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TM 5-685/NAVFAC MO-912
6-3. Unattended stations.
load, readings should be taken according to the op-
erating log developed for that station. When the
Unattended stations operate without an operator in
unit is no longer required and the load has been
attendance. Their operation is the same as an at-
removed, operate the engine at no load, or at some
tended station used in the automatic mode.
preset idle speed to allow the engine to cool gradu-
6-4. Nonparalleled stations.
ally. When the cooling period has expired, shut the
engine down. Cooling periods vary for different
a. Nonparalleled stations are those stations that
prime movers. Refer to manufacturer's instructions.
do not have provisions for connecting the emergency
generator bus to the commercial bus. It also applies
Stop the auxiliaries that do not stop automatically.
to a station that has a tie breaker between two
Make an inspection of the unit, looking for any
incoming lines that, because of electric utility regu-
unusual conditions.
lations, cannot be connected together. Electrical in-
e. It is essential that each power generator have
terlocks are used to prevent an unwanted parallel-
a complete set of standard operating procedures.
ing from occurring. These interlocks usually consist
The procedures include an up-to-date one-line dia-
of two circuit breakers electrically connected. The
gram of the electrical system showing the genera-
arrangement is such that only one circuit breaker
tors and the associated switchgear components (see
can be in the closed position at a time, thus prevent-
fig 6-l). Notes and legends are usually included
ing paralleling.
with the diagram.
b. In some arrangements, mechanical interlocks
AS Ammeter Switch
may also be provided. A mechanical interlock is a
VS Voltmeter Switch
device that physically prevents both circuit break-
WM Wutt-hour Meter
WHDM Wutt-hour Demand Meter
ers from being closed at the same time. This method
VAR Volt-Ampere Meter
CPT Control Power Transformer
also prevents paralleling from occurring.
PT Potential Transformer
CT Current Transformer
G1,G2 Generators
FU Fuse
c. Immediately before starting the prime movers,
make a thorough inspection to insure that the fol-
f. Before the unit is started an inspection should
lowing is in order. Verify that engine generator is
be made. This can be done in conjunction with the
inspection of the prime mover. Look for any mate-
not set to operate in a semi-automatic or automatic
rial or loose parts that could be drawn into the
starting mode during prime mover inspections. If
generator. Make sure that the air flow will not be
not, extreme caution should be used. Unexpected
start of prime mover while inspecting can lead to
restricted either on the intake or exhaust.
severe injury or death. Check for leaks in the lubri-
g. When the prime mover has the generator at
cating system, the fuel system, and the cooling sys-
operating speed, excitation can be applied. Adjust
tem. If any of the auxiliaries are belt-driven, check
the voltage regulator until the generator is at rated
for tightness of the belts. Check for proper levels of
voltage. Adjust the governor control for the prime
oil, water and fuel. Look for tools or other loose
mover so that the generator is at rated frequency.
Close the main circuit breaker connecting the gen-
objects, such as rags, that may have been left in the
area, and remove. If air pressure is a part of the
erator to the load. If necessary adjust the voltage
starting system, make sure the air pressure is at
control for rated voltage and the governor control
the correct value. Verify that none of the intake air
for rated frequency. Readings of various parameters
vents or exhaust ports are blocked. Start auxiliary
are taken according to the operating log for that
pumps (lube oil, fuel or water) that are necessary
station. Care must be taken so that the generator is
operated at or below its nameplate rating. After the
prior to running the unit.
unit has been shut down, a visual inspection similar
d. When the preparations for starting have been
to that performed prior to startup can be performed.
completed, a start signal is given to the prime
h. Proper operation of the switchgear requires a
mover. The engine (prime mover) should start to
knowledge of the standard operating procedures
rotate and, under control of the governor, accelerate
and the familiarity with the one-line diagram of the
to idling speed. Once the speed has stabilized, read
electrical system. It requires some knowledge of the
the pressure and temperature gauges to make sure
various protective relays and other devices associ-
that normal pressure and temperatures are being
ated with the system. The operator must be able to
maintained. Listen to any unusual noises. Shut the
recognize an impending problem by observing the
engine down if any unusual pressures or tempera-
meters or other indicators. The operator can then
tures are observed, or if unusual noises are heard.
take proper action. The operator must be able to
Be familiar with the engine manufacturer's litera-
perform some basic troubleshooting and mainte-
ture for information on acceptable pressures and
temperatures. Once the unit has been placed under

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