Shielding the Passenger: EN 50153 and Electrical Safety in Rolling Stock

What is EN 50153?

EN 50153 is the critical European Standard titled “Railway applications – Rolling stock – Protective provisions relating to electrical hazards.” It defines the safety requirements to protect persons—passengers, crew, and maintenance staff—from the risk of electric shock within a railway vehicle.

A train is a complex electrical environment containing high voltage traction circuits (up to 25kV AC or 3kV DC) alongside low voltage control systems. EN 50153 establishes the rules for “Protective Bonding” (grounding) and insulation coordination. Its primary goal is to ensure that no accessible metal part of the train becomes dangerously “live” in the event of an insulation failure, thereby preventing electrocution.

Core Concepts: Direct vs. Indirect Contact

The standard addresses two fundamental types of electrical hazards:

• Protection against Direct Contact: Preventing people from touching parts that are intentionally live (e.g., busbars, terminals). This is achieved through barriers, enclosures (IP ratings), and insulation.
• Protection against Indirect Contact: Protecting people when they touch conductive parts (like the metal car body or a handrail) that are not normally live but have become live due to a fault. This is achieved primarily through Protective Bonding.

The Importance of Protective Bonding

One of the most significant technical requirements of EN 50153 is the bonding resistance. The standard mandates that all exposed conductive parts (e.g., door frames, seat supports, bogie frames) must be electrically connected to the vehicle body, and the body must be connected to the rail (return circuit).

Fault Clearing: By ensuring low-resistance bonding, any short circuit to the frame immediately creates a high current flow that triggers circuit breakers or fuses, cutting off the power supply instantly.

Warning Labels and Capacitors

The standard also dictates the use of warning signage (the lightning bolt symbol) for high-voltage cabinets. Furthermore, it specifies rules for “stored energy” in capacitors. After power is cut, capacitors must discharge to a safe voltage level (typically <60V) within a specified time (often 5 seconds) to protect maintenance staff opening the box.

Comparison: Types of Protection