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 MIL-HDBK-232A
5.1.2.5 Equipotential ground plane. To function properly the equipotential
ground plane must extend under or above all RED and BLACK equipment,
distribution frames (DFs), etc. It will also he connected at regular
intervals to the EESS and at every convenient point to metallic structural
members of the building. The facility design should include specifications
for where and how the plane will be installed and connected to the earth
electrodes and facility structure. (See MIL-HDBK-419.)
5.2 Power distribution. The power distribution system must accomplish two
objectives. First, it must provide quality power, free of abnormalities
which could cause loss of synchronization, discontinuity of switching
functions, or physical damage to the system. (See MIL.HDBK-411.) Second, it
must be designed to provide electrical protection of classified information,
and the equipment processing that information from EMP, electromagnetic
interference (EMI)/radio frequency interference (RFI), and TEMPEST hazards,
as required. The design and installation of the power system involves two
components - the power source and the facility load. The design requires
judicious selection of the primary and auxiliary power sources, UPS or other
power conditioning equipment, secondary substations, protective measures, and
the distribution system in order to attain the maximum overall system
performance with the most cost effective design. The designer is cautioned
to check local electrical codes when engineering facilities in overseas
locations.
5.2.1 Source. The ideal situation is to have the prime power source for the
facility located totally within the controlled space (CS). This would imply
a power generation station located within the CS. Since this situation
applies only to a few facilities, other options must be explored. Guidance
for power source installation is contained in MIL-HDBK-411.
5.2.1.1 Self-generated power. The objective of self-generation is to
provide isolated power which is distributed only to the facility and is not
shared with other activities (see figure 17). This isolation ran be realized
using MG and no-break generator sets. An MG consists of an ac or de motor
driving a generator. If the drive shaft connecting the motor to the
generator consists of nonconductive sections, the MG not only provides clean
isolated power, but may satisfy EMP/TEMPEST isolation requirements (see
figure 18). A no-break generator set is similar to an MG in that an ac or de
motor normally drives the generator. The generator includes an inertia wheel
connected to a diesel engine. When prime power is lost, the inertia wheel
keeps the generator supplying power while the engine is started and brought
up to operating speed.
5.2.1.2 Uninterruptible power. Many facilities in recent years have used an
UPS. These UPS are intended to provide stable, clean power for the mission.
Any UPS system must be evaluated to determine the extent of isolation between
the power line and the service loop. Where an UPS used, and separate RED and
BLACK feeds are required, separate UPS may be considered (see figures 19 and
20). Some UPS include a bypass mode which connects the load to the incoming
line in case of UPS failure. This feature cannot he employed when the UPS
feeds RED equipment.
5.2.1.3 Base power. In most instance, the facility will be provided with
commercial or base power. Either source requires the most stringent controls
to ensure isolation and prevent distribution of compromising emanations by
power-line conductions (PLCs). Three configurations of the source may be
encountered (see 5.2.1.3.1, 5.2.1.3.2, and 5.2.1.3.3).
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