Specification for Class II Based Signalling Power Distribution Systems
|Publication Date:||6 June 2015|
This specification defines system design requirements, constraints, protection, cable sizing strategy, earthing and bonding arrangements. It also includes installation and testing requirements for a Class II based signalling power distribution system.
The requirements in this specification are to be applied to new or altered Class II installations of a complete feeder originating from a PSP (not precluding ASP, SSP, DITA or other power source) using enhanced unarmoured cable.
The requirements in this specification may also be applied to legacy Class I feeders, which may comprise any of the following electrical systems:
a) IT individual,
b) mix of IT individual and IT grouped, or
The modification and alteration of BS 7671 compliant signalling power distributions systems comprising IT collective or TN electrical systems is excluded from this specification.
NOTE 1: Only IT electrical systems form part of the risk assessment which supports the Class II safety case.
Functional circuits downstream of FSP isolating transformers are excluded from the provisions detailed in this specification.
This document specifies the requirements for the design, installation, and testing of Class II based signalling power distribution systems on Network Rail managed infrastructure. This specification also includes requirements for the introduction of Class II equipment into legacy signalling power distribution systems to provide fault protection.