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 MIL-HDBK-1012/1
boundary. Specific guidance concerning the treatment of such power and signal
cabling will be contained in the BESEP.
In general, primary power distribution and protection should be
outside classified areas to facilitate access for maintenance. Normal power
distribution design for electronic equipment areas requires consideration of
the peculiarities of communication and electronic equipment. For example,
low-level signals in the microvolt range and a large frequency spectral
environment would suggest that power lines be routed as far away as possible
from the nearest antenna. Radio-frequency noise sources such as generators,
air conditioning compressors, and switchgear should be located to minimize
physical and electrical interference with electronic equipment.
Voltage transient protection should be installed on both transient
sources and power distribution points for electronic equipment. Commercial
power conditioning equipment, containing instrumentation and alarm
capabilities as well as active and passive protection devices, may be
necessary to provide the quality of power appropriate to the equipment being
supported.
5.2.8
Electrical Distribution Systems. The electrical distribution
system shall be designed in accordance with NFPA 70 National Electrical Code.
Consideration should be given to providing a flexible system that will meet
the facility's future requirements. Electronic equipment is constantly being
upgraded, modified, and replaced. Bus duct systems and cable trays may prove
to be the most flexible system in areas where new equipment is expected or
where frequent modification may occur. The BESEP will provide equipment lists
with power requirements for each piece of electronic equipment, including
maximum load, voltage characteristics, and special requirements. All main
transformers serving electronic facilities shall have lightning protectors on
both the primary and the secondary side of the transformer.
5.2.8.1
Load Category. Each load category shall be fed as shown in
Figure 7.
5.2.8.2
Circuit Breakers. Separate circuit breakers shall be provided at
power panels for each equipment rack, cabinet, or piece of electronic
equipment. Individual pieces of equipment shall be connected to the
panelboards by wiring run in cable racks or conduits or a combination of both.
Bolt-on circuit breakers should be used in electronic facilities.
5.2.8.3
Cable Vaults. Most buildings require underground radio-frequency
cable, communication cable (telephone type), control cable, and power cable.
These cables shall enter the building through two cable vaults, one for signal
cables and one for power cables, These vaults shall also house the protective
devices used to prevent surges from entering the building. The vaults shall
be designed in accordance with the latest safety standards.
5.2.8.4
Wiring. Wiring to each piece of equipment shall be sized to carry
full load current. Maximum voltage drop shall be in accordance with NFPA 70.
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