UIC Leaflet 895: Technical Specification for Insulated Electrical Cables for Railway Vehicles

What is UIC Leaflet 895?

UIC Leaflet 895 is the international standard titled “Technical specification for the supply of insulated electrical cables for railway vehicles.” It establishes the mandatory quality and safety criteria for the vast network of wiring found in modern Rolling Stock.

Whether for high-voltage traction power, auxiliary systems, or low-voltage control circuits, these cables must operate reliably under harsh conditions, including constant vibration, temperature fluctuations, and exposure to oils and cleaning chemicals.

Technical Delivery Conditions

The leaflet provides detailed Technical Delivery Conditions for manufacturers. Because a cable failure can lead to a fire or total loss of train control, the standards for Insulation and conductivity are higher than those for general industrial use:

• Conductor Quality: Requirements for high-purity, flexible copper strands to prevent fatigue breakage caused by vehicle vibration.
• Insulation Integrity: Specifications for dielectric strength to prevent short circuits, especially in high-humidity or high-temperature environments.
• Mechanical Protection: Standardized tests for abrasion resistance and flexibility (minimum bending radii) to ensure cables can be safely routed through tight conduits in Tractive Units.

Fire Safety and Environmental Requirements

Perhaps the most critical aspect of UIC 895 is its focus on Fire Safety. In the enclosed environment of a train or tunnel, cable fires are extremely dangerous.

• Flame Retardancy: Cables must be self-extinguishing and must not propagate fire along the length of the cable tray.
• Low Smoke and Halogen-Free: Modern standards derived from UIC 895 mandate “LSZH” (Low Smoke Zero Halogen) materials. This ensures that if a fire does occur, it does not produce dense black smoke or corrosive acid gases that impede evacuation.
• Chemical Resistance: The outer sheath must resist degradation from ozone, UV light, mineral oils, and diesel fuels.

Application in Passenger and Tractive Stock

UIC 895 categorizes cables based on their application:

• Power Cables: Used for traction motors and pantograph connections.
• Control and Data Cables: Used for the Train Communication Network (TCN), signaling, and door controls.
• Auxiliary Cables: Used for lighting, HVAC, and passenger amenities in Passenger Coaches.

Comparison: Standard Industrial vs. UIC 895 Railway Cables