EN 50124-1 — Railway applications — Insulation coordination — Part 1: Basic requirements — Clearances and creepage distances for all electrical and electronic equipment

Scope

Sets the basic insulation-coordination rules — required clearances and creepage distances, and the withstand voltages that follow from them — for all electrical and electronic equipment used in railway applications, from vehicle traction circuits to fixed power-supply installations. Part 2 (also current, EN 50124-2:2017) covers overvoltages and their protection; both parts are companion standards, not alternatives.

Insulation coordination is the discipline of choosing air gaps, creepage paths and withstand-voltage ratings so that electrical equipment neither flashes over in normal service nor fails dangerously under a foreseeable overvoltage — and EN 50124-1 is where the railway sector fixes that discipline into numbers: overvoltage categories and pollution-degree classes for the railway environment, altitude-correction factors, minimum clearance and creepage-distance tables keyed to system voltage and insulation type, and the dielectric test voltages that verify them. It is a basic-safety, cross-cutting standard rather than a component product standard — every piece of electrical and electronic equipment on a vehicle or in a fixed traction-power installation, from a converter enclosure to a signalling relay, is designed against its tables. Part 2 covers the overvoltage phenomena (lightning, switching, earth faults) that Part 1's insulation levels are chosen to withstand. Both parts are harmonised standards under Implementing Decision (EU) 2023/2584 (Annex I rows 94 and 95), giving presumption of conformity with the corresponding electrical-safety essential requirements of Directive (EU) 2016/797, and are used throughout LOC&PAS and ENE-TSI conformity files. Electrical and electronic equipment designers, vehicle and fixed-installation integrators, and NoBos assessing electrical safety are the standard's daily users; it is a foundational reference alongside EN 50163 (supply voltages) and EN 50388-1 (traction power-supply compatibility).