scope:

This standard applies to equipment and systems on the LU power system.

This specification applies to new 630/750V d.c. indoor switchboards and extensions of existing equipment, associated equipment and documentation, to be installed on London Underground Network by LU or LU Suppliers within Traction Power substations or Track Paralleling Huts.

Purpose

This Standard states the technical requirements for the design, manufacture and testing of 750V rated d.c. indoor switchboards, associated equipment and documentation for providing power supplies to London Underground 630 - 750V nominal d.c. fourth rail electric traction system and in some cases for lifts and escalators. The supplies operate with both poles insulated from earth except where earthed through high ohmic value Traction Bleed Resistors for monitoring earth faults on the conductor rail system.

The switchgear is used to provide routine switching of the positive and negative poles of the d.c. power supplies, including the making and interruption of light load, load and fault current and the isolation of individual circuits and busbars within an operational environment as described in S1916 'Physical and Electrical Environment of The System'.

The switchboards typically consist of busbars, incoming rectifier circuits, outgoing track feeder circuits, feeder coupler circuits, busbar coupler circuits and outgoing auxiliary feeder circuits each with circuit breakers in the positive and negative poles.