IET Guide to Earthing and Bonding for AC Electrified Railways

The complexity of integrating the earthing of an AC electrified railway with various electrical distribution systems and exposed conductive parts means that it is impossible to prescribe one earthing and bonding design solution that addresses the needs of every railway. Therefore, different earthing designs are needed for individual railways.

This new Guide describes the underlying principles and typical configurations for the earthing and bonding of electrical traction system assets and other lineside assets and structures to reduce hazards to people and failures to equipment and systems. It also aims to assist infrastructure owners, railway designers and installation contractors in adopting a harmonised approach towards earthing and bonding design philosophy for AC railway infrastructure.

The work has been split into 11 sections covering:

• Introduction
• AC traction electrification distribution system
• Mass of Earth as part of the traction return system
• Traction return requirements and circuit configuration
• Protection against electric shock
• Electrification system assets excluding the traction return
• Assets not forming part of the traction return
• System measurements
• Lightning protection for railway structures
• Earthing and bonding at AC/DC interfaces
• Safe working during maintenance, renewal and decommissioning.

This new Guide explains the principles of a 'common earth' system (traction and non-traction) which is able to provide a robust and low impedance path to Earth.