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Guide · Rail & Metro · Built in India
EN 50121 is the European series of standards for electromagnetic compatibility (EMC) in railway applications. It sets emission limits and immunity test requirements so that rolling stock, onboard apparatus, signalling and telecommunications equipment and fixed power installations can work together without disturbing each other or the world outside the railway. IEC 62236 is the closely aligned international series.
The short answer
EN 50121 (Railway applications, Electromagnetic compatibility) is published by CENELEC in parts. Part 1 sets general requirements, including the performance criteria used to judge immunity tests. Part 2 limits emissions from the whole railway system to the outside world. Part 3-1 covers trains and complete vehicles, and Part 3-2 covers electrical and electronic apparatus installed on rolling stock. Part 4 covers emission and immunity of signalling and telecommunications apparatus, and Part 5 covers fixed power supply installations and apparatus. The current parts are the 2016 and 2017 editions, with Parts 3-1, 3-2, 4 and 5 amended by A1:2019, and a revision of the series is under way.
Why it matters
A railway is a dense electromagnetic environment: traction power, converters, radio systems and long cable runs sit close to sensitive electronics. Onboard passenger information displays, CCTV cameras and recorders, and remote monitoring gateways must not disturb train control or communication systems, and must keep working when exposed to transients, surges, radio-frequency fields and electrostatic discharge. For apparatus fitted to rolling stock, EN 50121-3-2 is the usual EMC reference, and EN 50155 refers to it for EMC testing. At the trackside and in stations, EN 50121-4 covers signalling and telecommunications apparatus that is vital to train operation or installed within defined distances of the track; other apparatus is pointed to the generic immunity standard EN 61000-6-2.
Key requirements
A summary of what the rolling-stock apparatus part asks for. Always check the exact parts, editions and amendments named in your tender.
Conducted emissions are limited on power and battery ports, and radiated emissions from the enclosure follow the industrial limits of EN 61000-6-4, measured at 10 m, so that onboard apparatus does not disturb other systems. The 2016 edition extended the radiated emission requirement into the 1 GHz to 6 GHz range.
Immunity is tested port by port using the EN 61000-4 basic test methods: radiated and conducted radio-frequency disturbance, fast transients, surges and electrostatic discharge. For example, the radiated field level is 20 V/m from 80 MHz to 1 GHz for equipment in passenger areas, the driver's cab or mounted outside the vehicle, with lower levels in higher bands.
The manufacturer provides a functional description and declares how the apparatus must behave, using the criteria in EN 50121-1: A, it keeps operating as intended during and after the test; B, performance may degrade during the test but recovers, with no change of operating state or stored data; C, temporary loss of function is allowed if it self-recovers or can be restored by the controls.
Tests depend on the apparatus, its ports and its operating conditions, so the test plan and report should list every port and the configuration tested, together with the performance criteria. When apparatus is installed in new or existing rolling stock, EMC is managed through the vehicle EMC management plan, and EN 50121-3-1 covers the complete vehicle.
Related standards
EN 50155 sets the overall requirements for rolling-stock electronic equipment and refers to EN 50121-3-2 for EMC, so an EN 50155 type test programme normally includes EN 50121-3-2 emission and immunity tests. EN 50121 builds on the generic IEC/EN 61000 family: test methods come from the EN 61000-4 basic standards, and enclosure emission limits draw on EN 61000-6-4. Internationally, the IEC 62236 series follows the same structure. Which parts, editions and port tests apply should be agreed between buyer and supplier at tender stage.
Checklist
Use these points when writing a specification or comparing suppliers. Ask for EMC test evidence for the exact product configuration rather than relying on a datasheet label.
Scope: which part applies, EN 50121-3-2 for apparatus on rolling stock, EN 50121-4 for signalling and telecom apparatus in the railway environment, or EN 50121-5 for fixed power supply installations?
Edition: does the test report name the edition and amendment tested against, for example EN 50121-3-2:2016 with A1:2019?
Ports: does the report cover every power, battery, signal and communication port of the configuration being supplied, including long cable runs?
Immunity: were radiated and conducted RF, fast transient, surge and electrostatic discharge tests run, and which performance criterion (A, B or C) was declared and met for each?
Emissions: were conducted emissions on power ports and radiated emissions from the enclosure measured against the required limits?
Integration: how will the apparatus fit the vehicle or station EMC management plan, including cabling, earthing and shielding at installation?
Evidence and sourcing: will the supplier share the full EMC test report for the exact configuration, and does the programme favour Built in India / Make in India manufacturing?
Envision TechWorks
Envision TechWorks products are designed, manufactured and tested in an ISO 9001:2015 facility in India: production-ready and Built in India for Make in India programmes. PAPIS onboard passenger announcement and information hardware is built to EN 50155. Production includes in-circuit and functional test, AOI and X-ray inspection, and thermal cycling. Share the EN 50121 parts, editions and port tests named in your tender, and the team can discuss your requirements and build to your specification.
Related
The rolling-stock electronics standard that refers to EN 50121-3-2 for EMC, covering temperature classes, power supply, shock and vibration, and type tests.
Read the EN 50155 guide →Passenger announcement and information system for metro trainsets, with hardware built to EN 50155.
See PAPIS product details →Onboard and station IP surveillance with centralised video management and vandal-resistant cameras for rolling stock and stations.
See IP CCTV product details →Remote diagnostic and performance monitoring for locomotive and rolling stock fleets, with edge data acquisition and predictive maintenance alerts.
See RDPMS product details →Platform and concourse displays that show route maps, arrivals, service status and emergency messages on sunlight-readable screens, managed centrally from the control room.
See Station PIS product details →How selecting IP CCTV for rolling stock differs from platforms, with a selection checklist for housings, operating envelopes and video management.
Read the IP CCTV guide →FAQ
EN 50121 is the European series of standards for electromagnetic compatibility in railway applications. It sets emission limits and immunity requirements for the railway system as a whole, rolling stock, onboard apparatus, signalling and telecommunications apparatus and fixed power supply installations. IEC 62236 is the closely aligned international series.
Part 1 covers general requirements; Part 2 emission of the whole railway system to the outside world; Part 3-1 trains and complete vehicles; Part 3-2 apparatus on rolling stock; Part 4 signalling and telecommunications apparatus; and Part 5 fixed power supply installations and apparatus. The current parts date from 2016 and 2017, with A1:2019 amendments to Parts 3-1, 3-2, 4 and 5.
Electrical and electronic apparatus for use on rolling stock falls under EN 50121-3-2, which sets port-by-port emission and immunity tests. The complete vehicle is assessed under EN 50121-3-1, and signalling and telecommunications apparatus installed in the railway environment outside the vehicle falls under EN 50121-4.
EN 50155 is the overall standard for rolling-stock electronic equipment and refers to EN 50121-3-2 for electromagnetic compatibility. An EN 50155 type test programme therefore normally includes EN 50121-3-2 emission and immunity tests, alongside EN 61373 shock and vibration tests.
Envision TechWorks designs, manufactures and tests products in an ISO 9001:2015 facility in India, and PAPIS onboard hardware is built to EN 50155. Share the EN 50121 parts, editions and port tests named in your tender, and the team can discuss your requirements and build to your specification, Built in India.
Share the EN 50121 parts, editions, ports and mounting location named in your tender, and the team will discuss how to build to your specification, Built in India.