TM 5-685/NAVFAC MO-912
Figure 2-3. Typical grounding system for a building.
project and of the equipment, fuel cost and avail-
flight control). Emergency situations include the
ability, installation cost, and personnel availability
handling of priority loads during power "brown-
outs" and sharing load responsibilities with prime
and cost. Factors related to prime movers must also
power sources during "brown-outs". Usually load
be considered: the diesel because of its relatively
shedding consists of a documented plan that in-
low cost and good reliability record, as well as its
cludes a method for reducing or dropping power to
ability to use liquid or gaseous fuel; the gas turbine
noncritical equipment. This plan should include an
for permanent standby plants because it is rela-
updated schematic for load shedding reference and
tively compact in relation to its high generating
"Truth Table" to ensure correct sequencing of drop-
capacity (desirable if the anticipated power con-
ping and restoring loads on the system. Plans for
sumption rate is high). The components of the typi-
load shedding are part of the emergency operating
cal power systems are briefly described in the fol-
instructions and vary from one facility to another.
The extent of load shedding and the sequence of
a. Prime movers are reciprocating engines, gas
dropping loads and restoring to normal are also
turbines, or other sources of mechanical energy
contained in the plan.
used to drive electric generators.
2-10. Components .
b. Governors control and regulate engine speed.
A governor must be capable of regulating engine
Standards for selection of components for an auxil-
speed at conditions varying between full-load and
iary power plant are usually based on the electrical
no-load and controlling frequency.
loads to be supplied, their demand, consumption,
c. Generators are machines (rotating units) that
voltage, phase, and frequency requirements. Also to
convert mechanical energy into electrical energy.
be considered are load trend, expected life of the