3.6　Earthing Conductor

3.6.1　Various earthing conductors within telecommunication bureaus（stations）shall be determined according to the maximum fault current value and the mechanical strength of materials，for which multistrand copper wires with the sectional area of 16mm2-95 mm2 should be selected.

3.6.2　Multistrand copper wires with the sectional area not less than 16mm2 shall be adopted for earthing conductors of internal main equipment in distribution rooms，power rooms and generator rooms.

3.6.3　Multistrand copper wires with the sectional area not less than 70mm2 shall be adopted for earthing conductors that are laid across different floors or at the same floor with long laying distance.

3.6.4　When the length of earthing conductors from the main earthing conductor at each floor to the floor earthing bars or equipment is relatively short，the multistrand copper wires with the sectional area not less than 16mm2 should be adopted；when the length is long，multistrand copper wires with the sectional area not less than 35mm2 should be adopted or one floor earthing bar should be added，which shall be firstly connected with the equipment via multistrand copper wires with the sectional area not less than 16mm2，and then connected to the floor earthing bar at each floor via multistrand copper wires with the sectional area not less than 35mm2.

3.6.5　Multistrand copper wires with the sectional area not less than 4mm2 may be adopted for earthing conductors of small-size equipment such as data servers，environment monitoring systems，data acquisition units and small-size optical transmission devices；when the earthing conductor becomes longer，its sectional area shall also be enlarged，or one local earthing bar may be added，besides，multistrand copper wires with the sectional area not less than 16mm2 shall be connected to the earthing bar.When the earthing conductor is installed in an open rack，multistrand copper wires with the sectional area not less than 2.5mm2 shall be connected to earthing bars at the rack，and such earthing bars shall be connected to the main earthing conductor via multistrand copper wires with a sectional area of 16mm2.

3.6.6　The earthing conductors of optical transmission system shall be in accordance with the following requirements：

1　In small-size bureaus（stations）such as access networks and mobile telecommunication base stations and the like，metal intensive cores and metal sheaths of optical cables shall be earthed reliably in the junction box，and multistrand copper wires with the sectional area not less than 16mm2 shall be used for leading to the main earthing terminal in the bureaus（stations）.

2　Metal intensive cores and metal sheaths of optical cables in telecommunication buildings，exchange bureaus and data bureaus shall be connected with the earthing bar in junction boxes or at ODF（Optical Distribution Frame），which shall be led to the nearby floor earthing bar via multistrand copper wires with the sectional area not less than 16 mm2；when it is far from the earthing bar，the earthing terminal led from the nearby main rebar of the pillar of transmission equipment room may be regarded as the earth point of the optical cables.

3　Multistrand copper wires with the sectional area not less than 10mm2 shall be adopted for earthing conductors of optical transmission rack or subracks.

3.6.7　Good electrical contact shall be ensured for the connection points at two ends of the earthing conductor.

3.6.8　Switches or fuses must not be installed in the earthing conductor.

3.6.9　The earthing conductors led out from the main earthing conductors shall have obvious signs.