NR NR/L2/SIG/11201/MOD B3 ISSUE 10 PDF

2.1 Inclusions

This module applies to the design of electrical circuits associated with:

a) electro-mechanical signalling systems;

b) electro-pneumatic signalling systems;

c) relay based signalling systems; and

d) electronic signalling systems.

It applies to both internal and external circuits, commencing on the load side of the final busbar.

2.2 Exclusions

It does not apply to wiring associated with the power supply side of the final busbar, which is covered in NR/L2/SIG/30050, nor to circuits associated with signaller’s voice communication systems, which are covered in NR/L2/TEL/30002, NR/L2/TEL/30031, NR/L2/TEL/30032 & NR/L2/TEL/30143.

For the presentation and use of circuit diagrams within the design process see NR/L2/SIG/11201, Module A2-8 & A4-8 Relay and circuit nomenclature, as well as symbols, are defined in NR/L2/SIG/11201, Module A5-2

2.3 Supporting Modules and other documentation

The following guidelines and specifications support the guidance within this module:

a) guidelines on fusing and looping in NR/L2/SIG/11201, Module B4;

b) guidelines on the electromagnetic compatibility of electronic equipment in NR/L2/SIG/11201, Module B5;

c) guidelines on protection of conductors for occupational safety, in NR/L2/SIG/11201, Module B6;

d) guidelines on the application of different types of circuit in the relevant parts of this standard;

e) the typical circuits listed in NR/GN/SIG/CAT005; and

f) the relay specifications listed in NR/LS/CAT006.

2.4 Consistency

The content of this module describes best practice requirements and guidance for adoption in ‘greenfield’ applications. Where greenfield new works abuts existing installations it is important to consider whether the use of current best practice would either be confusing or incompatible with the existing practice at the adjacent place.

It should not be presumed that adoption of the latest approaches needs to supersede or influence existing application design; it has to be a judgment as to where boundaries between different practices should lie and how much overlap gives the better compromise.

NOTE: As an often-encountered example in the design of line circuits, the British Railways, Western Region practice of fusing the negative polarity of DC power supplies contradicts the more usual practice of fusing the positive. Circuits with their origin in a Western Region locality should adopt the Western practice whereas those originating in an adjacent new works locality should follow that practice. This is practicable and sufficiently consistent because a relay load simply needs to be configured to accept the delivered incoming supply polarity and, when a neutral circuit, the polarity is actually of no consequence.

PURPOSE & INTRODUCTION

This module forms part of the Signalling Design handbook (SDH: NR/L2/SIG/11201) and is to be read in conjunction with the other modules of the handbook and reference documentation.

This Network Rail standard contains requirements and guidance on signalling engineering applications. The content supports the specific and general requirements described in Railway Group Standards and the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009].

NOTE 1: Where there is a conflict between this standard and a Railway Group Standard or the Network Rail Signalling Principles Handbook [NR/L2/SIG/30009] then this standard shall not take precedence.

Decisions made by a competent person should be supported by appropriate evidence or documentation.

NOTE 2: Use of designer notes on drawings (see HSE CDM guidance) will generally suffice as may Design Log entries.

Any adoption of alternative solutions requires an assessment commensurate with the significance of the proposed change and which follows the guidance provided by the Common Safety Method for Risk Evaluation and Assessment [CSM-RA]; Network Rail’s adopted method for the control of safety risks.