scope:

This Guidance applies to all 630V d.c. and 750V d.c. circuits derived from traction substations. The d.c. Traction Supply system nominal voltage shall be 630V or 750V as defined in LU Standard 1-122 for the various Underground Lines, which includes the range of operating voltages to be expected. For the purposes of this standard, 'd.c. circuits' and 'd.c. protection' systems refer to these nominal voltages throughout this standard.

Excluded from the scope of this Standard is the calibration and maintenance of protection equipment.

This Standard applies to all new installations in its entirety and to existing installations where the necessary hardware exists to enable full compliance.

This standard replaces G-111 A1.

Purpose

The purpose of this Guidance is to provide guidance on each clause of the Standard S1111 together with informative attachments on particular protection systems. This document is structured such that each clause of the Standard is given followed by guidance. The clause numbering replicates the numbering used within the Standard for ease of cross-reference.

The purpose of this Standard is to define the requirements for the determination of protection settings and for the commissioning of d.c. protection systems to ensure that protection systems will function correctly for the conditions specified in this Standard.