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TM 5-685/NAVFAC MO-912
6-1. Requirements.
the normal power source, the sensing devices are
activated and initiate a starting signal to the prime
A successfully operating auxiliary power generating
mover. An alarm circuit is also initiated at this time
system has several requirements. First, the equip-
to alert the operator that normal power has been
ment in the system must be selected with ease of
lost and the emergency unit has started. As the
operation and maintenance as prime consider-
prime mover approaches rated speed, excitation is
ations. Second, the equipment must be installed by
automatically applied to the generator. The power
competent personnel.
plant will then remain in this condition, i.e., rated
a. Adequate records must be kept during instal-
lation and operational shakedown so that any fu-
speed and voltage, until the operator closes the cir-
ture modifications can be implemented with mini-
cuit breaker connecting the emergency generator to
mal research. Third, the operating personnel must
the load. If the station has more than one generator,
be thoroughly trained in proper operating proce-
and the load requires more than one generator, the
dures. Training must include performance of main-
operator must initiate the synchronizing circuitry.
tenance as well as operation. Fourth, a detailed
Using the techniques provided in paragraphs 6-5
record keeping system must be instituted.
and 6-6, the operator must parallel the second gen-
b. The record keeping system must include a li-
erator with the first. If additional generators are
brary of the various equipment manufacturers' in-
required, they must be added to the system in the
structions, operating log sheets, routine mainte-
same manner. The operator can then adjust the
nance instructions, maintenance log sheets, and
governors and excitation controls to obtain the de-
piping and electrical drawings. The records should
sired load division and reactive power division be-
be assembled in binders or folders and stored in the
tween generators.
installation's engineering office for availability and
c. The automatic mode is similar to the semi-
automatic mode up to the point that the unit
6-2. Attended stations.
reaches rated speed and voltage. When the speed
and voltage have stabilized, if the unit is picking up
a. Attended stations have one or more operators
a completely dead plant, a closing signal is initiated
on duty around the clock or for a portion of the day
to the circuit breaker. The circuit breaker energizes
if the plant is not used full time. Plants that have
the desired loads. If the load demands more than
an operator on duty only for a portion of the day
one unit, as the second unit reaches its operating
sometimes require an operator's presence during
speed and voltage, automatic synchronizing cir-
the entire period that the plant is supplying power
cuitry is enabled. The speed of the incoming unit
to the system. Attended stations can be operated in
will be adjusted automatically, and when the syn-
a manual mode, a semi-automatic mode, or an au-
tomatic mode. If the plant is manned at all times,
chronizing relay is satisfied that the conditions are
the manual or semi-automatic mode is usually em-
correct, a closing signal to the circuit breaker for the
ployed. In the manual mode, the operator has com-
second unit will be sent. If additional units are
plete control of the power plant and would start the
needed, the automatic synchronizing circuitry will
prime mover, bring it to operating speed, apply ex-
be switched as the units become available. Once
citation to the generator, and close the circuit
normal power is again available, the procedure for
breaker to pick up the station load. When parallel-
returning the load to the normal bus is usually done
ing with another generator, the operator must per-
in the manual mode. Installations that permit par-
form the paralleling procedures described in para-
alleling with the electric utility system can
graph 6-6. If paralleling with the electric utility
retransfer without an interruption of power. If par-
system is desired, approval must be obtained from
alleling is not permitted, there will be a momentary
the utility and the need for special relaying, such as
outage when the switching is performed. Some in-
reverse power relays, must be determined. The pro-
s t a l l a t i o n s are designed with an automatic
cedures for parallel utility operation are described
retransfer to normal power. However, these are usu-
in paragraph 6-5.
ally the smaller-rated units that use a transfer
b. In the semi-automatic mode, sensing devices
switch arrangement rather than circuit breakers for
monitor the normal source of power. Upon a loss of
switching loads.

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