scope:

This standard applies only to the earthing and bonding of SSI installations on Network Rail Infrastructure. It applies to all new schemes and should be considered as part of any alteration to existing installations. Care must be taken when installing other types of equipment at SSI locations to ensure that the installation of that equipment does not compromise the provisions of this standard.

Purpose

This system specification defines the special requirements in design, manufacture, installation and maintenance that are essential for providing a safe earthing and bonding system for Solid State Interlocking (SSI) installations. Such a system must:

• ensure fast and efficient operation of protective equipment in the case of earth faults which might otherwise be undetected;

• protect against danger due to installation metalwork being maintained at a dangerous potential relative to earth;

• minimise the effects of interference from electrical surges such as switching transients, flashovers from the traction supply and lightning strikes on the SSI Equipment.