CHAPTER 5
Mitigation Strategies

In some cases, the mitigation for IJ arcing is straightforward, and no modifications are required (e.g., repairing a loose cable connection). Other situations may use simple mitigations (e.g., adding a second cable bond at an existing bond location) and not require any other modifications. In other cases, determining the issue may require more effort and research, and multiple changes may be required to resolve the arcing issue.

The impact of the mitigations on the track, train control, traction power supply, and TPNR systems must be analyzed before implementation. Discernment is equally important in implementing the mitigations, and care should be taken to review the impact of the change at other adjacent locations, so the issues are not simply moved to the next adjacent IJ.

Sometimes the needed mitigations are more extensive (and expensive), such as adding additional track-to-track cross bonding or new cross bonds (which might require train control system modifications), adding impedance bonds, replacing existing impedance bonds with high-capacity impedance bonds, or running additional cables from the tracks to the TPSS.

In the end, the best mitigation is the one that is the easiest and least expensive to implement. In some cases, the most desirable or elegant mitigation is not always the best business decision or is so onerous it is not feasible. In other situations, the best mitigation may involve hiring a contractor to develop and bid a contract and perform the work, including dealing with long lead time material procurements, managing contract work, addressing impacts to revenue train operations, and more. In such cases, a second-best or less-elegant mitigation that may be sufficient to eliminate the arcing can be quickly implemented using existing forces and materials.

Educating Employees

Electrified railways are a complex system. There are various specialty disciplines and maintenance groups involved and responsible for maintaining various subsystems, but few understand the intricacies of all the various subsystems. To effectively maintain the overall system, all groups involved need to have at least a high-level understanding of the other subsystems to effectively perform functions in their area of responsibility. An understanding of how all the subsystems work and interact is critical to decision-making, prioritization, and determining how work is performed by all disciplines.

IJ Arcing

When IJ arcing occurs, it may be discovered by someone who can do nothing to mitigate the underlying issues. Employees should be able to recognize IJ arcing as a problem, understand it is not a normal condition, consider how it might impact their areas of responsibility, comprehend

that IJ replacement will not necessarily mitigate the issue, and decide how to escalate the issue. Appendix A features the Insulated Joint Rail End Inspection Guide, which is a tool that can be used to provide educated field personnel with information on how to identify IJ arcing and other unrelated IJ conditions.

Transit Vehicles

The communication of IJ arcing events should not be focused solely on those maintaining wayside equipment. When IJ arcing is found, communicating the conditions found wayside to those maintaining the vehicles is critical. IJs do not exist in isolation and are integrated components that interface with passing trains. IJ arcing events can damage train wheels, axle bearings, and other vehicle components. Some vehicle maintenance issues can be a contributing cause of the IJ arcing. IJ arcing damage to trains can easily be attributed to unrelated causes by vehicle maintainers, and the vehicle maintainers may not be aware of the misdiagnosis unless informed that IJ arcing has been found.

Personnel who inspect and maintain the vehicles should be educated on what conditions can contribute to, or be damaged by, the conditions that can lead to IJ arcing. Also, when wheel arcing damage, flash-burn indications, and other indications of TPNR overloads are found on transit vehicles, personnel should be taught to escalate the issue and communicate the problem to the workers who maintain the wayside equipment, so the root causes can be investigated.

TPNR Hazards

TPNR in the track can create significant electrical potential between the rails and other wayside equipment. While most personnel recognize the hazards from the supply side of the system (third rail or OHC), employees working wayside on electrified railroads also need to be educated on the hazards that may exist when working around exposed TPNR conductors, including running rails, cables, and other metal objects along the right-of-way. Understanding the electrical touch hazards that can result from simultaneously touching adjacent running rails or other insulated locations (e.g., switch rods, switch machines) is important to the safety of personnel working on electrified railways (Pham, Thomas, and Stinger Jr. 2003). Wayside personnel need to be trained in how to address TPNR hazards in the performance of their duties, including an understanding of the personal protection equipment required when working around TPNR.

Personnel working wayside need a good understanding of the possible differences in (1) electrical potential in the running rail, (2) devices connected to the running rails, and (3) earth ground, and earth-grounded devices, and creating electrical connections between adjacent running rails and tracks. An understanding of why and when additional tasks must be performed, such as applying temporary jumpers when cutting the rail or when performing maintenance on connections, is needed for those working wayside. A basic understanding of how the TPNR system works and the TPNR electrical potential that can be present, even when trains are not running in the immediate vicinity, is critical for employee safety and preventing damage to equipment when work is being performed.

Multidisciplinary Effort

Issue mitigation might require a multidisciplinary approach, except in cases where IJ arcing is caused by an obvious deficiency (e.g., defective IJ or loose cables). The TPNR system is complex and works in a delicate balance between the traction power system, train control system, track, vehicles, and train operations. Some IJ arcing issues cannot be resolved by a single group. In the development of this guide, transits and electric railroads that experienced IJ arcing but did not

have obvious causes were able to resolve the issue cost-effectively by taking a multidisciplinary effort; one group created a wide-ranging task force to guide the resolution efforts.

Commonly, the maintenance responsibility for IJs is delegated to the track department, but its ability to resolve IJ issues may be limited to simple replacement. IJ replacement seldom resolves IJ arcing, so personnel who are directly responsible for IJ maintenance can do little to resolve the issue. If the IJ arcing is generated because train operations exceed the design limits of the traction power system, little resolution, other than continued replacement of components damaged by the arcing, can be provided by personnel responsible for the traction power maintenance, track maintenance, or train control maintenance. When IJ arcing is identified and basic repairs fail to address the problem, a comprehensive multidisciplinary approach will likely be necessary to identify the underlying causes and develop the most cost-effective and timely solutions.

Insulated Joint Location Identification

Communicating and identifying the location of IJs can be challenging, particularly for communications across different disciplines. A transit can have hundreds or even thousands of IJs, and each discipline may have differing views on the identification of a particular IJ. IJs are an asset, and good asset management entails the unique identification of each asset. Asset management should begin during design when each IJ is assigned a unique identifier; that identifier should be shown on the drawings of every discipline that includes IJs on their drawings and marked during the field installation to facilitate coordination among disciplines. These identifiers can carry through from design to construction, operations, and maintenance, so IJ issues can be more easily communicated, coordinated, and tracked. Train control crews of one transit discovered a failed IJ that was causing an intermittent issue. The train control crews advised the track group and identified the location by interlocking designation and train control block. The track crews misinterpreted the location and replaced the wrong IJ. Because of the intermittent nature of the train control issue, it took some time to realize the incorrect IJ was replaced. Another project involved replacing all the IJs in a yard and adjacent main-line interlockings. In many cases, the IJs were replaced on one shift, and the subsequent required train control testing occurred on another shift. Miscommunication about the location of the replaced IJs resulted in the wrong train control circuits being tested, which created additional unnecessary work. The solution for these miscommunication issues was to assign a unique number to each IJ. The identifier was also marked on the rail at each IJ location. The drawings for the various disciplines were later updated to also show these IJ identifiers. Furthermore, each IJ, along with the track identifier and associated track circuit identifiers, was added to the maintenance database, thereby allowing the tracking of all work performed by various disciplines, departments, and shifts and the identification of problematic IJs that would have been not discovered otherwise. During design and construction, these unique IJ identifiers are invaluable for enumerating the number of IJs for cost estimation and managing test reports. Unique identifiers of IJs can also aid in communication of IJ arcing issues across all the affected disciplines.

Layered Approach

All the information related to the underlying causes of IJ arcing may not be readily available. A layered approach that includes performing the simplest and easiest tasks first, then, if the issue is not resolved, carrying out additional, more time-consuming tasks, may be the most effective strategy for IJ arcing mitigation. Mitigating quickly and easily identifiable causes for IJ arcing should be performed first (see Appendix C).

Table 1 shows a detailed checklist for resolving IJ arcing issues. Where arcing creates severe impacts, multiple tasks can be performed simultaneously. Some of the work required to resolve

Long Description.

Table depicts 14 items on the IJ arcing resolution checklist. Column headings from left to right are item, check, task, and description. Item 1 task is visually monitor IJs, and the description is monitor trains as they pass over IJs, noting when arcing occurs and the environment when the arcing occurs (e.g., position in train, train speeds, propulsion mode). Item 2 task is inspect IJs, and the description is inspect the condition of the arcing IJ, including other IJs in the vicinity. Item 3 task is inspect TPNR cables and connections, and the description is inspect the condition of the TPNR cable connections in the vicinity of the arcing IJ. Item 4 task is inspect train control devices, and the description is inspect the train control equipment that carries TPNR loads (e.g., impedance bonds) for poor electrical connections. Item 5 task is field verification of design, and the description is verify that field installation match the designs shown in the design drawings. Item 6 task is convene IJ arcing task force, and the description is if field inspections do not yield a solution to the IJ arcing issues, a task force should be convened. This task force should be multidisciplinary and include all the various maintenance and engineering disciplines impacted by the TPNR system; vehicle maintenance and train operations should be included. The task force can direct and prioritize future investigation and mitigation efforts. Item 7 task is review wayside maintenance records, and the description is review wayside maintenance records for unusual maintenance activities or repairs that may be related to the IJ arcing. This review should consider maintenance that can directly affect the TPNR system, cables, running rails, and more, as well as unusual maintenance history that may indicate side effects from IJ arcing (e.g., blown fuses in the train control system, flashing false occupancies in track circuits, self-clearing track occupancy indications). Item 8 task is review transit vehicle, and the description is review transit vehicle maintenance records for out of the ordinary issues related to the TPNR system onboard the vehicles, electrical overloads, blown fuses, arc damage to train wheels, arc flash damage to vehicles. Item 9 task is review control center trouble logs, and the description is review control center logs for trouble events that may be related to the IJ arcing, unusual problems with propulsions systems, propulsion system overloads, unplanned train stops, and more. Item 10 task is compare train schedule and operations, and the description is compare operating schedules of trains in the vicinity of the IJ arcing to determine the status of trains when arcing occurs. Recordings of train movements can capture the actual positions and operating modes of the trains that may be correlated to the location of the arcing IJs and are extremely valuable, if available. Item 11 task is review TPNR design, and the description is review the TPNR design and look for possible deficiencies in the design or the current loading or operations that may be leading to IJ arcing. Item 12 task is model TPNR system, and the description is use computer software to model the traction power network, including the TPNR system. The TPNR system should be modeled in detail, and the model should be based on the field-verified design drawings. Item 13 task is take field measurements, and the description is set up equipment to measure and record the traction power system, including TPNR. Simultaneous measurement of the train, including train speed, propulsion mode, power draw (voltages and amps), and onboard train TPNR voltage and current. Measurements should be made over arcing IJs at various speeds and in different propulsion modes. Recordings of the level of arcing and any rail-end arcing damage documents between train passes should be made simultaneously. Item 14 task is implement field modifications, and the description is if design modifications are required, they should be implemented only after a thorough interdisciplinary review to ensure the proposed modifications do not impact other systems or create other conflicts. Any changes made should also be documented on the affected drawings and, where required, field documents.

IJ arcing issues can take a lot of time, and tasks related to this work should be the last resort or performed in parallel with other tasks. If an issue causes critical damage, it may be necessary for train operations to be restricted or stopped over the affected routes until the problem is resolved. While operating restrictions can have significant impacts for patrons, continued unrestricted train operations may result in more substantial long-term impacts. Where it is possible to be wayside when trains are operating, feet on the ground and eyes on the IJ can provide valuable information about IJ arcing. Where it is not possible to be wayside at the same time trains are operating, the use of video recording equipment is a good alternative.