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Question and Answer Session from the AGRRI Seminar, 25/11/2003, Network Rail, London

If you're looking to attend a workshop on the New EMC Directive and Technical Documentation for the Railway Industry, we're running one in London on Wednesday, 4th June 2008 at the IET's Savoy Place.

The Advisory Group on Rail Research and Innovation (AGRRI) ran a seminar, sponsored and organised by Network Rail, on ‘EMC in Railways: Who and How’ The seminar was a unique opportunity to learn from leading industry experts on research and management in EMC and to influence how the industry's obligations will be discharged. It also introduced Network Rail's emerging thinking on EMC policy.

There will be a continuation of this discussion at EMC York 2004, in a dedicated ‘railways’ conference stream.

The question and answer session from the open forum has been transcribed for your reference.

Q: How "unprotected" actually is the RF Spectrum? Do we understand sufficiently, how for example the capture effect mitigates against random noise transgressing a channel? - Clive Avery, AEAT
A: The Radio Spectrum is a resource where frequency allocations are managed at International level by the ITU. The ITU allocations are then implemented at National level. The Radio Spectrum is protected from interference by EMC Standards which set limits for unwanted radiated emissions. Part of the lack of acceptance by the Radio community of EN50121-2 is that the limits set are significantly higher than those set by accepted EMC standards - 50-60dB more! The Radiocommunications Agency commissioned York EMC Services Ltd to investigate this. The results of the first contract appear on the YES and RA [now OFCOM] websites, the latest measurement results were presented as part of the AGRRI seminar by Andy Rowell. The key issue is that the limits in EN50121-2 are set at a level that can be measured at the trackside using conventional antenna and spectrum analyser system with the analyser using a peak detector - hence recording transient and continuous noise. The new measurement system described allows the transient and continuous noise to be identified separately and therefore the EN50121 limits can be adjusted to reflect the continuous noise and therefore the continuous threat to the radio spectrum - Chris Marshman, York EMC Services Ltd
Q: Why is the standard (GE/RT8015) limited to 2 GHz, when 3G coms & Bluetooth use frequencies in the range of 2.4GHz? - Dennis Stanley, Bombardier Transportation
A: GE/RT8015 covers a similar upper limit to the range as that covered in EN50121. However you make a good point regarding newer technology. Perhaps both sets of standards should be modified accordingly - Jeff Allan, RSSB
Q: No mention so far of EN50155 - why has it not been included within the EMC compliance process? - Tony Barwell, TUV
A: EN50155 was one of the early standards for commonality of sourcing for railway equipment in general. It covers environmental in addition to EMC issues; those tests and limits, which fall within the preview of EN50121 are harmonised with or similar to EN50121. It also includes requirements for conducted interference emission and immunity outside of the frequency limits of EN50121, and limits for tolerance of supply voltage variation. It tends to be overshadowed by EN50121 as it does not carry the weight of an EU Directive as does EN50121, but remains a valid and useful standard - Clive Avery, AEAT
A. EN50121 actually calls up EN50155. It should be noted that the requirements of EN50155 in terms of Surge are less onerous than EN61000-4-5 and much less onerous than the old RIA 12. - Chris Marshman, York EMC Services Ltd
Q: In relation to plant & equipment using for eg 12/24vdc: Can the production of the Technical file/safety case be made easier by documenting some evidence on what criteria systems/components would give risk of emitting/receiving unacceptable levels of EMC? - John Ockenden, Carilion Rail
A: When compiling a TCF, the EMC data for the systems/components being integrated into the final delivered system, should be obtained from the manufacturer/supplier. This evidence is part of mitigating the risk and demonstrating that the final system will be compliant, this will however depend on the integration process and verification (EMC testing at system level) - Chris Marshman, York EMC Services Ltd
Q: Is there an agreed industry wide approach to the EMC Directive with respect to rolling stock?
Example: new telecoms equipment to be fitted to rolling stock made up of CE marked units, is this a system or installation? is a TCF required? for system or installation? - Justin Caton, Development Engineer, HSBC Rail
A: Let us consider the example. New telecoms equipment should be CE marked in relation to the R&TTE Directive. This equipment is being procured for existing rolling stock. Considerations are that conformance to the R&TTED does not necessarily mean that the equipment is robust from an EMC point of view in the rolling stock environment, also how will the telecoms equipment affect the EMC characteristics of the rolling stock and hence affect its Safety Case? The telecoms apparatus manufacturer or the system integrator should ensure that the apparatus has adequate immunity to operate satisfactorily in the rolling stock environment. Assuming the out of band emissions from the telecoms equipment meets appropriate limits and that the equipment is installed using good practice, then the rolling stock emissions are unlikely to be affected except at the transmission frequencies/bands of the apparatus. The compatibility of such telecoms with the railway network should have been undertaken prior to consideration of fitting the apparatus. In the case of non-telecoms equipment eg an OTMR then the OTMR will have to comply with the EMC Directive. It will be necessary to demonstrate that the OTMR is suitable for use in rolling stock. An approach here would be to test to EN50121-3-2 and present the results in a TCF, the OTMR can then be CE marked - the TCF should provide generic installation guidance to enable the system integrator to install the equipment. When installed it may be necessary to verify that the emission characteristics of the rolling stock are unaffected and therefore that the Safety Case is unaffected. This may be regarded as the minimum approach for retrofitted equipment. An alternative valid view is that it is the installed OTMR system that is being supplied and that this should conform with the EMCD. This will require a TCF for the installed system and will be generic for a number of vehicle fitments with verification measurements performed on a representative example of rolling stock fitted with the OTMR - Chris Marshman, York EMC Services Ltd
Q: Does the directive differentiate between "repair" and "re-conditioning" equipment built before the directive came into force? What about "re-conditioning" equipment built before the directive came into force? Does this then require a TCF? - Simon Jarrett, Angel Trains
A: The EMCD is not retrospective and so does not apply to equipment built before 01/01/1996. It does not cover 'spares' and only applies when equipment is 'first placed on the market or taken into service'. So, repairs that restore equipment to its original specification are outside the scope of the EMCD. Reconditioning is treated by the EMCD as manufacture. Where reconditioning is entirely mechanical eg new seats etc and the electrical systems are restored to the original specification, then reasonably this may be considered in the same way as a repair, however when a major rebuild takes place then this is the same as for new manufacture eg Brush Class 57. Where reconditioning is accompanied by partial integration of new electrical/electronics systems then these should be considered in the same way as for the OTMR example given above, ie as a minimum the equipment being installed should be CE marked as fit for the intended operating environment eg on-board rolling stock - Chris Marshman, York EMC Services Ltd
Q: In the light of the evidence shown in Andrew Rowell's presentation, showing that RF emissions from the railway are shaped both by the train and by the configuration of the traction supply system - and will also be influenced by the number of trains in the area - how is responsibility for emissions from the railway to the outside world, in accordance with the requirements of the EMC directive, determined - does the infrastructure controller have to take ultimate responsibility for the total emissions, as he has control of:
  a) design of infrastructure, including traction supply system.
  b) number of trains he allows to operate in an area.
If so, he must also be responsible for emission characteristics of the trains he allows onto his network - David Bulgin, RSSB
A: The EMCD is intended to cover the supply of electrical/electronics apparatus into the European market place. It is primarily targeted at manufacturers and it is the responsibility of manufacturers to demonstrate conformance with the essential protection requirements. So, for new rolling stock it is clearly the manufacturer's responsibility to demonstrate conformance and that it will conform when used in its intended operating environment. It is the user's responsibility to ensure that he only takes into service compliant equipment, in the case of rolling stock the TOC. There is therefore some responsibility placed on the ROSCO to ensure that compliant equipment is procured, depending on the contractual arrangements between TOC, ROSCO and manufacturer. In order for the manufacturer to deliver compliant equipment he needs to demonstrate that the protection requirements are met for the environment, therefore the manufacturer needs to take account of the infrastructure. The threats posed by the infrastructure to the rolling stock and from the rolling stock to the infrastructure need to be identified and mitigated against. This implies that the EMC details of the infrastructure are available to the manufacturer. If not, the manufacturer can only rely on published agreed standards ie EN50121-3-1. The threat to the outside world may however be minimised by the number of trains operating in the area and this would be a legitimate limitation on use specified within the TCF for the rolling stock. So, the responsibility for new rolling stock does rest with the manufacturer, the law however requires him to be duly diligent and this may be limited by the availability of the EMC characteristics of the infrastructure. The infrastructure controller does have responsibility for the emissions to the outside world when he is responsible for making changes to the infrastructure and in this instance the rolling stock is part of his environment with limitations which must be taken account of when planning the changes. Such changes should come under Network Rail’s EMC policy and the WCRM EMC Assurance Guide - Chris Marshman, York EMC Services Ltd
Q: EN50121 Part 4 should have become a free-standing harmonised standard several years ago. Who is responsible for failing to get this done? - Donald Armstrong, Atkins Rail
A: This would be extremely helpful to many manufacturers. I don’t know who is responsible for failing to get this done. I believe EN50121 is being viewed as a package and therefore all of it needs to be adopted not just a part - Chris Marshman, York EMC Services Ltd
Q: The term 'excluded installation' as specified by UK SI 2372, can the panel clarify that fixed installations are only excluded from the need to CE Mark and NOT excluded from the need to meet the essential protection requirements? - David Atkey, ERA Technology
A: This is correct. The EMCD applies to installations, what is excluded is the need to CE mark the installation. The installation should still meet the protection requirements - Chris Marshman, York EMC Services Ltd
Q: As a supplier of IT and telecommunications equipment not specifically designed for railway use, do the panel conclude that a TCF is required when the directives specifically exclude fixed installations, and the new directives go to great lengths to clarify this position? - Mark Brooke, Marconi
A: The old chestnut! COTS equipment when integrated into equipment for railway use should conform with the appropriate directives for the intended operating environment ie a railway. This will require the use of TCFs in many instances, for example, when equipment is within 3m of the rails or when EN50121 is being used to demonstrate conformance. As stated in the previous question the so-called excluded installation is only excluded from the conformity assessment procedure. The new EMCD doesn’t exclude fixed installations either it only excludes them from being CE marked, it does however require that the installer/user of such a fixed installation is able to demonstrate that the equipment meets the protection requirements. As the new EMCD is not likely to be effective until 2007-8, Marconi is required in the meantime to comply with the existing EMCD and where COTS equipment is being integrated it is subject to further manufacture and is therefore within the conformity assessment regime ie it must be CE marked - Chris Marshman, York EMC Services Ltd
Q: How does NR audit/police EMC compliance requirements with relation to procurement of equipment installed on NR infrastructure? - Dominic Kelsey, Rail Link Enterprise
A: Evidence for the achieved EMC for new installations, upgrades and modifications is provided as part of their acceptance case. Currently, NR has no coherent policy of acceptance of different infrastructure products on the network. Approvals of signalling equipment has been following the process in NR Code of Practice RT/E/S10071 'Approval of signalling equipment' Issue 1 of December 1997 which requires that EMC with existing railway systems and equipment is achieved. Often, functional testing is taken as proof that EMC has been achieved – Maya Petkova, Network Rail
Q: As railway infrastructures are fixed, have known characteristics, can be tested in labs and protected by filters and screening why is there not more emphasis on reducing susceptibility limits, rather than worrying about train emissions. Every time a new train is built/designed it will need extensive expensive trialling. A moving train EMC profile will deteriorate far quicker than static infrastructure - Geoff Eggrison, Marconi
A: New technology being introduced is generally more immune to EM interference. In addition, all signalling product upgrades are tested for immunity as per EN50121, which has more onerous requirements. There is still a strongly defined need for a thorough compatibility assessment with trains and other systems, which is performed in accordance with the principles set out by EN50238. Recent projects that applied its principles include SSI and compatibility with Class 390 train that was accepted without a clearly defined safety margin but on the basis of the results of monitoring and the assertion of the robust design of SSI. It is important to remember that any EMC argument is time limited and only valid at the time of acceptance and the EM environment is evolving all the time - Maya Petkova, Network Rail
Q: To what extent should a Contractor show due diligence for EMC compliance, including satisfying the safety case, when designing, assembling, installing on the NR infrastructure various sub-systems interlinked in modular format? The modules, in turn, contain items of equipment and components in their own right - Raymond J Leach, Network Rail
A: The top level requirements for EMC in terms of safety and corresponding safety cases is contained within GE/RT8015 - Maya Petkova, Network Rail
A: The WCRM EMC Assurance Guide provides the guidance needed - Chris Marshman, York EMC Services Ltd
Q: What is the responsibility of NR in providing suitable guidance to contractors where they are contracted to introduce new sub-systems on to the infrastructure? - Raymond J Leach, Network Rail
A: By adopting the EMC Policy as presented at the EMC Seminar, NR should make sure that EMC requirements in accordance with GE/RT8015 are part of the procurement contract. Evidence that analyses to the depth required by GE/RT8015 should be presented in the safety cases. This may be test results, or results from modelling, as appropriate (e.g. regarding safety targets requirements results from modelling can be confirmed over time in operation, as accumulated) - Maya Petkova, Network Rail
A: The WCRM EMC Assurance Guide provides the guidance needed here - Chris Marshman, York EMC Services Ltd
Q: Would a Competent Body be required to assess the evidence of EMC if the standards and TCF route is followed, and if so, would this be a joint responsibility between NR and subcontractor? - Raymond J Leach, Network Rail
A: NR as infrastructure controller is ultimately responsible for conformity to the protection requirements of the EMC Directive. The TCF route should be followed to demonstrate compliance with EN50121 (the harmonised European standard for railways) and the assessment of Competent Body sought since EN50121 is not in the OJEC. It is important that this responsibility is assigned to the responsible contractor during design and installation stage and all relevant measures adequately recorded in the EMC Project File. By accepting the EMC Project File, NR effectively satisfies the protection requirements and agrees that the applied EMC standard is appropriate, i.e. demonstrates due diligence has been applied as far as this part of the lifecycle process is concerned - Maya Petkova, Network Rail
A: The WCRM EMC Assurance Guide provides the guidance needed here - Chris Marshman, York EMC Services Ltd
Q: EMC Directive states that fixed installations are excluded (Maya Petkova morning presentation). Traction sub-stations are inherently fixed in nature (apart from circuit breaker operations), so would these types of sub-systems being introduced to the NR infrastructure be exempt? - Raymond J Leach, Network Rail
A: The equipment/systems within the sub-station should all comply with the EMCD. The sub-station is an excluded installation, again excluded from the CE marking regime but not excluded from the protection requirements. Sub-stations are addressed by the WCRM EMC Assurance Guide, where it is expected that a Technical File (equivalent of a TCF but not a legal requirement) will be prepared to cover the sub-station. This file should be assessed by a Competent Body - again this is not a legal requirement - Chris Marshman, York EMC Services Ltd
Q: The application of the maximum allowable train emissions of more than 50% of the normal level will be generally impossible to apply. In most cases a single fault condition will have a much greater effect on the allowable level than 50%, for example rail breaks in track circuits, or cable faults on lineside systems. The problem then remains - what is the acceptable level of fault analysis that needs to be carried out? That will be the dominating factor. Any comment? - Adrian Hines, A Hines Engineering Ltd
A: There is a similar problem with emissions from trains. Train builders need to consider faults, which could increase emissions. Generally, emissions are held to a tight level compared with normal values by means of fault analysis and management of those faults. The same process is being sought from infrastructure designers and maintainers. Therefore the question is: can something be done to control these faults? If not, the standard allows agreement between the infrastructure controller and all train operators using that section of track to a different agreed allowable level e.g. 10%. In this way at least all parties would agree that nothing could be done to reach an allowable level of 50% or better - Jeff Allan, RSSB
Q: Why is the margin between minimum per train infrastructure susceptibility (normal conditions) and maximum allowable per train emissions set at 50 % (at best), ie 6dB total (at best) in fig. 1 of GE/RT8015? - Dick Wall, Alstom TIS
A: I would not argue strongly if someone stated it should be 30% or 70%. What is clear is that it should not be 90% - there is too little allowance for faults and degradations nor should it be 10% - in this case the system is too sensitive and putting too much burden on train operators having to tightly control emissions, while not providing infrastructure which is properly engineered to counter emission threats. For older infrastructure (the majority) there is always the option of the infrastructure controller agreeing a different level to 50% with all train operators using that section of track - Jeff Allan, RSSB
Q: The 25 kV overhead is resonant at many frequencies. For example, 3.8MHz at one site. Does the approach presented by Andy Rowell find these? What is the bandwidth for the 360MHz timeplot? - Donald Armstrong, Atkins
A: The new measurement system does show the effect of resonances quite clearly. In the example presented showing a Class 91 on the ECML, it is observed that the the maximum emissions occur some time before the train passes the antenna and again that the emissions rise as the train moves further away. What we don't yet know is whether the levels measured are independent of antenna position. This work is currently drawing to a close and a new sponsor is sought to continue the research so that we can consider further areas such as resonance - Chris Marshman, York EMC Services Ltd

Last Updated: 2008-Apr-18

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