National Academies Press: OpenBook

Third Rail Insulator Failures: Current State of the Practice (2020)

Chapter: Appendix D - Case Example Interview Guide

« Previous: Appendix C - Case Example Questionnaire
Page 57
Suggested Citation:"Appendix D - Case Example Interview Guide." National Academies of Sciences, Engineering, and Medicine. 2020. Third Rail Insulator Failures: Current State of the Practice. Washington, DC: The National Academies Press. doi: 10.17226/26010.
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Page 57
Page 58
Suggested Citation:"Appendix D - Case Example Interview Guide." National Academies of Sciences, Engineering, and Medicine. 2020. Third Rail Insulator Failures: Current State of the Practice. Washington, DC: The National Academies Press. doi: 10.17226/26010.
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Page 58
Page 59
Suggested Citation:"Appendix D - Case Example Interview Guide." National Academies of Sciences, Engineering, and Medicine. 2020. Third Rail Insulator Failures: Current State of the Practice. Washington, DC: The National Academies Press. doi: 10.17226/26010.
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Page 59
Page 60
Suggested Citation:"Appendix D - Case Example Interview Guide." National Academies of Sciences, Engineering, and Medicine. 2020. Third Rail Insulator Failures: Current State of the Practice. Washington, DC: The National Academies Press. doi: 10.17226/26010.
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Page 60

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57 Case Example Interview Guide A P P E N D I X D 1. Interview Overview Metro rail systems use an electrified third rail to obtain traction power for the rail cars. The third rail is installed on insulators that get covered with steel dust, rust particles, brake dust, carbon dust, and other conducting particulates generated by operating trains. The particulates accumulate over time, causing the insulators to fail and resulting in leakage current, electric arcing, smoke, and fire. Insulator failures can cause delays in one portion of the transit system and have cascading effects to an entire metro rail network. Thousands of passengers can be delayed and stranded, increasing costs for passengers, businesses, and metro rail systems alike. Further, failure incidents can cause passenger concerns and discourage people from using metro rail systems. The problem is exacerbated by incidents occurring in tunnels. This synthesis will document the current practice and lessons learned from the use of the insulator systems and how transit systems prevent insulator failure. The document will include: • Third rail infrastructure specification and characteristics by agency (e.g., insulator materials, mounting configurations, type of contact rail, environmental factors, legacy vs. modern, newer systems, etc.); • Types and causes of failures (e.g., electrical. mechanical, operational); • Rate of failures; • Impacts of failure to agencies’ operations (e.g., manpower, costs, retention of customers, etc.); • Maintenance and failure mitigation methods. 2. Introductory Protocol This interview is intended to gather information on Third Rail Insulator Failures-Current State of the Practice so that transit agencies can learn from these experiences. Responses will be used to inform a Transit Cooperative Research Program (TCRP) synthesis that will document the

58 Third Rail Insulator Failures: Current State of the Practice 3. Questions 3.1. General Information 1. Would you please provide us with information about your title and responsibilities? 2. How is your work related to third rails? 3. Would you provide some general information about the transit system of the entity you are working for/with? For example, what are the specifications of your transit system (such as size, mode of transit system, etc.)? 3.2. General Information about Third Rail Insulators 4. How many of each type of insulator does your agency have in use in your system? Also, how many are inside tunnels and how many are outside tunnels? 5. Are clearance distances around and above the installation of the insulator distance the same for all types of insulators you employ? 6. What is the number of passengers commonly wasted per year due to third rail insulator failure in your track system? 7. Does your third rail system include safety considerations such as safety covers, brackets, or anchors for this purpose? If yes, please describe how this limitation affects the access to the insulators. 8. How much is the cost of maintenance of insulators? Also, can you compare the maintenance costs with the cost of insulator failures? 3.3. Voltage of System 9. What is the nominal traction power system voltage of your third rail system? 10. Does your system employ voltage regeneration? If yes, what is the typical maximum voltage that can be exhibited on your system during operation, whether by regeneration or other? 11. What is the rated insulator voltage and its dielectric withstand for wet and dry over- voltage? current state of the practice in Third Rail Insulator Failures. This interview includes questions about the status of deployment of third rail insulators at your agency and best practice strategies used for the insulator systems. If you have any questions, you may contact the project Principal Investigator, Dr. Sharareh (Sherri) Kermanshachi, at 817-272-2704 or sharareh.kermanshachi@uta.edu.

Case Example Interview Guide 59 3.5. Insulator Cleaning Methods 14. Does your agency adopt any specific surface cleaning technologies? Would you describe the adopted technologies in your agency? 15. How much time does it take to clean one insulator? 16. What are the drawbacks of the cleaning methods adopted in your agency? 17. If you are using a devise for cleaning insulators, is the insulator-cleaning device adjustable for different insulator sizes and types? 18. Did your agency develop any cleaning system requirements? If yes, what are the cleaning system requirements developed in your agency? 19. If your agency performs insulator cleaning, what is the implemented method for this purpose? Is there any reason for choosing this/these method(s)? 20. What are the common problems or difficulties the cleaners face when cleaning the insulators? 21. In your agency, how much time does it take to clean an insulator? (If it varies due to different types of insulators, please mention.) 22. If you have insulators in tunnels, is there any specific issue for cleaning such insulators? Note that the main issue may arise due to short space between the insulator and the tunnel wall. 3.6. Cost of Insulator Failure 23. Do you face leakage current in your system? Then, what is the annual electricity cost of leakage current in your third rail system? 3.7. Causes of Insulator Failure 24. Generally, and specifically in your agency, are there any specific causes of failure for third rail insulators? 25. Please specify if the installation method of all the insulators was the same or you used different methods. 26. In your system, do third rail cover boards have any impact on insulator debris buildup? If yes, please describe how third rail cover boards affect insulator debris buildup. 3.4. Features of Insulators 12. What is/are the mounting configuration(s) of employed insulators in your system? 13. In addition, what are the makes and models of the third rail insulators used in your system?

60 Third Rail Insulator Failures: Current State of the Practice 3.8. Consequences of Insulator Failures 28. What are the impacts of failure on your agency’s operations (e.g., on manpower, costs, retention of customers, etc.)? 3.9. Preventive Strategies 29. Would you describe the maintenance and failure mitigation methods that are implemented by your agency for the insulators? 30. Does your agency conduct research and develop improved designs and materials that might reduce the maintenance requirements of the insulators? If yes, how frequently are improved designs developed and/or are new materials selected? 31. Does your agency implement any scheduling methods to prevent automotive train control maintenance from being routinely deferred? If yes, what type of method does your agency employ? 32. Do the implemented regulations have any impacts on the safety program? If yes, how do the implemented regulations affect the safety program? 33. Does your agency use a model to guide inspections? If yes, how frequently does your agency update the model? Also, is this model risk-based by any chance? If yes, what are the considered risk factors in this model? Can you describe this model a little, please? 34. What type of new technologies does your agency employ to prevent insulator fires? 3.10. Replacements of Failed Insulators 35. Briefly describe the construction and installation process used in your agency to manage potential impacts of vibration, friction, rubbing, etc., on traction power cables. 36. Would you specify whether protective matting is used for cables lying along the ballast and tunnel invert in your system? How does it benefit the system? 37. Are there insulator materials or coatings that might be easier to maintain and clean? 3.11. Wrap-up 38. Are there any other issues that you would like to tell us or discuss about third rail insulator failures and the corresponding best practices for mitigating them? 27. Does saltwater from deicing roads adjacent to the tracks or over bridges drip or splash onto the insulators?

Next: Appendix E - Graphical Results of Survey »
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Third rail systems provide traction power to electrified rail systems in many parts of the world, including the United States, and encounter problems such as failures that need to be investigated and remediated.

The TRB Transit Cooperative Research Program's TCRP Synthesis 150: Third Rail Insulator Failures: Current State of the Practice documents the present practices and lessons learned, challenges, and gaps in information related to the use of third rail insulator systems in the United States. The synthesis delivers information that can assist transit organizations in making informed decisions about their third rail insulator systems and mitigation strategies.

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