scope:

This document mainly covers railway signalling wires and cables with copper conductors. The conductors in wires and cables with natural rubber insulation are tinned and surrounded by an external layer of polychloroprene. The colours mentioned are those most commonly found, but some types are available in other colours. Known problems with cables of other types are mentioned. Except where specially mentioned, references to 'cables' may be taken as also applying to wires (i.e. single insulated conductors without an overall sheath). Testing methods are also included. The requirement to test insulation applies to cables, wires and circuit components carrying signalling circuits. This includes cables, interlockings, apparatus cases and lineside signalling equipment.

PURPOSE

This document provides information relating to cables and wiring insulation, both degradation that has been encountered on Railtrack Signalling Infrastructure and testing methods. It also contains relevant technical information and the historical background. Some notes on inspection techniques, alterations to affected wiring and some miscellaneous cable problems are included in the appendices. The purpose of insulation testing is to detect the deterioration or failure of the insulation of wires, cables and other circuit components. Testing may be by continuous monitoring or by regular testing depending on the required level of integrity.