EMC in Railway Technology — EN 50121 explained.

From the megawatts of traction to the milliwatt sensor signal: in the railway environment everything must work together free of interference. The EN 50121 standard series turns this into testable requirements.

Secure railway EMC

The EN 50121 standard series

EN 50121 (Railway applications — Electromagnetic compatibility) governs both the railway's emissions and its immunity. It is divided into parts:

50121-1 — Fundamentals and definitions
50121-2 — Emissions of the whole system to the outside world (protection of neighbors and radio services)
50121-3-1 — Rolling stock: train / complete vehicle (system level)
50121-3-2 — Rolling stock: apparatus (component level, e.g. converters, displays)
50121-4 — Signaling and telecommunications equipment
50121-5 — fixed power supply installations

EN 50155 — Apparatus on the vehicle

EN 50155 is the product standard for electronic equipment on rolling stock (operating conditions, temperature, vibration and much more) and, on the EMC side, generally refers to EN 50121-3-2.

EN 50657 — Software on board

EN 50657 applies to software on rolling stock (derived from EN 50128). It defines process and safety requirements via Software Integrity Levels (SIL) — related to functional safety in automotive.

Frequently Asked Questions

Which part of EN 50121 applies to my device?

For a single device on the vehicle, EN 50121-3-2 (component level) is usually relevant, often together with EN 50155. Other parts apply to the whole installation and to the outside world. We clarify the exact scope on a project-specific basis.

Why is railway EMC so demanding?

Because enormous power differences meet: traction converters in the megawatt range next to sensitive signaling and safety technology. Clean separation, shielding and filtering are particularly critical here.

Sources: Railway News — EN 50121 Guide, Element — EN 50121. The applicable version of the standard is authoritative.