scope:

This standard defines Network Rail's requirements for IMDs and IFLSs for use on Isolated Terra (IT) Electrical Systems where the nominal system voltage does not exceed 1000 V a.c. or 1500 V d.c. for the following applications:

a) the interface between the Principal Supply Point (PSP)/Auxiliary Supply Point (ASP) and the Functional Supply Point (FSP);

b) the interface between an FSP and another FSP;

c) the interface points along a distribution feeder where a Distribution Interface Transformer Assembly (DITA) or Booster or Isolation Transformer has been installed;

d) Signalling Functional Circuits (a.c. and d.c.);

e) Traction derived power supplies interfacing with Principal Supply Point (PSP)/Auxiliary Supply Point (ASP);

f) Standby generator supplies interfacing with Principal Supply Point (PSP)/Auxiliary Supply Point (ASP);

NOTE 1: The nominal voltages used on SPSs are: 110 V; 230 V; 400/440 V and 650 V a.c.

The nominal voltages for Signalling Functional Circuits are typically 110/140 V a.c. 50/120 V d.c.

NOTE 2: Boundaries between subsystem elements are detailed in NR/L2/SIGELP/27416.

The following integrated systems and sub-systems are specified:

• Integrated solutions for the deployment of IMDs and IFLSs using a Tier 1, Tier 2 or Tier 3 architecture (see section 6.1);

• The interface of IMDs and IFLSs with Intelligent Infrastructure Systems.

IMDs and IFLSs as specified in this specification may also be used in other railway LV applications, e.g. car park charging points, tunnel lighting, traction transformer to PSP distribution, etc

Purpose

The purpose of this standard is to define Network Rail's requirements for Insulation Monitoring Devices/Systems (IMDs) and Insulation Fault Location Systems (IFLSs).

This standard is one of a suite of Network Rail standards that contribute to managing the electrical and operational safety risks. Compliance with this standard will satisfy that IMDs and IFLSs are manufactured, integrated and tested in accordance with Network Rail's requirements as defined in this document