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 MIL-HDBK-419A
1.11.2.5.2.5.3 Earth Electrode Subsystem. The earth electrode subsystem of each shelter shall be inter-
connected by two bare copper cables (see Figure l-100). Tie all shelter earth electrode subsystems together to
form a common earth electrode subsystem (reference Table l-22 for appropriate size cable to be used).
1.11.2.5.2.5.3.1 Power Ground. All grounded (neutral) conductors of each shelter should be grounded to the
earth electrode subsystem via the power entrance panel.
1.11.2.5.2.5.3.2 Signal Ground. The signal reference subsystem (skin or shelter) should be grounded at the
earth electrode subsystem at a single point.
1.11.2.5.2.5.3.3 Safety/Equipment Ground (Green Wire). The equipment grounding conductors of each shelter
are connected to the ground bus at the power entrance panel which in turn is grounded to the earth electrode
subsystem.
Reference 1.11.2.5.2.4 for this requirement. If additional
1.11.2.5.2.5.3.4 Lightning/EMP Protection.
lightning protection is required, each air terminal with its associated down conductor should be grounded to a
ground rod of the earth electrode subsystem. This requirement may necessitate the installation of additional
ground rods.
1.11.2.6 Fixed Prefabricated Shelters.
1.11.2.6.1 General Description. Fixed prefabricated shelters are generally designed having the major
components prefabricated and then assembled on-site into a fixed shelter which can be considered as a fixed
facility. As such, it will have its own earth electrode subsystem (ring ground) meeting the requirements of
Section 1.2. It should also have a lightning protection subsystem meeting the requirements of 1.11.1.1.3.1
whenever the shelter is located outside the cone of protection of a higher grounded tower. The shell of metallic
prefabricated shelters should be constructed to be electrically continuous and grounded to the earth electrode
subsystem to bleed off static charges and reduce the effects of interference to C-E equipments and circuits. If
metallic and electrically continuous, the skin of a fixed prefabricated shelter may serve as the equipotential
plane. If the skin is not metallic or electrically continuous, a separate equipotential plane meeting the
requirements of Section 1.5 will be required.
1.11.2.6.2 Electrical Connection. If the skin of the shelter is metallic, and electrically continuous, it shall be
bonded to the grounding (green) cable of the fault protection subsystem at the first service disconnect or the
power entrance panel which, in turn, is grounded to the earth electrode subsystem by the shortest route. Both
the grounded (neutral) and grounding (green) wires are bonded together inside the first service disconnect, and
grounded to the earth electrode subsystem. The grounded wire may, however, be lifted from ground if hum or
noise problems are encountered when one power source supplies power to two or more shelters.
l-190
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