3.4.3.5
Warning Tape
Direct burial cable shall be placed below a plastic warning tape buried in
the same trench or slot. A 0.127 mm (5 mil) 5 mil brightly colored plastic
tape, not less than 75 mm 3 inches in width and suitably inscribed at not
more than 3 m 10 feet on centers with a continuous metallic backing and a
corrosion-resistant 0.0254 mm (1 mil) 1 mil metallic foil core to permit
easy location of the buried cable, shall be placed approximately 300 mm 12
inches below finished grade.
3.4.4
Messenger Cable
3.4.4.1
Installation
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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 ground connection.
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Messenger shall be attached to poles with approved clamps and not less than
15.9 mm 5/8 inch through bolts. Messenger cable tensioning shall not
exceed 30 percent of its rated breaking strength under 16 degrees C 60
degrees F conditions of no ice and no wind. Messengers shall be stressed
to a tension higher than the final tension in order to prestretch the
cable, so that when the messenger is dead-ended under its final tension and
sag, there shall be minimum variation from the calculated values.
3.4.4.2
Grounding and Bonding Connections
Messengers shall be grounded and guyed at corners, dead-ends, and entrances
to each facility, and grounded at intervals not exceeding 300 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.] Connections below grade shall be fusion welded. Connections
above grade shall be fusion welded or shall use UL 467 approved connectors.
3.4.4.3
Grounding Conductors and Electrodes
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 ground rod of [copper clad steel
conforming to UL 467] [zinc coated steel conforming to ANSI C135.30] [solid
stainless steel] not less than [15.9] [19.1] mm [5/8] [3/4] inch in
diameter by [2.4] [3.1] mm [8] [10] feet in length. 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.
3.4.4.4
Ground Resistance Testing
The resistance to ground shall be measured using the fall-of-potential
method described in IEEE Std 81. The maximum resistance shall not exceed
25 ohms under normally dry conditions. Whenever the required ground
SECTION 16528A
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