MIL-HDBK-1025/10
during the period in which they are bonded to temporary grounds. When it is absolutely
necessary to work on or near these features, workers should use bonded conductive or
insulated platforms, or approved insulated shoes to minimize the hazard from step and
touch potentials. Bond separately grounded systems together if they can be
simultaneously contacted.
5.3.4 Temporary Grounding System Components. Use grounding
application (overhead, underground, substation) sets with ASTM F 855, Temporary
Grounding Systems to be Used in De-energized Electric Power Lines and Equipment,
grounding jumpers (clamps, ferrules, and clear 600-volt jacketed elastomer flexible cable)
to the maximum possible extent.
5.3.4.1 Grounding Clamps. Use the alloy (copper or aluminum) matching the
conductor or device to which it is attached and meeting or exceeding the current-carrying
capacity of the associated cable. Use smooth jaw clamps on buses to avoid surface
marring. Use serrated clamp jaws to bite through corrosion products for attachment to
conductors or metal products. Self-cleaning jaws are recommended for use on aluminum.
Never use hot-line clamps for grounding.
5.3.4.2 Grounding Cable. Cables will be preferably ASTM F 855, Type I of a
minimum 2/0 AWG copper selected to meet the fault current necessary as given for 15-
cycle substation duty and 30-cycle line use. See Table 22.
a. Derate these fault current by 10 percent when using multiple ground cables
(which should all be of the same size and length).
b. Handle cables to avoid conductor strand breakage from sharp bends or
excessive continuous flexing.
c. Avoid excessive cable length because an increased resistance can elevate
potential differences and twisting or coiling reduces the cable's current-carrying capacity.
d. Avoid very low temperatures; the clear jacket which allows checking for strand
breakage will stiffen at low temperatures and split or shatter.
e. Cables prepared by facility personnel for grounding applications should be
highly flexible but rugged.
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