scope:

Purpose

This guidance note is intended to help explain Network Rail's requirements for earthing and bonding when installing plant and equipment on 25 kV A.C. Electrified Lines. The reasons for Earthing and Bonding are:

• Provide safe return path for traction load current;

• Ensure a good return path for fault current and therefore circuit breaker operation;

• Maintain the potential of all accessible metalwork at a safe level and avoid differential earth voltages;

• Limit the effects of traction or fault current flowing in metallic services, cables and un-electrified lines;

• Prevent arcing at flammable gas or oxygen installations.