structural loading allow addition of cables. Where
this is not possible, requirements must be shown on
the drawings. Installations will comply with IEEE
C2 for Grade B construction and NFPA 70. Designer
must coordinate with facility personnel for ground
clearance and establish clearances to be shown on
the drawings.
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Except as otherwise specified, aerial electrical work shall be installed as
specified in Section 16370A ELECTRICAL DISTRIBUTION SYSTEM, AERIAL and as
shown.
3.1.5.8
Messenger System
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NOTE: The designer will verify local electrical
installation requirements to determine if new
grounding conductors and electrodes are required at
each messenger cable grounding connection and will
select the first, or second, or both bracketed
entries as determined to be necessary.
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Furnish and install a messenger system to support aerial cables.
Messengers shall be attached to poles with approved clamps and not less
than 16 mm 5/8 inch through bolts. The messenger cable shall be stressed
prior to lashing the cables to a tension higher than the final tension.
This will prestretch the cable and ensure that there's minimum variation
from the calculated values when the messenger is dead-ended under its final
tension and sag. Messengers shall be grounded and guyed at all corners,
dead-ends, entrances to each facility, and grounded at intervals not
exceeding 305 m 1000 feet. [New grounding conductors and electrodes shall
be provided at each ground connection.] [Where grounding connections are
made in the vicinity of existing grounding conductors and electrodes, the
grounding connection may be made by a bolted or welded connection to the
existing grounding conductor.] Ground conductors shall be soft drawn
copper, having a current capacity of at least 20 percent of that of the
messenger to which it is connected. Ground conductors shall not be smaller
than No. 6 AWG. The ground conductor shall be connected to a copper or
copper clad steel ground rod not less than 19.1 mm 3/4 inch in diameter,
and length shall be as needed to achieve the specified ground resistance.
After installation is completed, the top of the ground rod shall be
approximately 300 mm 1 foot below) finished grade. The ground conductor
shall be protected by half-round wood, plastic, or fiber molding from the
ground to a point at least 2.4 m 8 feet above the ground. Ground
resistance shall be measured in normally dry conditions, not less than 48
hours after a rainfall, and the total ground resistance shall not exceed 25
[_____] ohms.
3.1.5.9
Aerial Cable Splices
Splices in aerial cable shall be within 1 m 3 feet of a pole and placed
inside a watertight enclosure. Drip loops shall be formed at the cable
entrance to the enclosure. Lashing clamps shall be placed within 300 mm 12
inches of the enclosure.
SECTION 16794A
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