Signalling Power Circuit Principles
|Publication Date:||1 December 2008|
This standard applies to new functional signalling power circuits (both ac and dc) typically comprising busbars, protective devices, transformers, rectifiers and batteries fed from a functional supply point with a nominal output voltage of less than 175V, typically of the 2 wire IT type (non-earth referenced) and any operational equipment fed from such supplies.
This standard also applies to alterations to existing functional signalling power circuits and covers transitional arrangements for circuits not designed or installed in accordance with the standards for new installations.
This standard details the interfaces and agreements required between the designers responsible for the distribution system, switchgear and the functional supply point, and designers responsible for the functional signalling power circuits.
This standard does not include (in accordance with NR/GN/ELP/27310, Management of Signalling Power Supplies and NR/GN/ELP/27315, Management of Power Supplies for Telecomms Equipment):-
a) the distribution system (which includes cables, switchgear, transformers and backup systems),
b) supply equipment feeding a single item of equipment at nominal 175V or higher,
c) supply equipment and transformers with an input voltage of nominal 175V or higher,
d) Accommodation, maintenance and test equipment supplies (e.g. lighting and sockets for test equipment unless these are required to be from an IT-type (non-earth referenced) supply equivalent to that for signalling equipment).
The responsibilities for signalling power supplies have traditionally been with the signal and telecommunications engineers, however the distribution systems have been transferred to the electrification and plant engineer.
This standard states the requirements on designers, suppliers, installers and testers of functional signalling power supply circuits and equipment. Additionally it identifies the need for the designer of the functional circuits to agree load requirements and protection arrangements with the designer of the distribution system.