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

GROUNDING (EARTHING) SYSTEM COMPONENTS AND INSTALLATION REQUIREMENTS CHAPTER 5: INTERNAL GROUNDING (EARTHING)
Split Bolt or
irreversible crimp
Equipment grounding
conductor or ground
bus conductor
• Ground bus conductors shall be routed using the shortest possible routes. They may extend
into an adjoining subsystem equipment area and may serve as the grounding conductor for a
SSGB or a RGB. These ground bus conductors may have ground bus extension conductors to
provide a ground bus within cross section segments of a cable tray system. These ground bus
extension conductors shall be of the same specification as the ground bus conductor and shall
be routed with all connections to the ground bus conductor pointed in the direction of the MGB
or SSGB.
To MGB, SSGB or
ground system
Small hole
From equipment or object
to be grounded
Bolt with nut and
lock washer
Lug
Ferrous
material
Inside of cabinet
or structure
Conductors of different groups must
be adequately separated on either
side of the hole or opening.
Equipment
grounding conductor
or ground bus conductor
From equipment or
object to be grounded
Large hole or
opening
Ferrous
material
Other
Conductors
FIGURE 5-14 CONDUCTOR ROUTING THROUGH HOLES OR OPENINGS IN METALLIC SURFACES
• Bending radius: Ground bus conductors of all sizes shall maintain a minimum bending radius of
203 mm (8 in.). The angle of any bend shall not be less than 90 degrees (NFPA 780-2004,
Section 4-9.5). See Figure 5-13 on page 5-19.
• Separation:
• All ground conductors shall be separated a minimum of 51 mm (2 in.) from conductors of
other cable groups as defined in “Cable Trays” on page 3-18, and “Cable Separation and
Grouping within Racks and Cabinets” on page 9-12. Grounding conductors may come in
contact with other cable groups if they cross at a 90 degree angle and the crossing angle can be
maintained. An exception may be when conductors are grouped together to enter or exit a
cabinet or enclosure. Grouping only at this point is acceptable, provided the conductors are
suitably separated on either side of the opening.
• To minimize potential inductive effects when routing a grounding conductor through ferrous
material, the conductor shall be separated from the ferrous material by a distance of at least
51 mm (2 in.) where achievable, or the grounding conductor shall be effectively bonded to the
ferrous material. See Figure 5-14.
5-22 68P81089E50-B 9/1/05