Is EN 50121 compliance mandatory?

Yes, for railway products placed on the European market, compliance with the relevant part of EN 50121 is typically required to demonstrate conformity with the EMC Directive and Technical Specifications for Interoperability (TSI).

What is the difference between EN 50121-3-1 and EN 50121-3-2?

EN 50121-3-2 applies to individual components (apparatus) tested in a lab. EN 50121-3-1 applies to the complete train vehicle, ensuring that when all those components are installed together, the total emissions are still within limits.

Does EN 50121 cover 5G interference?

Newer revisions of the standard are continuously updated to address modern radio frequency bands, including LTE and 5G, ensuring that railway operations do not disrupt public telecommunication networks.

Harmony in High Voltage: The Comprehensive Guide to the EN 50121 Series

Explore the EN 50121 series, the definitive European standards for Railway EMC. Learn how parts 1 through 5 manage electromagnetic interference across rolling stock, signaling, and power systems.

December 23, 2023 2:13 pm

What is the EN 50121 Series?

EN 50121 is the overarching family of European Standards titled “Railway applications – Electromagnetic compatibility (EMC).” It defines the requirements for ensuring that the complex electrical environment of a railway—ranging from megawatt-level traction power to milliwatt-level sensor signals—functions cohesively without interference.

The railway environment is electromagnetically unique. It involves moving electrical contacts (pantographs/third rails), high-power switching (inverters), and long conductors (rails/catenary) acting as antennas. The EN 50121 series is designed to manage both Emissions (noise generated by the railway) and Immunity (the railway’s resistance to outside noise). Compliance with this series is a mandatory requirement for CE marking and Interoperability (TSI) in Europe.

Decoding the Structure: Parts 1 to 5

The standard is split into specific parts to address different subsystems within the railway network. Understanding which part applies to your equipment is the first step in certification.

EN 50121-1: General principles and common definitions.
EN 50121-2: Emission of the whole railway system to the outside world (protecting neighbors and radio networks).
EN 50121-3-1: Rolling Stock – Train and complete vehicle (System level).
EN 50121-3-2: Rolling Stock – Apparatus (Component level, e.g., inverters, screens).
EN 50121-4: Signalling and Telecommunications equipment (Trackside and indoor).
EN 50121-5: Fixed Power Supply installations (Substations and switching stations).

The Goal: Coexistence

The primary objective of EN 50121 is internal and external coexistence.

Internal: Ensuring the traction converter (source of noise) does not disrupt the driver’s display or the axle counter (victim).
External: Ensuring the train passing by does not interfere with residential TV reception, mobile networks (GSM/LTE), or airport radars near the tracks.

Comparison: Which Standard Applies?

Part	Target Environment	Typical Equipment
EN 50121-3-2	On-Board the Train	TCMS Screens, Door Controllers, Passenger Wi-Fi.
EN 50121-4	Trackside & Signal Rooms	Point Machines, Eurobalises, Interlockings.
EN 50121-5	High Voltage Infrastructure	Transformers, Rectifiers, Circuit Breakers.
EN 50121-2	The Environment (boundary)	Assessment of the magnetic field at the railway fence line.

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