standards and guidelines for communication sites - Radio And ...

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES MINIMUM SITE GROUNDING (EARTHING) REQUIREMENTS
• Installing a 16 mm 2 csa (#6 AWG) or coarser copper conductor (bonding jumper) between the
cable bridge/ice bridge and the tower ground bus bar (TGB). Conductor bonding to the cable
bridge/ice bridge and TGB shall be made using exothermic welding, or listed two-hole lugs and
stainless steel hardware. See “Bonding to the External Grounding (Earthing) Electrode System” on
page 4-40.
• Installing a 35 mm 2 csa (#2 AWG) or coarser, bare, copper conductor bonded directly to the
grounding electrode system. Conductor bonding to the grounding electrode system shall be made
using exothermic welding or listed irreversible high-compression fittings. Conductor bonding to
the cable bridge/ice bridge shall be made using exothermic welding, or listed two-hole lugs and
stainless steel hardware. The grounding conductor should be installed in a flexible non-metallic
conduit to help prevent incidental contact with other metals, allow for protection of the conductor,
and to help support the conductor.
In order to reduce the amount of lightning energy diverted towards the equipment building/shelter, and
to provide seismic isolation between the building and tower, it is recommended to secure the cable
bridge/ice bridge to the tower through a non-conductive slip-joint type device. When a slip-joint type
device is used, grounding of the cable bridge/ice bridge at the building shall be completed as described
above; grounding at the tower end of the cable bridge/ice bridge shall be completed as follows:
• Installing a 35 mm 2 csa (#2 AWG) or coarser, bare, copper conductor bonded directly to the
grounding electrode system. Conductor bonding to the grounding electrode system shall be made
using exothermic welding or listed irreversible high-compression fittings. Conductor bonding to
the cable bridge/ice bridge shall be made using exothermic welding, or listed two-hole lugs and
stainless steel hardware. The grounding conductor should be installed in a flexible non-metallic
conduit to help prevent incidental contact with other metals, allow for protection of the conductor,
and to help support the conductor. See Figure 4-52.
TOWER
GROUND RING
INSULATING A MA ATERIAL
SUCHAS FIBERGLASS
ISOLATING A
BRACKETT WITH
SLOT T ADJUSTMENT
ALLOWS FOR
SIESMIC MOVEMENT
TRANSMISSION LINE
ENTRY Y PORTS
EGB
FLEXIBLE
NONMETALLIC
CONDUIT
BONDING JUMPER
BUILDING
FIGURE 4-52 PROPER GROUNDING OF NON-SELF-SUPPORTING ICE BRIDGE
68P81089E50-B 9/1/05 4-73