Fixed Installations for Railway Application — Electrical Safety, Earthing and the Return Circuit — Part 1: Protective Provisions against Electric Shock

Scope

Specifies protective provisions against electric shock in fixed installations of AC and DC electric traction power supply systems, including earthing and return-circuit requirements, and applies to railways, tramways, metros and trolleybus systems as well as to vehicles on electrified lines. Used by infrastructure managers, electrification designers and assessors for new traction power supply systems and major revisions. Part 1 of the three-part EN 50122 series; the 2022 edition is amended by A1:2025.

EN 50122-1, Part 1 of the three-part EN 50122 series on electrical safety, earthing and the return circuit for fixed railway installations, specifies the protective provisions required against electric shock in AC and DC electric traction power supply systems. It sets requirements for earthing arrangements and the design of the traction return circuit, covering both trackside fixed installations and their interfaces with vehicles operating on electrified lines, and applies across railways, tramways, metros and trolleybus systems. Infrastructure managers and electrification designers apply the standard when designing new traction power supply systems or undertaking major revisions to existing ones, using it alongside the applicable traction supply voltage ranges that define the electrical environment the earthing and return-circuit design must accommodate. Assessors reference it during the conformity assessment of energy subsystem installations under the applicable TSI. The current edition, EN 50122-1:2022, is amended by A1:2025, which introduced updates applicable from 15 August 2025.