scope:

This standard applies to LU their suppliers and/or contractors and third parties.

The earthing system is a coordinated arrangement of suitably rated and connected copper conductors comprising:

a) The earth electrode formed by vertical rods, earth mat/mesh, reinforcement within structural piles or other suitable enduring low resistance conductors placed in the ground

b) The main earth bar (MEB)

c) Connections between the MEB and the earth electrode

d) Connection between the MEB and HV neutral earthing transformer/reactor/resistor

e) Connection of all protective earth (PE) conductors and earthing conductors (EC)

f) Connections to extraneous conductive parts, protective bonding conductors (PBC)

g) Connections between the MEB and the LV neutral earth link (NEL)

h) Connections for Users of the earthing system

i) Subsidiary earth bar (SEB)

j) Connections between the MEB and the SEB

k) Connections for Users to SEB

l) Transition earth bar (TEB)

m) Connections between the MEB and TEB

n) Connections for Users to the TEB.

Refer to Appendix C for the earthing conductor scheme diagram.

This standard for earthing systems, applies to all new electrical power system supply facilities including HV electrical substations, HV/LV auxiliary transformer rooms, HV switch rooms, bulk supply points (BSP), LV switch rooms, traction supply substations.

This standard for earthing systems, applies to all amendments, modifications, extensions and replacements at existing electrical power system supply facilities including; HV electrical substations, HV/LV auxiliary transformer rooms, HV switch rooms, bulk supply points (BSP), LV switch rooms, traction supply substations.

This standard is not applicable to intrinsically safe electrical systems for explosive atmospheres which shall comply with BS 7671, Appendix 2 and specifically; The Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations 1996.

This standard does not apply to Building Services which are covered under the requirements of S1069 'Low Voltage Electrical Installations' and are maintained and operated by the Building Services asset steward.

Purpose

This standard states the technical requirements for the planning, design, installation, testing and the records of earthing systems required for the safe operation of London Underground (LU) electrical systems at all voltages used for power transmission, distribution, traction power supply and other energy uses.