01.01.07
EMC in railways – safety and the legal requirements
Electromagnetic compatibility (EMC) between electrical and electronic systems is an essential requirement for the reliable and safe operation of equipment. It is all too apparent that traction power equipment may interfere with signalling systems with potentially dire consequences. So EMC is one of the requirements to be included in a safety case for the introduction of new rolling stock, locomotives or track maintenance vehicles.
Today we have a situation where the rail is the guidance system, the return power conductor in ac or dc railway electrification schemes and is also used as a conductor of low power level coded signals for signalling.
The interference problem is compounded by the widespread use of inverter driven ac traction motor drives. Further, the railway constrains telecoms and signalling cables to run parallel to the traction power supply system, allowing coupling of disturbances onto these cables. This can cause interference and induce high touch voltages.
The new EMC directive (2004/108/EC) and the implementing UK regulations (SI 2006 no. 3418), will further impact upon the railway from 20 July 2007. The railway is a ‘fixed installation’ under these regulations and the ‘good [EMC] engineering practices’ used for the installation of equipment must be documented and held by a ‘responsible person’ and be available to the enforcement authorities whilst the fixed installation remains in operation. The definition of ‘responsible person’ will affect contractors and infrastructure controllers and will require clarification in contracts for the handover of responsibility and of documentation.
The new directive also affects equipment manufacturers. All equipment carrying the CE marking will require ‘technical documentation’ to be prepared, equivalent to the old TCF. The manufacturer can choose for this to be assessed by a notified body.
It is therefore essential to manage EMC to meet the technical, safety and legal requirements from project concept by implementing an EMC management plan. EMC testing must be carried out subsequently to verify that EMC has been achieved. York EMC Services has considerable experience of railway EMC problems and issues, is a competent/notified body and can assist all parties in the rail industry.
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