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IEE EMC and Railway Professional Networks Seminar

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‘EMC Assurance in a Railway environment’ — 09 September 2003

The EMC and Railway Professional Networks ran a very successful event on 09 September, which established through the presentations and discussions the current electromagnetic compatibility (EMC) issues faced by the Railway industry in the UK. Key issues that arose can be summarised as:

The event was attended by participants who represented the whole of the Railway Industry: Network Rail, LUL (Infracos), Manufacturers, Power Companies, ROSCOs, TOCs, VABs, NOBOs, HSE, RSSB, ORR, Consultancies and EMC test laboratories; and was sponsored by the Radiocommunications Agency. A small exhibition accompanied the event; exhibitors were: Deltron, ITI, EMC Hire Ltd and York EMC Services Ltd.

Chris Marshman, York EMC Services Ltd, chaired the event, the speakers were:

Peter Kerry gave the keynote address, and stressed the need for the Railway not to see itself in isolation but as part of the larger UK electromagnetic environment. Peter referred to advances in technology and the resulting changes producing an ever more hostile EM environment. Hence there are new threats to the railway posed by the introduction of new mobile telecommunications and Wi-Fi systems and the ever increasing IT clock frequencies and resulting harmonics. The Railway also poses a threat to the new DAB services being introduced. Therefore, Peter stressed the need for greater cooperation and participation in standards organisations since the railway industry is more fragmented and more sophisticated technology is being introduced in the world beyond the railway but is brought onto the railway by its customers.

Maya Petkova explained the relationship between Railway Safety Cases and the proposed changes to the safety case process and the impact of these on EMC and safety. Maya established the difference between conformance with the EMC Regulations, which can be seen as the minimum requirement and the requirements for safety. She described the requirements of route acceptance safety [GE/RT8270] with the EMC assessment to follow the process laid down in GE/RT8015. This requires access to the Industry Data Initiative (IDI) database and it was announced that there is be a second phase of the IDI addressing the current lack of data. Network Rail’s expectations are that in future all project contractors will have an EMC Project File that will demonstrate conformance with both the safety and regulatory requirements. Maya also presented the concept of adding a 10m buffer zone to the EN50121-2 defined railway boundary, bridging the gap to the ‘residential, commercial and light industrial’ environment. Finally Maya addressed the important issue of maintenance; once a maintenance regime is established then NR aims to establish audit procedures of EMC relevant records.

Chris Marshman explained the legal requirements for conformance with the EMC Directive, set out the essential protection requirements and the routes to conformance with these. European Harmonised EMC Standards were described and the status of the EN50121-x series of EMC standards for railway applications was discussed. Because these have not been published in the OJEC, test results to these standards must be incorporated within a Technical Construction File in order to meet the legal conformance requirements. The need for EMC project management from concept was presented along with case studies for an EMU and the Class 57 ‘reconditioned’ locomotives.

Jeff Allan presented the requirements for EMC and safety as set out in GE/RT8015. The key features of the standard are: a mandated process of characterisation of all infrastructure (IDI); an approach to determining acceptable train emission levels based on agreeing a defined level of infrastructure degradation/fault tolerance; greater emphasis on the need for new infrastructure to be designed to minimise or eliminate effects of train emissions on safety; clearly defined roles and responsibilities for the infrastructure controller and the train operators; alignment with the relevant European Standards — EN50121-x and EN50238; an equitable sharing of risk between the infrastructure controller and train operators. GE/RT8015 builds on the route acceptance process and provides a framework for the effective management of EMC and control of the associated risks to safe operation of the railway.

Ade Ogunsola described the integration of EMC engineering within the scope of a system engineering framework, enabling the management of EMC throughout the lifecycle of the system right from requirement definition to commissioning and maintenance. It was highlighted that attention must be paid to system interfaces that can act as propagation paths for interference. It was identified that: the safety assurance process requires support from specialist EMC expertise during the hazard identification (HAZID) and risk assessment process; the EMC assurance process requires an understanding of the ‘Safety Concept’, applying safety engineering techniques; EMC Safety requires a detailed assessment of the EMI induced failures and their impact on the safety status of the apparatus; and that Fault tree analysis can be used to define the EMI induced failures that may result in an unsafe state.

Dave Bradley described: the ‘historic’ measures taken to mitigate EMI effects on railway equipment; the more subtle EMI problems that are becoming apparent; and the application of GE/RT8015. Dave described both dc and ac electrification characteristics and their effect on track circuits; in principle immunisation being achieved by using ac track circuits on dc systems and dc track circuits on ac systems. Particular mitigation measures described included the use of Booster transformers on ac OLE systems that effectively reduce loop areas and interference to telecommunication systems. Particular EMI problems associated with modern traction and electrification systems were described and the resulting actions, these included: suppression-at-source (Boosters); monitoring of traction equipment (ICMUs); design of traction equipment to avoid critical harmonics (Thyristor/IGBT ‘firing’ strategies); replacement of sensitive signalling equipment; immunisation of signalling equipment; and additional maintenance of critical circuits. Complex EMI effects were described including resonance effects in the OLE mitigated by resonance dampers. Considering GE/RT8015, two practical mitigation measures for the infrastructure were presented; additional cross bonding (up to 4x), as this is simple to design and install and reduces risk to ALARP; for line-side circuits improvement in earth fault detection by more frequent manual testing or installation of monitoring equipment.

Prof Andy Marvin described the results of research carried out by York EMC Services Ltd and the University of York, sponsored by the RA, into radiated emission measurement techniques for moving rolling stock. Earlier work for the RA had clearly demonstrated that EN50121-2 gave inadequate protection to broadcast and radio services. However the limits set in the standard were based on line-side observation using receivers employing peak detectors. The novel measurement technique developed uses multiple antennas, an RF signal splitter and multiple receivers, controlled by computer. Time and frequency domain techniques are used to separate the transient noise due to pantograph arcing from the continuous emissions from the traction package. Results were demonstrated. It is intended that the results from this ongoing research will be fed into the standards bodies ultimately enabling a reissue of EN50121-2 and 3-1. York EMC Services have been short listed for the National Measurement Awards for this measurement system.

The final paper of the seminar was presented by Andy Bourne and described the experiences of managing EMC on the LUL system. The specification of comprehensive contractual requirements is seen as fundamental to the successful achievement of EMC. Experience has shown that reliance on meeting only regulatory requirements and standards leads to a wide range in the quality of assurance evidence. LUL has derived its own EMC standard E1027 and manual of best practice M1027. These are based on the EN50121-x series of standards but expand on them to cover the identified gaps and additional requirements. Particularly Andy pointed out that reliance cannot be placed solely on a manufacturer’s Declaration of Conformity. EMC Management of projects was identified as crucial to the achievement of EMC, starting with the ITT, the need for an EMC Control Plan and the requirement for a project EMC coordinator. EMC testing was discussed and whilst on-site emission testing was recognised as validating the design and integration process it is not seen as a substitute for rigorous testing at sub-system level at a UKAS accredited testing laboratory. Current issues highlighted were: the use of mobile phones and the threat to COTS equipment with immunity levels of 3V/m; radio based communications systems; ‘legacy systems’ with unknown EMC characteristics.

The seminar concluded with a lively Q and A session. The issues arising from this seminar will be carried forward and addressed at the AGRRI seminar ‘EMC on Railways - Who and How?’ on 25 November 2003 at 40 Melton Street. At this seminar Maya Petkova will present Nework Rail’s proposed new EMC Policy. For those in the industry requiring an introduction to EMC in Railways, York EMC Services Ltd’s popular short course is a useful primer. You can check when it next runs.

Chris Marshman, 16 September 2003

Last Updated: 2006-Apr-02