisition was used to fit a statistical predictive model that detects a deviation from a standard behaviour and may evidence anomalies. For the high-frequency acquisitions (registered during train passage) some representative quantities, that can provide macroscopic indicators of loss of joint stiffness, were computed. Although gap measurement alone is not exhaustive for identifying all possible failure scenarios, the data acquired by these monitoring devices can represent a possible immediate monitoring solution, based on already available instrumentation, to provide user-friendly predictive analysis systems aiming at improving the railway maintenance.]]></description>
      <pubDate>Thu, 16 May 2024 16:38:44 GMT</pubDate>
      <guid>https://trid.trb.org/View/2362093</guid>
    </item>
    <item>
      <title>Method for Estimating Equivalent Salt Deposit Density on Insulator Surfaces Using Meteorological and Topographical Information Provided by Public Institutions</title>
      <link>https://trid.trb.org/View/2008854</link>
      <description><![CDATA[Traditionally, the design and maintenance of electric power facilities of electric railways in bay areas have been carried out according to a uniform classification of pollution based on distance from the coast and other factors. In order to improve the safety of these facilities and save labor for maintenance, it is necessary to subdivide this uniform classification according to the actual pollution situation. Therefore, the authors propose a method for estimating the Equivalent Salt Deposit Density on insulator surfaces at any point on an open section using meteorological and topographical information provided by public institutions.]]></description>
      <pubDate>Thu, 27 Oct 2022 13:47:00 GMT</pubDate>
      <guid>https://trid.trb.org/View/2008854</guid>
    </item>
    <item>
      <title>Study on the Modeling and Suppression of Arcing Generated by Articulated Split-Zone Insulator in Electrified Railways</title>
      <link>https://trid.trb.org/View/1933653</link>
      <description><![CDATA[In electrified railways, pantograph–catenary (PC) arc frequently occurs in the process of train passing through split-zone insulator, which threatens the current collection of PC and operation of electric multiple units (EMUs). So far, there have been a few studies on the analysis and modeling of the PC arc on split-zone insulator. It is noting that this research is different from that of split-phase region. This article first analyzes the dynamic variation process of PC distance as EMUs pass the insulator and deduces the formula, which can reflect the PC arc length variation according to the specific mechanical structure of insulator. Then, a black-box arc model of split-zone insulator is proposed. Next, a vehicle-to-grid model of the EMUs that contains the arc model of split-zone insulator is established to simulate and analyze the characteristics of the PC arc on split-zone insulator. Furthermore, the proposed arc model in this article is verified by comparing the simulated arc characteristic waveforms with the measured results. Finally, a sensitivity analysis of the arc model under different lifting angles of the contact wire is carried out in order to analyze the suppression of PC arc on split-zone insulator.]]></description>
      <pubDate>Thu, 19 May 2022 10:41:56 GMT</pubDate>
      <guid>https://trid.trb.org/View/1933653</guid>
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