Section 3:
SELECTION OF ELECTRIC POWER SOURCE
3.1
Policy. In electric power source selection, use the same criteria
employed for selection of electric power plants in NAVFAC DM-3, Mechanical
Engineering Series.
3.2
Economic Factors. Use the same criteria presented for economic
studies of electric generating plants in the NAVFAC DM-3 Series.
3.3
Electric Power Sources. The electric power supply for a major
shore activity usually will consist of three sources: primary, standby, and
emergency (alternate). In addition, some operations cannot tolerate any
electric power interruption, thus requiring uninterruptible power supply
(UPS) systems. MIL-HDBK-1190 Facility Planning and Design Guide, Chapter 7
under "Alternate Power Sources," indicates systems and functions authorized
to have alternate power sources and provides design criteria for such
alternate sources.
3.3.1
Primary. The primary or preferred source should have sufficient
capacity to provide for peak electric power demand during normal peacetime
operations.
3.3.2
Standby. The standby source should have enough capacity so that
the standby system can supply all of the minimum essential operating electric
load of the activity and, when added to the capacity of the primary source,
will provide a combined capacity sufficient to serve the estimated peak
demand under mobilization conditions. This "minimum essential operating
electric load" is the minimum electric power necessary to support the
absolutely essential operations of the activity, with illumination reduced
to a bare minimum and with all convenience loads and other loads (such as
hospital elevators, except the minimum required for patient and food
transportation) suspended. Where major intermittent loads, such as drydock
pumping, electric furnaces, electric welders, and wind tunnels, are
involved, it is necessary to determine whether concurrent operation of such
equipment can be avoided.
3.3.3
Emergency. The emergency sources, usually one or more
engine-driven, manual, or automatic-starting emergency generators, should
have sufficient total capacity to provide the electric power demand for vital
operations. Vital operations are those that can tolerate electric power
interruption only for relatively short durations. For certain operations,
the permissible electric power interruption is as long as 4 hours, for others
it is only l0 seconds. The latter condition will require automatic start
but the former condition may be manual start. The emergency source should be
of sufficient capacity to provide a continuous and adequate supply for vital
operations, but should be planned to bear a sound relation to the standby
service provided. Vital operations will normally be in two categories:
a)
Operations recognized by local, state, or national codes, and
b)
Operations determined as vital by the major claimant or user.
To qualify as a vital operation, the electric power outages must cause loss of
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