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Posted 3 years ago

PantoSystem Implemented for Siemens eHighway Project

Automatic Train Supervision

    The customer The German government has introduced several initiatives to promote overhead contact lines for trucks, also known as eHighway. This solution makes road freight transport more energy-efficient and environmentally friendly [1] . The latter point is especially important and urgent, as the German government´s climate protection plan calls for reductions in CO 2 emissions by 40% from the transport sector by 2030 [2] . Since 2018 the Ministry of Environment in Germany is funding field trials of the eHighway system on real highway [3] . The challenge is to ensure that operations of this solution can be scaled up, which the users will be much more numerous as well as diverse. To prepare for this, the experience and solutions from PantoInspect were called upon. Germany’s transport ministry has announced the scaling-up phase of eHighway in Germany. Analysis from among other Germany’s National Platform for New Mobility (NPM) show that electrifying 4.000 km of motorways by 2030 is a cost-effective way to reach the climate targets. Analysis also shows the potential benefits of expanding the concept to neighboring countries such as Denmark and Sweden [4] . Ultimately, as contact line technology is in global use and climate change is a global problem, the objective is to spread the eHighway concept to the rest of the world. Since the eHighway project has come very far in the technical development stage, the team is now part of Siemens Rail Infrastructure, the division responsible for electrification of rail, and now also road. The eHighway project started in 2010 with the aim of developing two main components, namely the catenary system for use on motorways and pantographs for electrified trucks. In 2017, Siemens Mobility was commissioned up to €15 million ($16 million) by the German state of Hesse to build a 10 km overhead contact line for electrified road freight transport on a motorway. The eHighway project, which was part of one of the first three test tracks on a German motorway, running between the interchange Mörfelden (close to the Frankfurt airport) and the interchange Weiterstadt (close to Darmstadt).   The challenges/problems An important task to the eHighway team was to find a pantograph monitoring solution that was suitable for electrified trucks that could be connected to the overhead contact line. It was important for the team to have a system that could inspect the pantograph of the trucks to ensure the availability of the catenary system on the highway. Therefore, the eHighway team was looking for an inspection system that could help them detect defect pantographs to prevent potential damage of the catenary system. They also needed an inspection system that could help them detect if the pantograph is in an operating state and check that wear on the carbon strips was within an acceptable range. In addition, making sure that the pantograph had no other mechanical deformations that could potentially damage the catenary system. One of the main challenges was to find a pantograph monitoring system for electrified trucks, which could be installed above an overhead line in the highway environment. Electrified trucks do not have metal wheels, and therefore two pantographs are needed to establish two electric poles from which they can draw the power from. For this reason, pantographs on electrified trucks normally have four carbon strips and two overhead contact lines, unlike a train pantograph, which usually has two carbon strips and a single overhead contact line. Since the pantographs on the trucks contain more parts, the monitoring system required more sensors and technology than the usual system used for railways to ensure that the truck can leave the electrified lane and connect to it again.   The solution To ensure a high availability of an eHighway, it is important that no defective or worn-out pantographs will contact the overhead contact line. Since the operator of an eHighway System has no direct influence on the technical condition of the participating vehicles, it is very important to monitor the technical conditions of the connected vehicles. Siemens Mobility evaluated the Pantoinspect sensor system at the eHighway test facility in Groß-Dölln because the combination of camera and laser scanner provides the necessary basic requirements, for checking eHighway pantographs. With the results of the laser scanner, the geometric dimensions of the pantograph can be verified and compared with the limit values ​​stored in the Backend Monitoring System. Critical wear and tear as well as geometrical deviations can be detected and transmitted to the operation and control center. If necessary, an operator can use the high-resolution camera images to verify a detected deviation and inform the user that his pantograph is damaged, and the use of the overhead line is no longer permitted. The evaluation showed, that for a later series production some potential for optimization will be necessary, however the main task can be fulfilled with the PantoInspect portfolio.   Werner Pfliegl, Product Management of Siemens Mobility GmbH, Germany said: “PantoInspect was chosen by the eHighway team because the company has the advanced technical expertise and many years of proven track record in supplying some of the major infrastructure owners and rail operators in the global railway industry. The PantoSystem was very beneficial for the eHighway project since the team considered it as an all-in-one system that combines both a camera system and a laser system”.   The eHighway team also believed that the software was very good at providing statistical data to give the operator a detailed overview of the condition of the pantograph. PantoInspect carried out a lot of research and development to build up a model which was able to recognize every part of the pantograph on electrified truck correctly. The triggering system was also challenging in the beginning since the data on the speed of the vehicle needed to be found through the laser scanner itself to trigger the camera system correctly. However, PantoInspect managed to make extensive modifications to both the hardware and software to meet the requirements of the eHighway project.  The laser scanning device of the PantoSystem helped the team to build 3D models of the pantographs, which detected the working condition of the pantograph. The camera system was also used as a backup system to help the operator verify potential pantograph defects. They also believe that the system can help the owners of electrified trucks to get data on worn-out pantographs and ensure less maintenance of the catenary system as well as reduce the risk of damaged overhead contact lines. Siemens Mobility sees many advantages in using the PantoSystem for future applications in both electrified trucks and railways to help prevent an installed technical base from any type of damage. The team also see many future potentials in using the PantoSystem on 1000s of km of electrified tracks on motorways to evaluate the condition of the catenary system and for maintenance purpose. The system could potentially also help the BAG (Bundesamt für Güterverkehr) to identify electrified truck with defect pantographs, during their regular inspections, and thereby maximize safety on the highways. The PantoSystem can help Siemens offer a complete solution which includes both the identification of trucks as well as detection of defect pantographs, and thereby add great value to the company. This fits very well with PantoInspect´s vision of creating environmentally friendly solutions for both electrified railways and trucks.     About PantoInspect PantoInspect was the first company world-wide to develop an automated pantograph inspection system, in partnership with Banedanmark, the Danish railway infrastructure owner, around 2008. Today, PantoInspect is one of the world’s most recognized and respected brands and a market-leading manufacturer and supplier of automated and real-time Wayside Pantograph Monitoring systems to the global Railway industry. We have supplied several pantograph monitoring systems to some of the world’s leading infrastructure owners and rolling stock operators such as Deutsche Bahn, RATP, Infrabel, Sydney Trains, Network Rail, and TRA.     PantoInspect  Titangade 9C Copenhagen 2200, Denmark www.pantoinspect.com Email: contact@pantoinspect.com Tel: +45 3318 912       [1] https://www.bmvi.de/SharedDocs/EN/Dossier/Electric-Mobility-Sector/electric-mobility-sector.html [2] https://www.oeko.de/fileadmin/oekodoc/Climate-friendly-road-freight-transport.pdf [3] https://ec.europa.eu/jrc/sites/jrcsh/files/20201028_eu-hgv-workshop_sue_public.pdf [4] https://www.linkedin.com/posts/steen-n%C3%B8rby-nielsen-5736886_tysklands-transportministers-klimaplan-for-activity-6732401194108620800-6Ybn 

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Joanie Zhao -
Posted 12 months ago

#Tribute to railway maintenance workers#

Rail Tracks

When the train whizzes past Yellow figure flashing across the line of sight left to the railway workers The only impression of thousands of travelers They are the creator of high-quality lines Quantitative safety with millimeter precision Escort for the smooth operation of trains. For several decades Rail Maintenance and Repair Mode for Workers Technology, Machine Tools, etc. They are all quietly upgrading. Track bed, basic maintenance tools existing line Key words: #Ballasted track#, #Pickax#, #Pickaxe#, #Fork#, #tamping machine# Most of the existing railways have ballasted ballast beds, which are mainly composed of crushed stones. The stability of the ballast bed is poor and diseases are prone to occur. Therefore, operations such as screen cleaning, pillow replacement, tamping, and ballast repair accounted for a large proportion. For these jobs with a strong "metal smell", the tools used give the impression of "bulky". The legendary "old three pieces" are the "guy Shier" for the old road supporters to live and work, and it is the road supporters who use their sweat to ensure the safety of the railway operation. Tribute to the passers-by. Wuhan Linkage Track Equipment Co., Ltd. is determined to contribute to the safe operation of the world's railways. Our company provides a new generation of railway maintenance equipment. It can improve the working efficiency and make the workers work more easier. More details Please call 008615015909102。  

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Esat Kepenekli -
Posted 3 years ago

A Solution to the Impacts of Climate Change on Rail Infrastructure

Rail Tracks

The ability to detect the presence of a train on a particular stretch of track is a key enabler for automatic signalling, and hence modern train control. There are two types of technology generally used for train detection, a track circuit or an axle counter. Track Circuits also have a side function (usually without any commitments) to detect complete rail breaks to an extent with the employed impedance bonds, but they are not able to catch many of the broken rail cases, and the recent trend is to use axle counters instead of track circuits. There are many benefits of using axle counters in comparison to track circuits, like lower life-cycle costs, higher reliability, and better management of long sections. It should be noted that the widespread use of axle counters may provide great benefits for interlocking, however, the axle counters do not provide any information at all for whether the rail physical condition is in a safe state for train traffic or not. This means that when we start using axle counters, verification of rail condition with an additional monitoring system becomes vital to know whether there are any defects in the rails. If this aspect is neglected somehow, it seems quite likely that this can lead to disastrous consequences both for ASSET & PASSENGER SAFETY. The World’s Best Railway Infrastructure Owners are aware of the RISKS and they are searching for an Innovative & Accurate SOLUTION to the possible “Broken Rail” issues. Broken Rail Detection (BRD) systems are being offered to close the safety gaps related to the rail integrity monitoring aspects. And, early detection of rail flaws is being more vital each day, due to increased speeds in rail transportation, either for passenger or freight trains. If track circuits are used at a railway line, it is surely needed to deploy a supportive BRD system to close the safety gaps, however, if axle-counters are used, a reliable BRD system definitely becomes a “MUST-HAVE” for safe rail transport operation. The rail-mounted RailAcoustic® solution validates the health of the rail, identifies any breaks as soon as it occurs, and accordingly notifies the rail status immediately for the train dispatcher. RailAcoustic® thus increases throughput as tracks can be verified for operation instead of being blocked for days due to derailment accidents that can also have severe consequences. RailAcoustic® is designed for easy installation and track maintenance through the clamp mechanisms attached to the rail bottom without opening any holes or drilling on the rails. Its receivers identify even the partial rail cracks before a conventional track circuit could detect an electrical disconnect in the rail. Any complete break or a major partial break in the rail can be identified with a very accurate location within 100 m precision for safe train operation and ease of track maintenance. Rail-mounted RailAcoustic® components report to the back-office system to verify any detection. Messages are then passed to the signaling system or train control to take immediate action on the approaching or next trains passing the located breaks. This way, RailAcoustic® offers a near real-time detection and verification of breaks in rails – for safer and more profitable operation. The RailAcoustic® technology is demonstrated at High-Speed-Rail (HSR). The system is successfully in operation on a 90 km double-track stretch of the TCDD Konya High-Speed line, since 2018. Now, the installation and commissioning of the system continue for an 11 tunnel slab-track part (37 km) of the Sivas High-Speed line, to be integrated into the Siemens-provided CTC system. It is a proven, supportive, safety “enhancement” tool that does not need a SIL Certification in the short term, since it is not a component of mainline signalling but rather a very critical safety improvement for monitoring the RAIL and TRACK CONDITION. It solves a very critical issue in the railway industry with its methodology patented in the US, EU, China, Japan, India & Turkey, and has a great technical potential in the global rail industry subject to potential collaboration opportunities in different territories with diverse market needs. It has train monitoring abilities, which railway operators can benefit a lot. It is a result of 10 years-long research and development efforts that had been put in operation after extensive acceptance tests during the trial and commissioning phases of the client. The technology is unique and does not have any reasonable solution alternatives around the world offering a complete and stand-alone solution for high-speed railway lines, modernized conventional lines, and metro lines especially with continuously welded rails and limited ballast rock contact at the rail bottoms. Actually, as per the new approach with increased speed expectations in rail transport; it is obvious that a train should not be released to a line before being sure that especially the close segments of the tracks are safe for traffic. Only, then after "verifying the health status of rails and tracks", the interlocking and signalling come up to the fore, for a safe train presence monitoring and plotting of a route!  RailAcoustic® detects defects such as complete rail breaks and partial rail cracks, as well as other abnormalities like ballast washouts, floods, and landslides  The system 7/24 continuously senses: Partial Cracks on the Rails Complete Rail Breaks Significant Internal Defects Train Flat-Wheels Train Movement (with precise Speed info) Rail & Environmental Temperature Floods Landslides Washouts Buckled Rails Derailed Cars (only for low-speed freight rolling stock) The inventor and manufacturer of the system is Enekom, a technology company that is ready to be in collaboration with any parties, to enhance the safety of railways for protecting the assets and people. Please contact for further information: Esat Kepenekli – Contract and Commercial Manager Cell: +90 - 537 609 6498 (WhatsApp) Email: esatkepenekli (at) enekom.com.tr

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Nabayan Datta -
Posted 10 months ago

Advance Transportation

General

T ransportation is the most important aspect to know if you want to know the railway system very closely. 90% of railway employee and rail users have to gain a minimum knowledge about transportation, in whichever department they have been. Especially those who are from Operating and Commercial background, must have a core knowledge of it. Transportation have two parts i.e. 1. General Transportation, which are taught in all ZRTI for initial students and 2. Advance Transportation, an advance course for all traffic probationary taught in IRITM, Lucknow. In this topic, will going to draw an outline about advance transportation and discuss why all the students who are pursuing Rail Transport Management course, should gather knowledge about it. Transport Management is about a study of seeking vast knowledge about Railway's operational activities, commercial activities as well as traffic accountable activities. Advance Transportation covers the advance aspects of railway operation and analysis of day to day operating performance by applying numerous number of formulae and statistics.  Here are some below mentioned consideration of Advance Transportation and its outcome for learner:-  Freight train operations It is said that 65% of railway revenue are generated by selling goods service. Knowledge of freight train operations considered as a primary gateway to advance studies. It includes some essential points and indicates that can help the seekers to get a clear concept about freight business:- Knowledge of Transportation products offered by Railways to their customer Knowledge of the variety of commodities to be moved, with different characteristics & type of wagons required Knowledge of commodity rates enlisted by Indian Railway Conference Association(I.R.C.A)  Knowledge of Preferential Traffic Schedule and Rationalization Scheme published by Rail board in every year from 1st April under Railway Act. 1989 Knowledge of The activities of 8 core industries included Coal, Crude oil, Natural Gas, Petroleum refinery products, Fertilizer, Cement, Steel and Electricity generation and their relation with Indian Railways  Knowledge of Port Railway Management. Indian Railways gave Rail Transport Clearance(RTC) to all ports that they may build Private Port Terminal(PPT) with some policies generated by Rail board to ease the dock railway operation Knowledge of Container Rail operations, Container Rail Operators and their various policies, Container Class Rate(CCR) in which containers are charged to transport Knowledge of Various Running and Non Running Freight charges including Busy Season Charges, Hauling Charges, Wharfage, Demurrage, Punitive Charges, Congestion Charges etc.  Knowledge of various Freight Incentive Schemes published by Rail board to boost the freight marketing Knowledge of pattern and fluctuations in demand for rakes/wagons due to changes in the level of production, Seasonal variation of demand, pattern of Rake Allocation System in Indian Railways The Control Organization - The Nerve Centre of Railway system: As an organization develops and becomes more complex, the need for coordination between its various units becomes more urgent. The Control organization is one of the principal means by which this essential coordination is obtained in railway operation. Position of the Control officer in the railway organization can be compared with that of the brain in human body. Just like the brain, it guides all operations on the railway. The very skill of Coordination, Communication and Leadership can be seek out from this centralized organization.  C oaching train Operations  To operate coaching train, may not bring huge revenue to railway like goods train but we have to understood that operation of coaching train is a primary and fundamental duty of railway to society. Lots of advance consideration, theories, methods are included in this operation:- Various type of Coaching services served by Indian Railways to nation i.e. Suburban Service, Passenger Service, Mail/Express Service, Premium Service, Parcel Service, Railway Mail Service. Types and Characteristics of various Passenger Coaching Vehicles(PCV) and various Other Coaching Vehicle(OCV). Works and Activities of Passenger Profile Management(PPM).  Robust approaches of creating locomotive link for coaching train to ensure that no link would not be impacted due to failure of other link in the whole loco cycle.  Mathematical way of creating rake link in such manner that stabling time of any rake should be minimized and also to run more trains using less number rakes. Different approach of 'Punctuality' study including punctuality calculation formula, close study about factors which are affecting punctuality of passenger train.  Approach of creating Railway timetable and augmenting capacity utilization  It deals with some principles of timetabling and defines some notions of “good” quality of a timetable with respect to various stakeholders involved in a railway network (including passengers as end-users, freight customers and the network operator). This is followed by an elaboration on various parameters and how they affect the quality of a timetable.  Principles of rail-traffic timetabling.  Current timetable observations on some section. Capacity utilization of sections handling mixed traffic. Analysis of how various parameters affect congestion.  Junction congestion analysis. Recommendations for improvement in capacity. Distribution of slacks and allowances are made. Interchange management Ministry of Railway have 18 open railway zone, inter-connected by each other and each of them is a business module. Each railway owned a sufficient number of Rolling stock which are considered to be the most worthy assets as a transporter. If we consider the whole railway network as a business, then all the zones are considered to be investor. They used to invest their stock to play among the network. Their stocks juggled among the 18 zones by different interchange or Junction points. Any of the railway can use other's stocks for operational purpose. A fix amount of 'Hire Charges' are levied on debtor railways will be divided by among creditor railways in the proportion of their credits. Here the amount of credit depends on two figure, 1. Figure of Interchange Balance of a railway and 2. Figure of Wagon Balance of a railway. Proper and vivid way of interchange management helps to maintain a well balanced inter-railway financial adjustments. Beside wagon interchange, Coach interchange and loco interchange are also hire charged as per different rates.  Modernization and latest developments in Railway transportation Modernization means to modernize Railway to meet the challenges of economic growth, cater to the aspirations of common man, the needs of changing technology while ensuring at the same time socio economic requirements of the country. It includes Modernisation track, Strengthening bridges, Eliminating all Level crossings, Automatic signaling on busy routes, GSM based mobile train control system, Introduction of new generation motive power, Introduction high speed LHB coaches, Introduction of high haul freight wagon, Modernisation of major stations, Development of multi modal logistic parks, To set up real time information system, Attracting private investment through PP models for freight terminals, high speed railway lines, leasing wagons, coach and loco manufacturing renewable energy generation etc, Dedicated freight corridors, High speed trains, Increment of Avg. Speed of Goods train, Offering Graduate programme in Railway Technology about Advance Transportation. Various operating statistics and ratios  Advance Transportation are enriched with various operating statistics and ratios which are helps railways to express their service performance through mathematical calculation. TRAFFIC STATISTICS - included with Wagon loading, Wagon mobility Wagon Turn Round days, Wagon usage, Productive and Unproductive Service statistics, Wagon detaintion, Marshaling yard statistics, Terminal statistics. POWER STATISTICS - included with Engine usage, Engine demand, Engine utilisation, Fuel and Energy consumption, Engine failure statistics. ROLLING STOCK STATISTICS - included with Rolling stock holding and availability and Repair & Maintenance statistics.  Significance of Information Technology in Railway transportation system Think about this, within Indian Railways there are at least trains are running on daily basis, that means in each hour signals are being followed, points are being crossed over. Now imagine how stressful that operation would have been if it was ran by human. The system has to be up and running 24x7, with almost 0 tolerance and 0 lost time. We would have to have thousands if not million exceptionally skillful people to do this things day in and day out. And that's where the magic of Information Technology comes to play. The extensive use of IT systems increases the operability multiple fold, brings a transparent data of daily traffic activities and exposed as daily basis MIS report to stakeholders. In account of transportation lots of IT system are there:- Freight Operation Information System(FOIS):- For handling Operational and Commercial aspect of Goods traffic of Indian Railways Coaching Operation Information System(COIS):- Operational aspect of Coaching traffic  Punctuality Analysis and Monitoring Module(PAM):- Data collection of punctuality loss and analysis them Integrated Passenger Information System(IPIS):- A Integrated module of public addressing with proper running status of passenger trains Terminal Pipeline Management System(TPMS):- IT based prediction of terminal congestion of a particular freight terminal Station in accordance with pipeline flow, rake handling capacity over there. Time Table Module:- App based Time Table making modules of Indian Railways. Planning and Infrastructure (Traffic)  Whenever railway has intend to introduce a new traffic at their network, the consideration will be that, if there is a proper infrastructure to operate this train. The main objective of this, is to define the processes of managing the capacity of railway infrastructure with the aim of achieving high-quality operative management of traffic due to the efficiency of transport flow on the infrastructure. There are two ways of achieving high-quality, hassle-free traffic management, one is (i) By incurring expenditure and another is (ii) Without incurring expenditure. First one includes some important consideration like, increasing loading/unloading potential of the terminals to least the terminal detention, building long loop on long and heavy haul train operated sections, provision of shunting neck to all yard to ease the yard shunting without blocking mainline, provision of direct crossover in big junction station, auto signaling on congested section, provision of Bulb line to avoid train reversal, sufficient development in railway goods shed siding for rail users etc. Now, the planning without incurring expenditure be like efficient planning to augment section capacity, giving priority as per schedule, right powering of trains, maximizing long haul train, sufficient crew balancing at junction point with adjacent division, proper planning by board controllers etc.

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Mahesh Babu Nunna -
Posted one year ago

Artificial Intelligence In Railway

Signalling

        Introduction   Railway signaling is the process of controlling train movements to ensure safety, efficiency, and punctuality. The traditional railway signaling system is based on physical signals, such as colored lights and semaphore arms, which are placed alongside the track to communicate with the train driver. However, with the advent of modern technology, there has been a shift towards automated signaling systems that use artificial intelligence (AI) to improve safety and efficiency. In this article, we will explore the application of AI in railway signaling, its benefits and challenges, and the future of AI in this field.   Benefits of AI in Railway Signaling   Improved Safety AI can play a crucial role in improving safety in railway signaling. By using sensors and cameras, AI can detect obstacles on the track, such as fallen trees, animals, or even people, and alert the driver or activate the emergency brakes. AI can also monitor the speed and position of trains to prevent collisions and derailments.   Enhanced Efficiency AI can optimize train schedules and routing, resulting in reduced waiting times and improved punctuality. AI can also monitor and control the speed and acceleration of trains, leading to energy savings and reduced wear and tear on equipment.   Predictive Maintenance Predictive maintenance is another application of AI in railway signaling. AI systems can analyze data from sensors and other sources to predict equipment failures and recommend maintenance actions. This approach can reduce downtime, improve reliability, and extend the life of equipment.AI can help predict equipment failures and recommend maintenance actions, resulting in reduced downtime and improved reliability. By analyzing data from sensors and other sources, AI can detect potential issues before they become critical and schedule maintenance proactively.   Challenges of AI in Railway Signaling   Integration with Legacy Systems The integration of AI systems with existing railway signaling infrastructure can be challenging due to the complexity and heterogeneity of legacy systems. Compatibility issues, data formats, and communication protocols are some of the challenges that need to be addressed to ensure seamless integration.   Reliability and Safety AI systems must be highly reliable and safe, given the critical nature of railway signaling. Any failure or malfunction can have severe consequences, including loss of life and property damage. Ensuring the reliability and safety of AI systems requires rigorous testing, validation, and certification procedures.   Data Quality and Privacy AI systems depend on high-quality data to function correctly. However, data quality can be compromised due to various factors, such as sensor malfunction, environmental factors, or human error. Additionally, AI systems must adhere to strict data privacy regulations to protect sensitive information, such as train schedules and passenger data.   Integration of AI   The integration of AI in railway signaling systems is not without its challenges. Legacy infrastructure and compatibility issues can pose significant obstacles to the implementation of AI systems. Data formats and communication protocols vary between different signaling systems, which can hinder data sharing and interoperability. In addition, ensuring the reliability and safety of AI systems requires rigorous testing, validation, and certification procedures. Data quality can also be compromised due to various factors, such as sensor malfunction, environmental factors, or human error. Furthermore, AI systems must adhere to strict data privacy regulations to protect sensitive information, such as train schedules and passenger data.     Examples of AI in Railway Signaling   Autonomous Trains Autonomous trains are a significant application of AI in railway signaling. These trains use AI algorithms to control their speed, acceleration, and braking, allowing them to operate without human intervention. Autonomous trains offer several benefits, such as improved safety, reduced operating costs, and increased capacity.   Traffic Management Traffic management is another area where AI can be applied in railway signaling. AI algorithms can optimize train schedules and routing to reduce waiting times, improve punctuality, and increase capacity. AI can also monitor and control the speed and acceleration of trains, leading to energy savings and reduced wear and tear on equipment.   Real-time Monitoring Real-time monitoring of trains and track conditions is another application of AI in railway signaling. AI algorithms can analyze data from sensors and cameras to detect obstacles on the track, such as fallen trees or animals, and alert the driver or activate the emergency brakes. AI can also monitor train speeds and positions to prevent collisions and derailments.   The Future of AI in Railway Signaling   The future of AI in railway signaling is promising, with advancements in machine learning, deep learning, and other AI technologies. AI has the potential to revolutionize railway signaling by improving safety, enhancing efficiency, and reducing maintenance costs. However, to realize these benefits, railway operators must overcome the challenges of integrating AI systems with legacy infrastructure, ensuring the reliability and safety of AI systems, and maintaining data quality and privacy.   Conclusion   In conclusion, the adoption of AI in railway signaling systems offers significant benefits, such as improved safety, enhanced efficiency, and predictive maintenance. AI systems can use sensors and cameras to detect obstacles on the track, monitor train speeds and positions, optimize train schedules and routing, and predict equipment failures. However, railway operators must overcome the challenges of integrating AI systems with legacy infrastructure, ensuring the reliability and safety of AI systems, and maintaining data quality and privacy. The future of AI in railway signaling is promising, with advancements in machine learning, deep learning, and other AI technologies.

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Deepu Dharmarajan -
Posted 3 years ago

 CH25 | Modern Train Control Systems

CBTC

  1. ‘Communication’  Based Train Control Systems Train control has advanced from conventional fixed block system to moving block technology during the last three decades. Many highly dense cities realized the need for moving commuters in a large scale, especially during peak hours and frequent train operation under 3min or less is inevitable.. This is often referred as Headway among the Technical diaspora. Headway can be put it in simple words “The theoretical time separation between two Trains travelling in the same direction on the same track. It is calculated from the time the head-end of the leading Train passes a given reference point to the time the head-end of the following Train passes the same reference point”  It is possible to achieve tight 3 min headway with the help of automatic signalling ,however this is possible at the expense of  large amount of signalling asset maintained and less safety .Not forgetting the fact that Automatic train Protection system can be implemented for  safety enforcement but large number of standalone ATP system are getting obsolete  (Example :Hitachi L10000) within next decade .large scale greenhouse gas emission reduction also boosted the requirement for large scale passenger and freight movement with utmost safety and energy efficiency .Thanks to  Paris agreement often referred as Paris Accords adopted in 2015 .Headway requirements are relatively low for Mainline and freight however the need  for enhanced  safety and  efficiency are ever growing .There are pros and cons for the most popular train control systems . 2. Communication Based Train control System (CBTC) As per Institute of Electrical & Electronics Engineers (IEEE 1474 ) CBTC is a “A continuous automatic train control system utilizing high-resolution train location determination, independent of track circuits; continuous, high capacity, bidirectional train-to-wayside data communications; and trainborne and wayside processors capable of implementing vital functions” They do possess the following characteristics Determination of train location, to a high degree of precision, independent of track circuits. A geographically continuous train-to-wayside and wayside-to-train data communications network to permit the transfer of significantly more control and status information than is possible with conventional systems. Wayside and train-borne vital processors to process the train status and control data and provide continuous automatic train protection (ATP). Automatic train operation (ATO) and automatic train supervision (ATS) functions can also be provided, as required by the particular application It is not necessary that train shall be in unattended mode (driverless) to be identified as a CBTC. Any system that performs the above-mentioned functionality can be identified as a Communication Based Train Control System. Even though IEEE definition didn’t expect the need for a secondary train detection system, majority of the suburban network make use of a secondary Train detection system such as Track circuits or Axle counter for the degraded mode of operation in case the complete loss of communication. CBTC is mentioned as the train control system used in urban mobility  per IEEE definition rest of  this article ,even though European Train Control System or Positive train Control System also based on wayside to train communication. 3. Utilisation of Moving Block in CBTC Conventional railway system works on Fixed block system where each blocks are defined and separated with safe distance(braking distance)   with safety margin  and only one train possible in a longer block at a time and the leading  train has to clear the block before following train can occupy the block.Where as in moving block  train as a “moving block “ maintain safe distance based on braking curve with a safety margin .Refer below figure to identify the difference. There is an article  with comparison is posted in RailFactor ,and detailed comparison between traditional fixed block and moving block is out of scope for this article. Fig 1: Traditional Fixed Block System Fig 2: Moving Block System 4. European Train Control System (ETCS)   Evolved from the need for economic integration of the European Union for inter operation of their Trains .There were different signalling principles ,’non standardized ‘ signalling equipment existed in conventional system giving nightmare to operate between boarders with multiple train borne  systems(Turn off and Turn On )  to cross the boarder ,even crew were needed to change during boarder crossing  irrespective of same gauges between boarder. A technical specification for interoperability was embraced by the European parliament and the council of Union on the interoperability of the European rail system in accordance with the legislative procedure. Major Rail System providers from Europe known as Unisig companies under European Union Agency for Railways   jointly produced the rules  described in ‘Subsets”  .So far ETCS has five  levels (Application Level 0, Level NTC ,Level 1 ,Level 2 and Level 3)  as described in SUBSET-026-2 . Global System for Mobile Communications-Railway(GSM-R) is the  mode of data transmission between train and regulation centres (Wayside and Train borne) for ETCS Level 2 . Considering the fear that next 10 years will phase out the GSM-R  and various ETCS Level 2  implementation planned will impact.It could be implemented  with Long Term Evolution (LTE)  digital Radio System.LTE is normally regarded as 4G protocol  and the Future Railway Mobile Communication System (FRMCS) is considering to move something similar to 5G. Note :- European Rail Transport Management System ( ERTMS) include ETCS +GSM-R 5. Positive Train Control System (PTC) A communication-based Train monitoring and control system with a train protection system originated for the North America. As defined by AREMA (The American Railway Engineering and Maintenance of Way Association ) a Positive  Train Control System has the primary characteristics of Safe Train Separation to avoid train collision ,Line speed Enforcement ,Temporary Speed Restrictions ,Rail worker safety and Blind spot monitoring .As published in Digital Trends PTC work by ” combining radio, cellular and GPS technology with railway signals to allow trains to identify their locations relative to other trains on the track “Concept wise”  in a way PTC and ETCS are same. 6. East Japan Train Control (EJTC) Classified as four levels from Level 0 to Level 3 .Level 0 make use of an Automatic Train Stop device (ATS-S)  to prevent collision .This has been replaced with Automatic Train Stop device Pattern Type (ATS-P) in Level 1 addressing the weakness in ATS-S .New development with EJTC Level 3  make use of radio transmission and train itself detect its location and communicate with other trains .EJTC Level 3 is named as Advanced Train Administration and Communication System ( ATACS )  using Autonomous Decentralized System (ADS)  Technology. ADS technology is considered as most innovative modern technology for smart trains by Dr. Kinji Mori from Japan. This decentralized system composed of modules designed to operate independently capable of interacting each other to achieve the over all goal of the system. This innovative design enables the system to continuously function even when the event of components (modules ) failures .This plug and play module also enable  to replace the failed module while the overall system is still operational. Refer Figure 3  for message passing in an autonomous decentralized system.                Fig 3: Architecture for Autonomous Decentralized System      ADS  is a decoupled architecture where each subsystem communicates by message passing using shared data fields .Uniqueness of ADS system is that it doesn’t contain a central operating system or coordinator. Instead of that each subsystem manages its own functionality and coordination with other subsystems. When a subsystem needs to interact with other subsystems it broadcasts the shared data fields containing the request to all other subsystems. This broadcast does not include the identification or address of any other subsystem. Rather the other subsystems will, depending on their purpose and function, receive the broadcast message and make their own determination on what need to be done with it or ignore. Data transmission can be carried out by Enterprise Service Bus (ESB) .It operates in the autonomous decentralized system 7. Chinese Train Control System(CTCS) Largely based on ETCS except CTCS has Six Levels. China has a large rail network constitutes of several types of rail network such as High Speed, conventional, passenger and freights and realized the dire need for standardization, that is the basis for CTCS. Like ETCS ,CTCS also make use of balises on CTCS Level 2 and Level 3 .However Wuhan -Guangzhou high speed line uses ETCS Level 2 .China From year  2016 onwards  all metro lines in China are required to utilise LTE as the basis of their communications network. 8. Definition Standards for CBTC and ETCS This section depicts the major requirement specification for both the technology .Its recommended to refer these standards . In further chapters will cover case study and standard references for subsystems for each  elements to build a ETCS and CBTC systems . ETCS (All Levels) -ERA UNISIG EEIG ERTMS USERS GROUP SUBSET-026 - System Requirements Specification SUBSET -027 - FIS Juridical Recording SUBSET -034 - Train Interface FIS SUBSET-035 - Specific Transmission Module FFFIS SUBSET-036 - FFFIS for Eurobalise SUBSET-037 - EuroRadio FIS SUBSET-038 - Offline Key Management FIS SUBSET-039 - FIS for RBC/RBC handover SUBSET-044 - FFFIS for Euroloop SUBSET-047 - Trackside-Trainborne FIS for Radio infill SUBSET-056 - STM FFFIS Safe time layer SUBSET-057 - STM FFFIS Safe link layer SUBSET-058 - FFFIS STM Application layer SUNSET-098 - RBC-RBC Safe Communication Interface SUBSET-100 - Interface "G" Specification SUBSET-101 - Interface "K" Specification SUBSET 114 - KMC-ETCS Entity Off-line KM FIS SUBSET-137 - On-line Key Management FFFIS ERA_ERTMS_015560 - ETCS Driver Machine Interface   CBTC IEC 62290-1:2014- Railway applications - Urban guided transport management and command/control systems - Part 1: System principles and fundamental concepts. IEC 62290-2:2014-Railway applications - Urban guided transport management and command/control systems - Part 2: Functional requirements specification. IEC 62290-3:2019- Railway applications - Urban guided transport management and command/control systems - Part 3: System requirements specification. IEEE 1474.1 - Communications-Based Train Control (CBTC) Performance and Functional Requirments IEEE 1474.2 - User Interface Requirments in Communications-Based Train Control (CBTC) Systems IEEE 1474.3 - Recomended Practice for Communication-Based Train Control (CBTC) System Design and Functional Allocation IEEE 1474.4(Draft) - Recomended Practice for Communication-Based Train Control (CBTC) System IEEE 1482.1 - Rail Transite Vehicle Event Recorders IEEE 802.11 - IEEE Standard for Information Technology — Telecommunications and Information Exchange between Systems Local and Metropolitan Area Networks — Specific Requirements IEEE 29148 - Systems and software engineering - Life cycle processes - Requirements engineering - IEEE Computer Society IEEE 828 (Configuration Management ) - IEEE Standard for Configuration Management in Systems and Software Engineering IEEE 12207 (Software Life Cycle Process) - Systems and software engineering — Software life cycle processes IEEE 15288(System Life Cycle Process) - Systems and software - Systems life cycle processes IEEE 24748 (System &Software Engineering ) - Systems and software engineering — Life cycle management IEEE 802.3 (LAN Interface) - IEEE Standard for Ethernet 9. Comparison between CBTC and ETCS As mentioned before CBTC is based on Institute of Electrical & Electronics Engineers (IEEE) defined requirements where as ETCS is based on Subsets from ERA * UNISIG * EEIG ERTMS USERS GROUP.Refer Below table  for some of comparison between CBTC and ETCS solution. 10. Selection of System (food for thought !) It is also vital to select the best suitable solution for the rail network, especially brownfield based on your operational needs, track alignment, type of rollingstock operating on the line, whether track is laid on viaduct /at grade or Tunnel. Sometimes it could be tricky. Let me explain a complex scenario of a suburban network, with varying distance between stations which  could be in between  1km to 25km .It is currently operating with a fixed block system operating 12 Trains Per hour during peak time and 7 Trains per hour on non-peak hours and the  future patronage for the next 50 years are identified as 25- 28 train per hour during peak and 12 Trains during  non-peak hours  . Track is laid on Tunnel for some sections, and majority are either on ground  or viaduct /bridges. Network need to operate long freights on non-peak hours  which cannot be fitted with trainbourne equipments .It also shares main land trains with similar scenario on non peak hours . Network  has active level crossing  through out  the network .Below table detail some of the ideal solution in terms of cost (especially when many long sections are present ,implementing and maintaining  a DCS /Wifi will be expensive ) .What do you select as the ideal  solution in this scenario ?

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Suman Pathak -
Posted 2 years ago

Basic of MEP

General

  Basic of MEP MEP, or mechanical, electrical, and plumbing engineering, are the three technical disciplines that encompass the systems that allow stations/building interiors to be suitable for human use and occupancy. MEP construction must require all types of commercial, residential, and industrial purposes where services and facilities are required. MEP consists of installing air conditioning systems, water supply & drainage systems, firefighting systems, electrical power, and lighting systems including transformer substations and emergency power generators, fire protection and alarm systems, voice & data systems, security access, and surveillance systems, UPS, public address systems, Mast antenna TV system, and building management systems. MECHANICAL WORKS IN MEP PROJECT In MEP, major works are to be handled by Mechanical people because of HVAC or air conditioning system and that has piping work for cold and hot water, fabrication works for ducts, dampers and controllers, thermal/cold insulation works, and erection of machines like chiller unit, air handling units, grills, diffusers, etc. along with works of Drinking water, Drainage, and Sewerage systems. Other important Mechanical works are Firefighting works that included piping, sprinklers, and Pumps. ELECTRIC WORKS IN MEP PROJECT Electric works mainly included Electrical Power and Lighting but others like Transformer substations, Emergency power, UPS/Central battery, Voice/Data communication, TV, Security systems like CCTV surveillance system, Access control System, Public address system, Building management system (BMS), Fire alarm system, Surge Protection system, and Lightning protection system. PLUMBING WORKS ON MEP PROJECT Plumbing is a system of pipes and fixtures installed for the distribution and use of potable (drinkable) water, and the removal of waterborne wastes. It is usually distinguished from water and sewage systems that serve a group of buildings or a city.

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Deepu Dharmarajan -
Posted 3 years ago

CH1 | THE PURPOSE OF SIGNALLING

Signalling

SIGNALLING BOOK | CHAPTER 1 CONTENTS 1.Introduction 2.The Problems to be Solved 3.Basic Requirements 4.Lineside Signals 5.The Absolute Block System 6.Interlocking of Points and Signals 7.Single Lines 8.Further Developments 1. INTRODUCTION In general, the railway traveller assumes  that  his  journey  will  be safe. This  high  standard of safety which is taken for granted is the result  of  a  long  history  of  development.  As human errors and deficiencies in safety systems become evident, often as a result  of  an accident, improvements are made which are then incorporated into new generations of equipment. This is certainly true of railway signalling. It also appears to  be  a continuing  process.  We have not yet reached the situation where absolute safety can be assured. It is useful to start by looking back at some of the early history of signalling development. In the early days of railways, trains were few and speeds were low. The risk of a serious collision between two trains was minimal. Better track and more  powerful  locomotives allowed trains to run faster (requiring greater stopping distances). Railway traffic increased, requiring more and larger trains. The risks thus became greater and some form of  control over train  movements  became  necessary.  The need  for railway signalling had been identified. 2. THE PROBLEMS TO BE SOLVED 2.1 Collision with a Preceding Train When one train follows another on to the same section  of  line,  there  is a  risk  that,  if  the first train travels more slowly or stops, the second train will run into the rear of the first. Initially, trains were separated using  a system of  "time  interval"  working,  only  permitting a train to leave a station when a prescribed time had elapsed after the departure of  the previous train. Although this reduced the risk  of  collisions, a minimum safe distance between trains could not be guaranteed. However, in the absence  of  any proper communication between stations, it was the best that could be achieved at that time. 2.2 Conflicting Movements at Junctions Where railway lines cross or converge, there is the risk of two trains arriving simultaneously and both attempting to enter the same portion of track. Some  method  of  regulating  the passage of trains over junctions was therefore needed. This should ensure that one train is stopped, if necessary, to give precedence to the other. 2.3 Ensuring that the Correct Route is Set Where facing points are provided to allow a train to take alternative routes, the points must be held in the required position before the train is allowed to proceed and must not be moved until the train has completely passed over the points. Depending on the method of point operation, it may also be necessary to set trailing (i.e. converging) points to avoid damage to them. 2.4 Control of Single Lines Where traffic in both directions  must  use  the same single  line,  trains  must  not  be allowed to enter the single line from both ends at the same time. Although this could in theory be controlled by working to a strict timetable,  problems  could  still  arise if  trains were delayed or cancelled. 3. BASIC REQUIREMENTS We therefore have the basic requirements of any railway signalling system. The method of implementation has changed over the years but the purpose remains the same:- To provide a means of communicating instructions to the driver (signals) to enable him to control his train safely according to the track and traffic conditions ahead. To maintain a safe distance between following trains on the same line so that a train cannot collide with a preceding train which has stopped or is running more slowly. To provide interlocking between points and the signals allowing trains to move over them so that conflicting movements are prevented and points are held in the required position until the train has passed over them. To prevent opposing train movements on single lines. All the above requirements place restrictions on train movements, but it is vital that the signalling system will allow trains to run at the  frequency  demanded  by  the  timetable  to meet commercial requirements. This must be done without reduction of safety below an acceptable level. Signalling involves not only the provision of  equipment  but the adoption  of  a consistent  set of operating rules and communication procedures which can be understood and implemented by all staff responsible for railway operation. 4. LINESIDE SIGNALS It will probably be evident that the decisions regarding the movement of two or more trains over any portion of the railway can only be made by a person on the ground who has sufficient knowledge of the current traffic situation. His decision must be passed on to the driver of each train passing through his area of control. In the early days railways employed policemen whose duties would include the display of hand signals to approaching trains. As the policemen also had many other duties, it soon became impractical for them to be correctly positioned at all times. Fixed signals of various designs, often boards of different shapes and colours, were provided. The policeman could then set these and attend to his other duties. The simplest signals would only tell a driver whether or not he could proceed. From this evolved a standard layout of signals at most small stations; a "home" signal  on the approach side controlling entry to the station and a "starting" signal  protecting  the section of line to the next station. Between these signals, each train would be under the direct control of the policeman. These signals could give only two indications,  STOP  or  PROCEED. They therefore became collectively known as "stop" signals. As line speeds increased, "distant" signals were introduced which gave advance warning of the state of stop signals ahead. A distant signal could be associated with one or more stop signals and would be positioned to give an adequate braking distance to the first stop signal. It could give a CAUTION indication to indicate the need to stop further ahead or a CLEAR indication, assuring the driver that the stop signal(s) ahead were showing a proceed indication. With the addition of distant signals, trains were no longer restricted to a speed at which they could stop within signal sighting distance. It is important to understand the difference between stop and distant signals. A train must never pass a stop signal at danger. A distant signal at caution can be passed but the driver must control his train ready to stop, if necessary, at a stop signal ahead. The earliest signals were "semaphore" signals (i.e. moveable boards). To enable operation at night, these often had oil lamps added. With the advent of reliable electric lamps, the semaphore signal became unnecessary and a light signal could be used by day and night. Red is universally used as the colour for danger while green is the normal colour for proceed or clear. Initially, red was also used for the caution indication of distant signals but many railway administrations changed this to yellow so that there was no doubt that a red light always meant stop. If necessary, stop and distant signals can be positioned at the same point along the track. Alternatively, certain types of signal can display three or more indications to act as both stop and distant signals. 5. THE ABSOLUTE BLOCK SYSTEM Although time-interval working may seem crude, it is important to remember that nothing better was possible until some means of communication was invented. The development of the electric telegraph made the Block System possible. On many railways, time-interval working on double track lines is still the last resort if all communication between signal boxes is lost. 5.1  Block Sections In the Block Signalling system, the line is divided into sections, called "Block Sections". The Block Section commences at the starting signal (the last stop signal) of one signal box, and ends at the outermost home signal (the first stop signal) of the next box. With Absolute Block working, only one train is allowed in the Block Section at a time. The signalman may control movements within "Station Limits" without reference to adjacent signal boxes. The accompanying diagram shows a block section between two signal boxes on a double track railway. To understand the method of working, we will look at the progress of a train on the up line. Signalbox A controls entry to the block section but it is only signalman B who  can see a train leaving the section, whether it is complete (usually checked by observation of the tail lamp) and who thus knows whether or not the section is clear. Signalbox B must therefore control the working of the UP line block section. Similarly, signalbox A controls the DOWN line block section. 5.2 Block Bell The signalmen at each end of a block section must be able to communicate with each other. Although a telephone circuit is a practical means of doing this, a bell is normally used to transmit coded messages. It consists of a push switch ("tapper") at one box, operating a single-stroke bell at the adjacent box (normally over the same pair of wires). The use of a bell enforces the use of a standard set of codes for the various messages required to signal a train through the section and imposes a much greater discipline than a telephone, although a telephone may be provided as well, often using  the same circuit as the block bell. 5.3 Block Indicator This provides the signalman at the entrance to the  section with a continuous visual indication of the state of the section, to reinforce the bell codes. It is operated by the signalman at the exit of the block section. Early block instruments were "two position" displaying only two indications;  line clear and line blocked. Later instruments display at least 3 indications. The most usual are:- Line clear Giving permission to the rear signalman to admit a train to the section. Normal or Line Blocked Refusing permission. The signalman at the entrance to the section must maintain his starting signal at danger. Train on Line There is a Train in the block section. 5.4 Method of Working When signalbox A has an UP train approaching to send to box B,  the signalman at A will offer it forward to box B, using the appropriate bell code (so that signalman B knows what type of train it is). If the signalman B is unable to accept the train for any reason, he will ignore A's bell, and leave the UP line block indicator at "Normal". If he is able to accept the train, signalman B will repeat the bell code back to box A, and change the indication to "Line Clear". When signalman A sees  his  block  repeater go to "Line Clear", then he can clear his starting signals to admit the train to the section. When the train actually enters the section, signalman A sends the "Train Entering Section" bell code to box B. Signalman B will acknowledge this by repeating the bell code back to A, and turning the block indicator to "Train on Line". When the train leaves the block section at B, the signalman  there checks  that it is complete by watching for its tail lamp. He then turns his block indicator to "Normal" again.  He also sends the "Train out of Section" bell code to A, which A acknowledges by repeating it back. The system is now back to normal, ready for the next train. On multiple track railways, a pair of block instruments as above is required for each line. 5.5 Extra Safeguards The basic three-position block system, as described, relies on the correct sequence of operations for safety. A signalman could forget that he has a train in section and turn the indicator to "line clear", allowing a second train in. A detailed record (the train register) is kept of the actual times of train arrival and departure, and the times at which the bell signals are exchanged. In most places, additional safeguards have been added to the basic system. An  electric lock on the starting signal will prevent it being operated unless the block indicator is at line clear. Track circuit occupation may be used to set the block  instruments to ''Train on Line" if the signalman forgets to do so. Electric locking may also be used to ensure that signals are operated for one train movement only and replaced to danger before another movement is permitted to approach. Although it is unusual for absolute block working to be installed on any new signalling installation today, there are many railways on which it is in widespread use. The  block system, by ensuring that only one train may occupy a section of line at any time, maintains a safe distance between following trains. 6. INTERLOCKING OF POINTS AND SIGNALS On all early railways, points were moved by hand levers alongside the points. They could therefore be moved independently of the signals controlling the movement of trains. A great improvement in safety (as well as efficiency) was possible by connecting the point switches via rodding to a single central control point (the signal box). Similarly the signals could also be operated by wire from levers in the signal box. With the control of points and signals all in one place the levers  could be directly interlocked with each other. This had the following benefits:- Signals controlling conflicting routes could not be operated at the same time. A signal could only be operated if all  the points were in the correct position. The points could not be moved while a signal reading over them was cleared. In early signalling installations, all point and signal operation, together with any interlocking, was mechanical. Although it was a great technological advancement to be able to control a station from one place, the effort required to operate the levers restricted control of points to within about 300 metres from the signal box and signals up to about 1500 metres. At large stations, more than one signal box would often be necessary. The possibility still existed for a signalman to set the points, clear the signal, the train to proceed and then for the signalman to replace the signal to normal. This could free the locking on the points before the train had completely passed over them. Signalmen's instructions usually required the complete train to pass over the points before the signal was replaced to danger. 7. SINGLE LINES On most single line railways trains are infrequent. It is not normally necessary for two trains to follow each other closely in the same direction. Single lines were therefore treated in the same way as a normal block section with the important extra condition that trains could not be signalled in both directions at the same time. To enforce this condition and also to reassure the driver that he could safely enter the single line, some form of physical token was used as authority to travel over the single line. On the simplest of systems only one token existed. This caused problems whenever the pattern of service differed from alternate trains in each direction. If the timetable required two trains to travel over the single line in the same direction, the driver of the first train would be shown the token (or train staff  as  it is commonly  known) to assure the driver that no other train was on the single line. His authority to enter the single line would however be a written ticket . The following train would convey the train staff. Although workable, this system would cause problems if trains did not work strictly to the timetable. A further improvement was to provide several tokens, but to hold them locked in instruments at either end of the single line. The instruments would be electrically interlocked with each other to prevent more than one token being withdrawn at a time. The one token could however be withdrawn from either instrument. If the single line block equipment fails, many railways employ a member of the operating personnel as a human token. The "pilotman", as he is usually known, will either travel with the train or instruct the driver to pass through the section. No other person may allow a train on to the single line. Operationally, this is the equivalent of the train staff and ticket system described earlier. 8. FURTHER DEVELOPMENTS The main functions of the signalling system had now been defined, although they were to be continuously improved as the available technology developed. All  signalling  systems would be required to maintain a safe distance between trains, interlock points and signals and thus prevent conflicting movements, and provide the necessary information so that the speed of all trains can be safely controlled. In recent years, the signal engineer has been asked to provide further facilities within the general scope of the signalling system. These include, train information to the operating staff, train information for passengers, detection of defective vehicles, identification of vehicles and the increasing automation of tasks previously carried out by humans. The technology exists to completely operate a railway without human intervention although the level of automation desirable for a particular railway is for that railway administration to decide. Factors such as cost, maintainability, reliability, staffing policy, passenger security and sometimes political considerations must be taken into account. In many cases the final decision on the type of signalling to be provided is outside the direct control of the signal engineer. However, he should always endeavour to provide the best possible information and propose cost-effective solutions to particular problems so that the best decisions can be made.

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Deepu Dharmarajan -
Posted 3 years ago

CH10 | TRACK CIRCUIT BONDING

Signalling

TRACK CIRCUIT BONDING   CONTENTS   Introduction Fouling & Clearance Points Positioning of Insulated Joints Jointless Track Circuits Bonding of Rails Track Circuit Interupters  Other Information on Bonding/Insulation Plan NOTE: While these notes are based on the authors' understanding of railway signalling practice in New South Wales of Australia, they must not be taken to modify or replace any existing rules, instructions, or procedures of any railway administration. Where any apparent conflict exists, reference should be made to the appropriate documents produced by the administration of your Railway. This article will give fair bit of knowledge on bonding, there are numerous types of track circuits (FS2550, FS3000, CVCM, SDTC, TI21, MicroTrax). Bonding rules vary for these, and the respective manual shall be referred to. Bonding requirement for Axle counters is very limited (for Traction purpose only) and are out of scope for this article. 1. Introduction   A modem signalling installation will use many track circuits. The limits of each track circuit must be precisely defined, and the track circuit must be connected to operate safely and reliably, even through the most complex points and crossings. In many cases this will involve the installation of insulated joints, although jointless track circuits are available to suit many applications. An insulated joint is relatively simple to provide in jointed track. The fishplate and its bolts are insulated from the rail and an "end­ post", a piece of insulating material of similar shape to the rail cross section, is inserted between the rail ends. In welded rail, this operation is much more complex. Either the rail must be cut and an insulated joint inserted or a length of rail is removed and a pre-assembled joint in a section of rail is substituted. The rail is then welded. Both operations involve the adjustment of the rails to allow for internal stresses. After installation an insulated joint will generally be weaker than the rail on either side. Therefore, although insulated joints are essential, their position must be chosen correctly, and the number of joints minimized. In addition, it may be desirable to avoid joints in positions of greatest wear, vibration, or stress on the rails. The positioning of insulated joints may often be a compromise between the requirements for an ideal track circuit and the practicalities of permanent way construction and maintenance. For correct operation, the two rails of each track circuit must both be electrically continuous between all extremities of the track circuit. The rails must also be insulated from each other. This requirement is just as important through points and crossings as on plain line. There should be no position within a track circuit where a vehicle can be totally undetected. Each track circuit must operate reliably and must as far as is practical fail safe. Any normal failure mode should result in the track indicating occupation by a train. In areas where electric traction is employed, one or both rails will be used for the return traction current. The track circuit arrangement must permit an adequate traction current return path while maintaining safe operation of track circuits. In addition to the signalling plan, it is customary to prepare a plan showing the arrangement of the track circuits. Instead of a single line for each track, it will show each rail individually. Its main purpose is to show the bonding and insulation arrangements for all track circuits. In addition, it may show other useful information such as position of cable routes and locations, overhead structures, traction power supply connections, earth bonding and further details of the track circuit equipment.  2.      Fouling & Clearance Points Many insulated joints are positioned to prove clearance in the vicinity of points and crossings. The following terms will be used in these notes to describe the positioning of insulated joints. The fouling point is the position at which the extremity of a vehicle on one track is clear (by an adequate margin) of a movement on a converging line. The placing of an insulated joint at this position will not, however, ensure sufficient clearance. The clearance point is the position at which an insulated joint must be placed to ensure a vehicle stands beyond the fouling point. The distance of this from the fouling point will be determined by the longest overhang of all vehicles operating on the line. It follows that a joint which is intended to prove clearance must be positioned beyond the clearance point. although the signalling plan is not of adequate scale to show these joints accurately the track circuit bonding plan, or insulation plan, must be of a large enough scale to do so. If necessary, critical measurements must be taken from permanent way construction drawings. The limits of jointless track circuits cannot be precisely defined and cannot accurately determine clearance points. Even if jointless track circuit equipment is used through points and crossings, insulated joints will be needed to define clearance points and to electrically separate opposite running rails. 3.   Positioning of Insulated Joints   The positioning of insulated joints must fulfil all of the following requirements:- a) Within any track circuit, the two rails must always be of opposite. b) Unless adjacent track circuit signals employ different frequencies, the polarity (d.c. tracks) or phase (a.c. tracks) must be opposite on each side of all insulated joints. This is equally important whether the joint separates two track circuits or the two rails of the same track circuit. c) Where it is unavoidable to stagger block joints (i.e. they are not exactly opposite), the separation must be limited so that complete vehicles cannot remain undetected. d) Separation of a staggered pair of joints from an adjacent pair of joints (whether staggered or not) must not result in a vehicle being undetected. Critical clearance points cannot be defined by staggered. e) Minimum track circuit length must be greater than maximum vehicle wheel base. f) Maximum and minimum track circuit lengths must be within the specified range of operation of the type of track circuit. Most railways now employ a high degree of standardization of permanent way components. This will often restrict the position of insulated joints within points and crossings. Preferred positions must be used wherever possible to avoid additional cutting of rails and subsequent track maintenance. The use of these preferred positions will often result in joints being staggered. At a turnout, if there is a choice between joints in a high speed or low speed line, the low speed line is usually preferred. In cases where electric traction employs a single rail return, joints in plain line will usually be provided in one rail only. Pairs of joints will occur however in points and crossings and where it is desired to change the traction return rail from one side to the other. The above rules for staggering will still apply. In areas with double rail traction return, jointless track circuits must be used or joints must be provided in both rails, together with impedance bonds for continuity of traction current past the joint.   4. Jointless Track Circuits For adjacent jointless track circuits of the same type, no joints are necessary unless clearance points must be accurately defined. For replacement of signals and defining the end of an overlap, tolerances of 5-10 metres are usually acceptable. Adjacent jointless track circuits of the same type must be of different frequencies. Where a jointless track circuit adjoins a jointless track circuit of a different type, block joints will usually be needed due to different operating characteristics. A filter designed to operate with one type of track circuit is unlikely to discriminate correctly between signals of a different type of track circuit. Where any extremity of a jointless track circuit must be accurately positioned for clearance purposes, insulated joints must be provided. 5.  Bonding of Rails   Each rail must be bonded to give electrical continuity throughout the track circuit. The arrangement of bonding may be dependent on traction power supply arrangements. For fail safe operation feed/transmitter connections must be at one extremity of the track circuit and relay/receiver at the other. Between the feed and relay connections, the bonding must as far as possible be fail safe. If the rails are not welded together or otherwise bonded (e.g. for traction current) the signal engineer must provide adequate bonding throughout the length of the track circuit. The safest way of bonding the rails together is in series. On plain line this is the only practical method of bonding so no problems will arise. Within points and crossings, all track circuits will have additional branches which must also be bonded. All sections of a track circuit should still be bonded in series, but this may not be possible in all cases due to traction requirements. A certain amount of parallel bonding may be necessary. Figures 2 & 3   below demonstrate the difference between series and parallel bonding. In Figure 2, the rails in the turnout are parallel bonded. A break in any bond or rail in this section of track could leave a vehicle undetected - the track circuit will indicate clear when a train is standing on part of it. If the connections are rearranged as in the Figure 3, only very short sections of rail are now parallel bonded. Other than in these short sections, a break in a bond or a rail will cause the relay to drop, indicating an occupied track. Even in non-electrified areas, there will always be short branches of a track circuit which. cannot be connected in series (e.g. where the switch and stock rail adjoin). When the arrangement of track circuit bonding and insulation is being designed, the length of these branches should be kept as short as possible. 5.1  Non-electrified Areas It is usual, although not essential , to install insulated joints in both rails where electric traction is not used. In this case, series bonding should be employed throughout. To maximise the amount of series bonding, certain portions of rail through points and crossings may be common to two adjacent track circuits. In general, this should not cause a problem but in complex track layouts, the bonding and insulation must be checked very carefully to ensure that the use of a common rail between several nearby pairs of track circuits does not provide an electrical path for false operation of a track circuit and does not cause any track circuit to be shunted by trains outside its limits. Refer FIGURE 4 for a Track Circuit Sharing a common rail. 5.2.     Single Rail Traction Return   On many electrified lines, particularly those with a high voltage a.c. supply; traction return is via one rail only. The signal engineer still has exclusive use of the other rail. The two rails are normally designated the signalling rail and the traction rail. Of course, the signalling equipment must always use both rails. Track circuits connected in this way are described as single rail track circuits. The signalling rail will be series bonded. The traction rail must be connected to give the lowest impedance path back to the feeder station. Track circuits should be connected so that as much as possible of the traction rail bonding is in series. Often, however, parallel bonding must be accepted in the traction rail. A typical example of bonding for a single rail track circuit is shown on Figure 5. The signalling rail is connected to provide the maximum amount of series bonding. The traction rail shows a significant amount of parallel bonding. 5.3  Double Rail Traction Return   On Some lines, particularly those with d.c. traction, a lower supply voltage increases the traction current. This will often require both rails to be used for traction return.  Track circuits must therefore operate safely and reliably while sharing both rails with the much larger traction currents. To allow traction currents to pass conventional insulated joints, impedance bonds are used. Where two double rail tracks adjoin, the centre connections of the two impedance bonds are joined together. The ends of each coil are connected to the rails on either side. Where a double rail track circuit is of a jointless type, impedance bonds are not normally needed where tracks of the same type adjoin. At the end of a section containing a number of jointless track circuits, insulated joints are usually required and an impedance bond (resonated to the track circuit frequency) will be needed to pass the current around the insulated joint. Impedance bonds are also needed wherever the traction return must be connected to the supply at a feeder point and where adjacent roads are bonded together to reduce the impedance of the return path. Plain line track circuits are inherently series bonded.  Through points and crossings, however, if the double rail traction return is to be continuous, a proportion of parallel bonding is required. Although it prevents proof of continuity of the track circuit and its bonding, parallel bonding must be accepted as the only means of providing a low impedance traction return. Additional security is usually given by duplicating some or all of the rail-to-rail bonds (which of course will all be traction bonds and must consist of a suitably sized conductor).  Even in series bonded sections of rail, bonds or jumpers are often duplicated for reliability reasons. It must be remembered that maintenance routines must include regular checking of the integrity of these bonds because the disconnection of a single bond will not become evident as a track failure. Refer Figure 6 for Double Rail Track Circuit with Parallel bonding.    5.4.    Transition Between Single & Double Rail At the end of double rail sections, where they adjoin single rail track circuits, insulated joints will be required in both rails. An impedance bond will generally be needed for the double rail track. Its centre connection in this case will be bonded to the traction rail of the single rail track circuit. Refer Figure 7 for Typical Connections Between Single and Double Rail Track circuits. Where double rail tracks are in general use, even a small section of single rail return will increase the impedance of the traction return path. Single rail tracks in this situation are kept as short as possible. In some cases, two separate track circuits may be provided where a long track includes both points and plain line, even if one single rail track circuit could perform adequately over the total distance. 6. Track Circuit Interrupters   Track circuit interrupters are used to detect that a train has been derailed by a set of catch (trap) points by maintaining the track in the occupied state. The reason for this is that a derailed vehicle may be completely clear of the rails while still in a position which would be foul of other movements. If track circuit interrupters are provided, the following rules will generally apply to the track circuit bonding: - a)  The track circuit interrupter will be insulated from the rail upon which it is mounted. b) It will be bonded in series with the opposite rail to the one upon which it is mounted. c) Traction current should not pass through the track circuit interrupter. If mounted on a double rail track circuit, the interrupter must be connected in a separate circuit. A contact of the interrupter repeat relay must be included to cut the TPR circuit of its associated track. 7.  Other Information on Bonding/Insulation Plan   The bonding or insulation plan will often show other additional information such as:- a)  Position of overhead electrification structures. b) Bonding between overhead structures and traction return rails. c) Positions of locations, cable routes and signal structures.   Note : Please comment in the query section ,if you wish to discuss about  Bonding for Track Circuits like FS2500/FS3000, CVCM ,SDTC,TI21 etc on real layout . 

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Deepu Dharmarajan -
Posted 3 years ago

CH11 | SIGNALS AND TRAINSTOPS

Signalling

Coming Soon....

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Deepu Dharmarajan -
Posted 3 years ago

CH12A | CABLES

Signalling

CONTENTS         Introduction Signalling Cables Telecommunication Cables Power Cables Selection of Cable Type Methods of Termination Cable Routes Cable Construction Electrical Properties Cable Testing Data Cable Fiber Cables   INTRODUCTION Railway signalling now involves a wide range of equipment and techniques to transmit information, ranging from simple d.c. to carrier and data transmission. Associated with these is an equally wide range of interconnecting cables. Some are peculiar to railway signalling. Others are generally produced for telecommunications or general electrical purposes and have found applications within railway signalling. Refer Article Signalling Cable Standards on Rail Factor for a comprehensive list of cable standards, user of this article shall make effort to cross refer their current  local guideline/standard  in this regard.       2. SIGNALLING CABLES   Most lineside signalling circuits are d.c. or mains frequency a.c. Voltages are low, typically 24 - 120 volts. In some cases point machine can be 3 phase ,415/400 Volts ,3 wire system. Cables designed for conveying d.c. or low frequencies are generally far simpler than those for a.c. use. This is because the transmission of d.c. is far less demanding on the type and dimensions of the insulating materials and also on the construction of the cable. Under d.c. conditions the voltage drop along the cable conductor is the product of the current flowing and the resistance of the conductor. As long as the insulation material and its thickness is chosen such that its resistance is very high then it will have little or no effect on the voltage drop along the conductor. Although the electrical characteristics of most signalling cables will be similar, cable construction will vary according to the environment in which the cable is to be installed. The most common variants are:- 2.1 Internal wiring   This is usually flexible (stranded conductor) for easy installation along relay racks ,cable frame ,interlocking cabinets and cable ducts. The cable will generally be installed in a controlled environment so the sheath will not have to withstand such great changes in temperature, humidity and mechanical stresses as those installed outside. Many countries now have quite stringent requirements for the sheath material to satisfy fire regulations, the objective being to avoid emission of harmful gases in the event of a fire. Many existing internal cables have a PVC sheath. EVA (Ethylene Vinyl Acetate, otherwise known as Cross Linked Polyethylene) is often preferred now as it generally satisfies fire regulations. Some railways insist to use double sheathed insulation. Requirements for emission of smoke /and hazardous gas can be referred to IEC 61034-1/-2 and IEC60754-1 respectively. Similarly, IEC 60332-1 & IEC 60332-3 for flame test on Single wire and bunched wires respectively. UL1581 is an American Standard for electrical wires. Standard Size of wires are defined by AWG (American Wire Gauge)/European Or British Standards. Similar requirements exist for cables in tunnels and EVA sheathed cables are also used on underground railways. Internal cables are generally required as multicore cables (e.g. wiring between racks) and single core (individual circuits in interlockings and locations). Annealed Copper wires are used for electrical conductor compliant to IEC 60228(Australian AS/NZS 1574 & section 1&2 of 1125 ) 2.2 Lineside Cables Although these may carry similar circuits to the internal cables, they must withstand a more hostile environment. Typically, they will be installed in lineside troughs or buried and will be subject to changes in temperature and humidity, often lying-in waterlogged ground. Often UV Rays, oil, rodent and vermin will also be a problem. Individual conductors are insulated by an ethylene propylene rubber (EPR) compound/ while the outer sheath is polychloroprene (PCP) to give an oil resistant cable which will also withstand abrasion. If the cable requirement ask for UV Protection, Low Smoke Zero Halogen, Flame/Fire Retardant, carbon/iron/ wash plant liquid protection, outer sheath shall be selected accordingly . HDPE (High Density Polyethylene) cross linked polythene cover majority of such requirements. Most cables are multicore, to carry many separate signalling circuits. A single conductor will normally be adequate as the cable will not be subject to significant vibration once installed. Power cables are of similar construction but generally consist of two cores (for d.c. or single phase a.c. distribution and will generally have a stranded conductor due to the cross-section required. Some railways favour some form of armoured sheath (e.g. steel wire) for added mechanical protection. 2.3 On-track Cables Trackside electrical equipment is generally connected by cables across or under the ballast. Such cables must be strong and capable of withstanding considerable vibration. British Railway uses a flexible, multi-strand cable. Materials and construction are as for the lineside cables above, but the sheath is thicker, and the conductor is composed of a larger number of smaller strands (50/0.50mm).    Again, many railways prefer an armoured cable but this can also present problems with earth faults where the risk of damage to the cable is high. 3.TELECOMMUNICATION CABLES   Under a.c. conditions the inductance and capacitance of a cable can have a considerable bearing on the voltage drop and these factors become of major importance as the frequency increases. The capacitance of a cable pair or conductor will depend on the type and thickness of the insulation material. For a given material the thickness required for ac. transmission will generally be greater than for d.c. transmission. Suitable insulation materials for a.c. cables are dry air, paper and polythene. P.V.C. and rubber are not considered to be satisfactory, except in the case of low frequency cables such as 50Hz power. With multicore cables there is the additional problem of interference in one circuit due to the current in a neighboring circuit, commonly called "Crosstalk". The degree of crosstalk which may be encountered can depend on a number of different factors e.g. a) The frequency of the disturbing signal e. crosstalk increases with frequency (square waveforms, because of their high harmonic content are particularly troublesome). b) The magnitude of the current flowing in the disturbing i.e. crosstalk increases with the current. c) The position of the conductors in the cable relative to each To satisfy the latter problem, cables are manufactured with cores twisted together to form pairs, and adjacent pairs may be twisted at different rates. A circuit should always utilise the two conductors of a pair for out and return. Common returns should not be used in such cables. The effect of twisting the conductors together in such a fashion is that cancellation of any induced voltage occurs across any load terminated at the ends: of the cable pair.  Often cables are made up in multiples of quads instead of pairs. In such cases a pair is formed by utilising the diametrically opposite cores. The resultant cable is smaller in diameter than the equivalent multi-pair cable, since there is less wasted space within the cable. With the use of very high frequencies on carrier circuits and for broad bandwidth applications such as closed-circuit television, the problems of crosstalk and attenuation increase with frequency. Eventually, twisted pair cables become unsatisfactory. Coaxial cable, effectively a cable pair consisting of a central conductor surrounded by and insulated from an outer metallic sheath, is employed. The fields created by the high frequency signals are contained in the cylindrical space between the inner and outer conductors, thus alleviating the crosstalk problem. A larger spacing between conductors also reduces the high frequency attenuation. 4. POWER CABLES For both signalling and telecommunications applications it is necessary to distribute power to the lineside. For most purposes this is best distributed as a.c. and transformed and/or rectified locally to the equipment served. A wide range of power cables is manufactured to supply the electrical industry, and these are generally employed within signalling and telecommunications systems. The sheath and/or insulation material may have to be modified to suit the specifications for signalling cable. As most power distribution is single phase, 2-core power cables are generally used. The conductors may be stranded copper or solid aluminium.   5. SELECTION OF CABLE TYPE   5.1 Lineside Signalling Circuits Signalling circuits will be taken to mean d.c. or mains frequency a.c. circuits between an interlocking and a lineside location (or between locations) to convey signalling information. They are normally laid in main cable routes and may be very numerous in areas of complex        signalling. Cables for signalling circuits normally utilise conductors with only one strand, as mechanical strength is not of major importance. Typical cross sectional area is 0.5 to 2.5mm 2. To economize on installation costs, a smaller number of cables with a higher number of cores is preferred. 5.2  Tail Cables   On-track cables (tail cables) to lineside equipment (e.g. signal heads, point machines etc.) from relay rooms or location cupboards must withstand physical damage and vibration. The B.R. standard cable has 50 strands to give it flexibility and a heavy-duty sheath for protection. The following sizes are commonly used: 5.3 Power Distribution   Standard industrial sizes of 2-core power cable are used. The size of the conductors will depend on the power loading and the consequent voltage drop along the line. For most types of signalling equipment, a voltage drop of 10% is usually the maximum acceptable. It is therefore important to perform an estimate of power consumption of all equipment before deciding upon the size of cable to install. Allowance should be made for possible future additions to the electrical load. Renewal of power cables at a later stage can be expensive. 5.4 Internal Relay Room/Location Wiring   Due to the diverse termination points of internal circuits, the only means of installing internal circuits is to use individual wires. Cables may be useful for wiring between racks or between different rooms/floors of a building to simplify installation by allowing factory pre- wiring. Alternatively, armoured (e.g. steel wire) cable could be used. This has fallen in popularity in recent years due to cost, difficulty of handling and difficulty in performing a satisfactory repair in the event of damage. 6 . METHODS OF TERMINATION   All cables and wires must be terminated to connect on to other equipment. Each individual conductor in the cable will normally be terminated, even though some cores may be spare. In addition to terminating the individual cores the cable sheath is often clamped to a fixed bar in the location or equipment room. This is to avoid the weight of the cable placing a strain on the individual terminations which could lead to breakage of the conductors. The following are the most widely used forms of termination: - 6.1  Crimped Termination   This method is mainly used for stranded cables. It is unsuitable for small cross-section single conductors as it weakens the conductor mechanically. It is  a  mechanical  method which involves compressing a metal termination on to the wire. Various types of crimped connector are available:- a) A "ring" type connector to fit over a screw terminal. This is secured by nuts and washers. b) "Spade" type connectors which can be inserted into equipment terminals without the need to completely remove nuts and washers. c) A special type of spade connector for use in BR930 relay bases. These are simply inserted into the relay base. The crimps are constructed so as to spring apart slightly and lock the wire in position. A special tool is required to extract this type of connector d) "Shoelace " type connectors which can be inserted into equipment terminals without the need to completely remove nuts and washers. There are terminals available capable of inserting wires without the need of ferrules. Its recommended to use ferrules for multi stranded wires, however single wire cores can be inserted without a ferrule. For all types of crimped connection, it is important to choose the correct size to suit the terminal, the size of conductor and the size of insulation. Its also important to ensure the terminal can withstand the current carrying capacity of the wire. 6.2  Screw Terminals   These are used in conjunction with crimped terminations or to directly terminate the conductors of solid cored cables. The cable is held tightly by a screw and/or nuts and washers to provide mechanical strength and electrical continuity. Where screw terminals are used, it is common to provide disconnection links to enable portions of the circuit to be isolated. 6.3  Plug Couplers   Where modular equipment requires to be unplugged it is common to connect all wiring to a plug coupler. Wires may be soldered or wire-wrapped for security. This allows very quick disconnection and reconnection and avoids the need to check and/or test the wiring when a module is replaced. Plug couplers are often electrically or mechanically coded to ensure that they are only connected to the correct equipment. 7. CABLE ROUTES   A safe route must be determined for the cables, both within buildings and externally. Within buildings, suitable ducts may be provided as part of the building or the equipment racking. If the cable route is shared with other than signalling cables, it must be ascertained that there is no hazard from electrical interference. Outside buildings there are several methods of cable installation used. These are described below. 7.1 Troughing   Troughing is laid on the surface. It is usually inset into the ground for stability and the safety of staff walking along the track. Cable installation is simple. The lids are removed, the cables placed in the trough and the lids replaced. Two types are now in common use:- a)  Ground Level Sectional Concrete Troughing. b) Ground Level Plastic Troughing. Plastic troughing is easier to handle but requires more accuracy in installation. Lids must be clipped on rather than being held in place by their own weight. 7.2  Ducts The following types of cable duct are in general use:- a) Earthenware duct  b) Thick wall Rigid V.C. duct c) Thin wall V.C. duct. This duct must be laid in concrete d) Asbestos Cement duct - not generally available but has been used in the past in large quantities. e) Steel duct f) Flexible plastic pipe - this is corrugated along its length to allow the pipe to bend  A common problem with all ducts is that over a long period of time they tend to accumulate debris which is either washed or blown into them. After a long period of time has elapsed, this may make further cable installation more difficult. 7.3 Cable Racks or Trays   Slotted steel or plastic trays may be fixed to lineside structures, retaining walls etc. Cables may be fixed to this using plastic cable ties. The cable route is easily accessible for installation purposes but is also exposed to the environment and may be unsatisfactory in areas where vandalism is a problem. A similar method is to use cable hangers - hooks on to which the cable is placed and held in position by its own weight. This method is particularly useful in tunnels where there is little risk of vandalism and clearances are limited. 7.4  Buried Cables   Provided the cable sheath is suitable cables may be buried direct in the ground. This avoids the cost of providing an expensive cable route. Cables are normally buried in one of two ways:- a) Laid in a trench with protective tapes or tiles and backfilled. b) Mole ploughed using a mechanical mole ploughing machine. In both cases warning markers should be provided on the surface at regular intervals. Buried cables suffer from several problems:- a) It is difficult to install further cables at a later stage without risk of damaging existing cables. b) Cables are vulnerable to excavations by others as they are not visible. Cable markers may eventually become obscured. c) Fault location and rectification is more difficult. d) Over a long period, ground movements and the growth of tree roots etc. may stretch and damage the cables. When specifying the type of cable installation, the engineer should take all costs, risks and benefits into account. 7.5   Aerial Cable Where an existing pole route is in good condition, it may be economic to install aerial cable. Aerial cable is however vulnerable to damage (gunshot, falling branches etc.) and the effects of lightning. Ordinary cable is unsuitable for aerial installation. Aerial cable has a steel strainer wire installed to provide the necessary tensile strength for hanging on poles. 7.6  Application   In general the application of the above methods are as follows:- 7.6.1 Track-side cable routes   Ground Level Concrete Troughing and Plastic Troughing is usually preferred where a large number of cables is required. Burying may be employed for small cable routes (i.e. single lines). Aerial cable could be considered if an existing pole route is still in good condition and the risk of damage or interference is low. 7.6.2 Under Track Crossings Practices vary but in general steel or asbestos cement ducts are preferable because of their ability to withstand vertical impact. In some cases thick wall P.V.C. duct has been used. Ducts should be installed sufficiently far below the track to be clear of track maintenance equipment (tamping machines, ballast cleaners etc.). 7.6.3 Platform Routes   In general, platform routes should be provided with cable ducts and associated manholes for access to joints and pulling through of cables. Usually, it is more convenient to use earthenware ducts for platform routes. Surface troughing or hangers along the platform edge may interfere with track maintenance. 7.6.4 Tunnels The method used will depend upon the construction and cross section of the tunnel. It is often difficult to install a ground level route which will be clear of track maintenance machinery. Cable trays or hangers on the tunnel wall are therefore the most suitable. It is of course possible to design new tunnels to accommodate a cable route. Whether this is best located on the tunnel wall or floor will be determined by the type of track and tunnel drainage requirements. 7.6.5 Tail Cables   Opinions vary on the best method. It is unlikely that there is a best method which suits both the signal engineer and the permanent way engineer. Cables may be simply laid across the top of the ballast. These are visible and easily removed and replaced. They are also vulnerable to damage by track maintenance and trailing objects on trains. Use of surface level ducts provides added protection but interferes with track maintenance. Placing the ducts below ballast level increases installation costs. Ducts can also become blocked with ballast and other debris. Surface cables secured to the top surface of the sleepers have greater protection than those laid loose across the ballast. This method may not always be acceptable to the track engineer. Tracks laid on concrete sleeper can use hard hats to cover the cable where hard hats are fastened on the concrete. 8.  CABLE CONSTRUCTION   A vast range of cables is now available. it is only possible to cover some of the main features of modem signaling cables in this section. There are many other cables widely in use for different application including control voltage to a Point Machine. Refer Figure 2 for the construction of a modern quad cable with Water Resistant property. Even though below section is based on Quad Cable Construction, we use this opportunity to discuss other alternative options available for armour, screen, internal & external sheath and the conductor insulation. Selection of PVC materials (XLPE -Cross Linked Polyethylene, LDPE -Low Density Polyethylene HDPE -High Density Polyethylene) and the addictive included for UV, Pest, Carbon /Iron /Copper/Mineral Dust, Acid /Salt, Industrial Cleaning solution    shall be selected according to the operators need and the type of environment for the intended application. It is signal engineers’ responsibility to ensure that cable will not fail and select the property in case operator doesn’t specify detailed requirement. 8.1 Conductor Materials   Copper is the most widely used conductor material due to its very low resistance and excellent mechanical properties. It is also available in sufficient quantities at an acceptable price. The copper is manufactured as wire of a consistent cross-section by repeatedly drawing the copper through holes in dies of reducing cross-section until the desired size is reached. As this process tends to harden the copper wire, it is usually annealed to restore its ductile properties. Annealed copper wires are complied to EN60811-203 /IEC 60228 .Refer RailFactor Article “Standard for Signalling cables “ as well for more details. Where rubber insulations are employed, the copper is generally coated with tin to prevent a chemical reaction between them causing corrosion of the copper and a change in the mechanical properties of the rubber. Where a large cross-section is required, aluminium may be used in place of copper (e.g. for power cables). Although Aluminium is more resistive, it is lighter and cheaper and has greater mechanical strength. Aluminium cables generally employ a solid conductor and are therefore more rigid than the copper equivalent. 8.2  Insulating Materials   Each core of a cable must be insulated from all others and must therefore be surrounded by an insulating material throughout its length. Signalling cables use thermoplastic (P.V.C. or Polyethylene) or elastomeric (natural rubber or polychloroprene (P.C.P.)) insulations. The addition of P.C.P. to rubber improves its resistance to weathering. In very wet conditions, however, it has a tendency to absorb water over a long period of time. This will adversely affect its electrical characteristics. With telecommunications cables, the capacitance between cores becomes significant with a.c. signals. Dry air is the best insulator but impractical for cable construction. In older cables paper was widely_ used. This effectively consisted of a mixture of organic fibres and a large proportion of air spaces. As paper insulation is no longer used, polyethylene ie: HDPE (High Density Polyethylene-Solid) insulation is common these days with Low Smoke, Zero halogen property especially in the tunneled application. 8.3  Formation of Conductors Quad formation of conductors are the most recent trend for multicore cables .They are constructed in 1 Quad (4 Core ) ,3Quad (12 Core) ,4 Quad ( 16 Core ) , 5Quad (20Core ), 7Quad( 28Core) and 10Quad ( 40 core) .Each quad is arranged in the form of a Star (Diamond)  and twisted together to get the best electrical property in terms of mutual Capacitance ( <45nF/Km) and Electromagnetic Compatibility compared to other formation which makes higher mutual capacitance .Lightly twisted pair formation is also available  for better Electro Magnetic Compatibility. German DB(DB416.0115-Standard) defined Quad cable is popular for CBTC /ETCS application. Quads are helically stranded in concentric layers and cables more than 7Quad include two extra conductors with perforated insulation for surveillance. Signal Engineer shall select the compatible cable with respect to their signalling solution. 8.4   Core Identification Cores are identified in a number of ways, for a DB defined Quad Cable as shown in Figure 2 on light brown  conductors black bracelets are printed in different combination .Eg: Two black circles printed  together and repeated on  fixed length apart ,One circle  printed and repeated on certain length etc . As a Designer I am not a big fan of such identification as its confusing for the technicians for the first time. Methods of identification can be classified into 5. a)       Coloured Tape wrapped around each core b)       Coloured Insulation (Especially for Signalling Application Power Cables) c)       Numbered Tape d)       Numbering Printed on the insulation. e)       Identification concentric rings (as mentioned above  on DB defined Quad Cable) When numbering is used care must be taken to avoid confusion between 6 and 9. The easiest method is to write the number (six or nine) as well as or instead of the numerals. Various systems of colour coding are used depending on the size, type and manufacturer of the cable. In a paired cable only one conductor may be colour coded. The numbering of cable cores/pairs always starts from one at the centre and increases towards the outside of the cable. Each end of the cable is identified - the A end is the end at which the numbering of each layer runs in a clockwise direction, the opposite end is the B (or Z) end. 8.5  Core Wrapping, Screen, Inner Jacket, Swellable Tapes & Armour Plastic tapes are overlapped around cores which collectively hold all the cores together, on top of it, a copolymer coated aluminium tapes are wrapped. Tinned copper wire of 0.5 mm. run along the cable making in contact with the aluminium tape. This arrangement provides the functional earthing (EMC) option for the cable. This continuity wire needs to be earthed along with the armour for earthing the induced current generated due to parallelism (double sided for AC Traction line and singe sided for DC Traction). This arrangement is protected with Black coloured Zero Halogen Low Smoke compound PVC Inner jacket. Steel Tape armour is   taped around the inner jacket. Swellable water blocking tapes are wrapped around the Inner jacket and Steel armour to avoid longitudinal water penetration. This arrangement along with inner and outer sheath is making the cable compliant to moisture barrier requirement per BS-EN 50288-1, EN 50288-7 or equivalent, water immersion test complying to IEC 61156-1. This construction is ensured to pass the Transversal water tightness and armour long water tightness test according to EN50289-4-2/A and water absorption for conductor insulation and outer jacket according to EN60811-402. 8.5.1 Types of Armour Armour provides additional mechanical heavy-duty protection, such as crushing, and resistance from pest such as rodent penetrating into inner conductor. Some cables will have nylon wrapping beneath outer sheath to protect from Termites and steel tape armour for rodent protection. Metallic armour not only provide mechanical protection it can also offer EMC protection but dose not replace the need for screen but lines  less than 25kV can consider avoid screen under specific conditions.   1) Steel Tape Armour Steel Tape armour is sandwiched between water blocking tapes for DB cable. These are used for buried cables. According to American Railway Engineering and Maintenance of way Association (AREMA) states that tape armouring provide high degree of shielding protection than shield wires. 2) Steel Wire Armour Steel wire surround lead sheath for some cable design and are used for buried cable. This will surround the braided sheath and such sheath are used for high frequency emc protection 3) Corrugated armour Corrugated steel /copper surround the cable lengthwise beneath the outer sheath which is used for lines less than 25kv  .This is mainly used in Optical Fiber Cable for optimum flexibility and recommended to replace with Fibers Reinforced Plastic (FRP) for electrified territory more than 25kV due to chance for high induced voltage.                8.5.2 Types of Shield/Screens Screening /shielding is used for reducing the effect of electromagnetic interference (EMI) or electrical noise which can disrupt the transmission performance in some environments. This noise may be because of external interference from other electrical equipment or because of interference generated within the cable from adjacent pairs (cross talk).   1)  Aluminium /polyester tape with a tinned copper drain wire          DB 416.0115-Standard Quad Cable referenced in Figure 2 have aluminium foil with attached tin plated copper wire .   2)  Copper /polyester tape with a tinned copper drain wire   This solution can provide better screening effect compared to aluminium foil. 3) Bare copper braid This is good for electromagnetic interference when the cable is subject to movements   4) Tinned copper braid Good for  electromagnetic interference in presence of corrosive atmosphere or high temperature 8.6  Outer Jacket  In addition to insulating individual cores, the entire cable must be contained within a sheath for both mechanical strength and environmental protection. Cross Linked Polyethylene (High Density Polyethylene Otherwise known as HDPE) are the most widely used. Low Density Polyethylene-LDPE) are also used depends on area of usage. Some older cables used lead, but its expense and associated health risks have led to its disuse. The choice of sheath material should consider the environment in which the cable will be used. Factors such as moisture, exposure to light and heat, the presence of oils and solvents, presence of carbon/iron dust, Train washing plant solutions, temperature, water immersion (IPX7) /submersion (IPX8) and the required level of resistance. In nutshell outer jacket is one of the most important elements for mechanical protection from external damages such as chemical (oxidation acid, oil), Mechanical (Abrasion), Environmental (Heat, Sun exposure, moisture, water), Fire exposure etc. Thermoplastic or Thermoset polymers are widely used where Thermoset have excellent properties against threats.               8.6.1  Ingress Level- Mechanical Properties.   Mechanical shock severity shall be shared with the cable supplier whether its Low (Energy shock of 0.2 J, mainly for household installation hence not applicable) or Medium (Energy shock of 2J-standard industrial application) or high severity (Energy shock -5J) 8.6.2   Ingress Level- UV Resistance.                Designer shall share the UV intensity requirement to the cable supplier based on the regional severity and exposure levels whether its Low (AN1 – Intensity ≤500 W/m²) or Medium (<500 W/m² intensity ≤700 W/m²) or High (<700 W/m² intensity ≤1120 W/m²). Refer Rail Factor Article “Standards for Signalling Cables” for more details.  8.6.3   Ingress Level- Water 8.6.3.1    Water Environment 8.6.3.2  Water Penetration The factor defines the water penetration in cables and to prevent the entry and migration of moisture or water throughout the cable. Water ingress can happen through Radial due to sheath damage and in this case, water enters in the cable by permeation through protective layers or due to any mechanical damage. Once water enter the cable, it travels longitudinally through out of the cables core. Where as longitudinal penetration moisture or water enters inside cables core due to ineffective capping or poor cable joint /termination .Please note water proofing and water absorption tests are different .There are no specific test for longitudinal water penetration for power cables .Radial water penetration test shall only be applied .Separate water penetration barrier are applied below the armour (or metallic screen layer )  and along conductor .Refer cable construction above in Figure 2     8.6.3.3  Moisture Protection Resistance offered by the jacket and the additional chemical used are ensuring the protection. However, the material with highest degree of water resistance is often not flame resistant, hence a tradeoff must be made between these two contradictory requirements. Choice of sheath material, make use of chemical moisture barrier and water blocking tapes can protect the cables from moisture.          8.6.4  Flame & Fire   8.6.4.1   Low Smoke Zero Halogen (LSOH) This is the property of cable to emit very low smoke and zero halogen and ensuring low corrosivity and Toxicity. Even though normal PVC cable ensure better mechanical and electrical properties, its poor in fire retardancy, corrosivity and low smoke capability.   8.6.4.2   Smoke Density Smoke can prevent fire fighters’ visibility and evacuation, especially in tunnel, work areas, control room and public areas. 8.6.4.3    Flame Retardant Flame Retardant property is vital, during a fire flame spread shall be retarded to limit to a confined area thus eliminating fire propagation. 8.6.4.4    Fire Retardant Property which when ignited do not produce flammable volatile products in required amount to give rise to a secondary outbreak of fire. 8.6.4.5    Fire Resistant Fire resistant cables are designed to maintain circuit integrity of emergency services during fire. Please note that Fire resistant cables are super expensive and normally considered for very vital cables (Eg; Fire cabinet ,depend  on contractual requirement .Please note that Fire Resistant and fire retardant are different property and fire resistant is more stringent requirement. The individual conductors are wrapped with a layer of fire resisting mica/glass tape which prevents phase to phase and phase to earth contact even after the insulation has been burnt away. The fire-resistant cables exhibit same performance even under fire with water spray or mechanical shock situation.               8.6.5    Pest Resistant                Depends on the intended area of the project ,there could be various threats  such as  ants, termite ,rodents , squirrels ,wood peckers ,other birds ,beetle and larva where cable contact with any plants to mention some .Various chemical compounds added on to the sheath ,depends on pest chemical and armours are protecting the cable .It may not be practical to have armoured cable for indoor application due to flexibility issue and outdoor environment have more threats . 9.   ELECTRICAL PROPERTIES SIGNALLING CABLES 9.1  Voltage Rating of Cable Signalling control cables are normally rated for 600v/1000V. Voltage range classification for LV, HV, AC & DC according to IEC 60038 are as shown in Table 3 Maximum for High Voltage for IEEE is 35kV and in some countries its 45kV, which is country specific. Refer Table 4 for maximum permitted voltage Vs Rated voltage.  9 .2   Resistance of Cable This is the resistance of wire which increases with distance and normally included in the cable data sheet from the supplier. Its measured Ω/kM @ 50Hz (or 60Hz) and 20°C. This is the main parameter to calculate the voltage drop of cable. Voltage received at the end gear shall not be less than 10% of the source voltage. This means when you feed 130V from the SER, signal at the track side should at least get 117V. Cable conductor size shall be selected based on voltage drop calculation and shall cross check with field gear data sheet that the 10% voltage drop allowed will still fall in the minimum required voltage Important Note: Signal Engineer shall ensure that the resistance value (Ω/kM) provided by the supplier in the data sheet is loop resistance or wire resistance. Loop resistance means it’s the value for two conductors. While calculating voltage drop, number of loops used for the respective circuit and its distance shall be used. 9.3   Reactance of Cable This is defined in Ω/kM @50Hz (or 60Hz). This is important parameter for MV cables which need to be asked from the supplier but for LV, designer can define the allowed limit for LV 9.4  Capacitance of Cable Measured in µF /KM which is mandatory parameter for MV cable and shall be requested from supplier. As mentioned above Quad formation have less than 40µF /KM. Lower the capacitance better the cable property. 9.5    Maximum Short Circuit Current (Conductor and Screen)   Maxum short circuit current in kA for conductor and screens for 1.0 seconds and 0.5 seconds respectively shall be requested and obtained from supplier. 10 CABLE TESTING It is not the purpose of this article to give detailed instructions on the procedures for testing and maintenance of different types of cable. However, the general principles of cable testing are described here. In general, whenever a cable is installed, repaired, re-terminated or jointed and at regular intervals during the life of the cable, tests must be made to ensure that: - a)  Each core is continuous and of the correct resistance. A rise in the resistance of a core could indicate a potential fault. b) Each core is insulated from all other cores. It is normal for the insulation resistance to fall slightly during the life of a cable. Serious deterioration must, however, be detected before it causes any safety hazard. c) Each core must be adequately insulated from earth. Unwanted connections to earth are a potential danger to all signalling circuits and must be avoided. Where the cable has a metallic sheath, the insulation tests must include the sheath. Where the sheath is earthed and/or bonded for reasons of safety or noise immunity, the continuity of the sheath is also important. The continuity tests may be made using a suitable digital or analogue multi-meter set up to measure resistance. All tests will require the cooperation of persons at each end of the cable. A telephone circuit between the ends (using the cable to be tested if convenient) is essential to carry out an efficient test. The simplest method is to put a loop between one conductor and each other conductor in turn at one end of the cable. The loop resistance is measured at the other end using the meter. Any variation between individual readings (and changes since the previous test) should be investigated and resolved before the cable enters (or re-enters) service. Insulation and earth tests should use a suitably rated insulation tester (1000-volt Megger or similar for signalling cables). Tests should be performed between each core and each other core in turn. The acceptable value of resistance for a cable will depend on the circuits connected through it. However, as a general guide, a new signalling cable should give readings better than 10MΩ (when terminated). Readings less than 1MΩ could potentially be dangerous and require urgent investigation. The earth test may initially be carried out between earth and all cores connected in parallel. Only if this test is unsatisfactory need individual cores be tested to earth. Although a new cable is always completely tested before being brought into use, a complete test of a working cable is not always practical without serious disruption. In this case, routine tests are often carried out on a sample of cable cores (spare cores if available). Previous readings should be retained for comparison. 11.  DATA CABLES Ethernet cables falls under this category. They are classified into different category Cat 1 to Cat 9, whereas Cat 1-4 are not suitable for modern day rail application and above Cat7 is not yet came into application while preparing the article. Refer Table 4 for category classification. Data cables with twisted pairs have different construction depends on the purpose, cable shall be selected. Refer Table 6 for various construction. 12. Fiber Cables Although many signalling applications must use metallic cables, the availability and cost of fiber optic cables is rapidly improving. Instead of electrical signals, they transmit information by passing light signals along the length of a glass fiber. Internal reflection contains the light signal within the fiber. Although not specifically employed in conventional signalling systems, fiber optic technology has the following advantages and necessary for modern communication-based train control system: - a)  An extremely high capacity and bandwidth. b) Immunity from all types of electrical It is therefore of great use for communications purposes on electrified lines. Conventional jointing techniques are not applicable to glass fiber cables. Instead, the two ends must be cut squarely, butted up to each other and fused together by the application of heat. This is a very precise operation as any irregularities in the fiber will cause attenuation of the signal. Much of the work of jointing fiber cables can now be done automatically by sophisticated (and usually very expensive) fusion splicers. The action of cutting the two ends squarely, aligning them for a parallel joint and fusing for the correct period of time is largely automatic. Even with the high degree of automation, fusion splicing is not always 100% satisfactory each time. It is therefore usual to provide additional spare fiber at the joint. This must be accommodated within the joint closure. Category cables have limitation to transfer data more than 100meter, Fiber has significance in this case. There are two types of fibers: Single Mode: Long Distance Application Multi-Mode: Short Distance Application Single mode Fiber must be complied to G652-D type as per ITU-T standard and multimode with IEC 60793-2-10  There are two types of construction Loose Tubes used in cable concrete trough, direct buried and other harsh environment Micro Tubes for less harsh environment The END  NOTE :- Please comment if you wish to include Cable Voltage Drop Calculation , Stanadard conductor sizes and a sample cable plan 

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Deepu Dharmarajan -
Posted 2 years ago

CH12B | Standards for Signalling Cables

Signalling

Railway Signalling, Communication and Power distribution for signalling equipment falls under Signalling Cables  category. Signalling Cables are categorized as high voltage, low voltage ,extra low voltage and fibre cables. According to IEEE ,high voltage cables are cables handling voltages greater than 1kV up to 35kV for AC Vrms and 1.5kV to 50kV for DC respectively .There are difference in this range from country to country  and can go up to 50kVrms . Low voltage cables carry voltage between 50V to 1kV for AC Vrms and 120V to 1.5kV for DC and extra low voltage cables carry voltages less than 50v  for AC Vrms  and 120V  for DC . Note!: Standards and requirements vary from country to country and user of this article shall check with the operator for the standards with in the country of application. Below table list the standards used in major railway countries and alternate standards may be proposed where no standard exist for certain requirement.                                 List of Standards and Application  Below are a list of  requirements , standards  along with title for various cable requirements .Requirements are classified as Mechanical and Electrical . 1.1. Mechanical Properties  Requirements for the protection of the cables against potential threats  1.1.1. Water Protection Stringent water protection requirements are applied based on the intendent environment and cables properties are defined from negligible water threat to immersion or complete submersion. Water penetration can be Radial due to sheath damage and water travels longitudinally. Water blocking tapes are considered as  moisture protection.Below are various standards which are applied depend on intended application.                         1.1.2. LS0H (Low Smoke, Zero Halogen) Especially tunnel and enclosed environment its important to ensure cable properties are free from emitting hazardous gas and smoke during fire.                                         1.1.3. Fire& Flame  Retardant ,Fire& Flame  Resistant Please note that retardant and resistant have different meaning ,Fire /Flame resistant is more stringent and cable will be expensive .Fire/Flame retardant cables resist the spread of fire into a new area, whereas fire-resistive cables maintain circuit integrity and continue to work for a specific time under defined conditions. Resistant in this context is defined as a material that is inherently resistant to catching fire (self-extinguishing) and does not melt or drip when exposed directly to extreme heat. Retardant is defined as a material that has been chemically treated to self-extinguish.                                                           1.1.4. Ultra Violet Protection Cable which are directly exposed to sunlight shall be resistant to  Ultra Violet  radiation. Test shall be conducted as per requirement on the intended terrain of cable application  for Low(AN1) ,Medium(An2) or High(AN3)                  1.1.5 Abrasion & Crush  Abrasion and crush load resistance test to be performed to ensure the cable can have longer life span for the signalling system life.           1.1.6 Longer Service Life Crush  Thermal aging tests are performed as defined in EN 60811-401 to ensure cables can long last at least life span of the signalling system               1.2. Electrical Properties  Below list cover some of the standards for electrical properties of the cable    1.2.1. Ohmical Resistance              1.2.2. Mutual Capacitance                1.2.3. Insulation Resistance               1.2.4. Di-Electric Strength               1.2.5. Conductor       1.3. Australian Standards

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