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 MIL-HDBK-419A
1.3.3.4 Cable Installation and Grounding. Cables which enter a facility shall be installed generally using
Figure 1-31 as a guideline. The final design shall rest with the designer; however, the following steps apply in
general. (Figures 1-32 and 1-33)
Remove outer cable jacket very carefully so as not to damage the cable shield (see Figure 1-33,
a.
step 1).
Preform ground strap to fit cable diameter and secure the first hose clamp as outlined in the next
b.
step (see Figure 1-33, step 2)
Fold back ground strap (about 3.2 cm (1-1/4") long) over hose clamp and cable for a snug fit. Secure
c.
second hose clamp around the folded strips of the ground strap described in the next step (see Figure 1-33,
step 3).
For small diameter cable use a No. 6 AWG 7-strand copper wire with a lug connector on the other
d.
end. Secure the stranded cable using the same method as for the strap.
e.
After attaching all ground straps, tape (weatherproof) the exposed area.
1.3.3.5 Lightning-Generated Transient Surge Protection. Electrical and electronic equipment at various
facilities has been severely damaged by lightning-generated transients. The transients occur on externally
exposed lines that directly interface equipment. Externally exposed lines are outside lines, buried, overhead,
etc, that are exposed to weather elements. The lines include incoming ac service conductors, and equipment
signal, status, control, grounding conductors and intrafacility ac and dc powerlines. This section identifies
transient source and damage, waveforms and amplitudes of projected transients on different types of lines,
frequency of transient occurrence, and effective methods to implement to preclude equipment damage and
operational upset when transients occur.
1.3.3.5.1
Transient Source and Equipment Damage.
Electrical and electronic equipment comprising an operating system is susceptible to damage from
a.
lightning-generated transient surges via two primary sources as follows:
(1)
Transient surges coupled to equipment from incoming commercial ac power conductors.
(2) Transient surges coupled to equipment by connected facility control, status, power, ground,
data and signal lines that originate or terminate at equipment located externally to the building or structure
housing the equipment of interest.
Damage resulting from lightning-generated transients occurs in many forms. Entire equipment
b.
chassis have been exploded and burned, and wall-mounted equipments have been blown off the wall by large-
magnitude transient energy. However, two forms of damage are most prevalent and are listed below:
(1)
Sudden catastrophic component failure at the time of transient occurrence.
(2)
Shortened operating lifetime of components resulting from over-stress at time of transient
occurrence.
1-49
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