Switchboard and Distribution Monitoring and
Generator Monitoring and Control
The generator section of each SSDG is monitored
Power from the generator is monitored, controlled,
for control and synchronizing. Transducers pick up
and distributed through a system of meters, electronics,
parameters that need to be monitored and send them up
to the EPCC. The parameters are processed by the DDI
and circuit breakers. Under automatic operation, the
and the SCS and by alarm circuits and gauges.
EPCC can perform all three functions through the
processor software programs.
Current, voltage, frequency, and power readings are
available from the EPCC by dialing in the appropriate
T h e circuit breaker status of each SSDG is
address on the DDI or reading the parameters directly
monitored for the generator, bus tie, and load shed
off meters on the EPCC. Stator temperature is monitored
circuit breaker position. The EPCC will illuminate a
for each phase of the generator. This is the only meter
status indicator if the circuit breaker at the switchboard
on the EPCC that reads out in degrees centigrade rather
is different from the switch position at the EPCC. Vital
than degrees Fahrenheit. The status of the voltage
power circuit breakers, such as fire pump controls, are
regulator and fields exciter is indicated on the EPCC by
monitored at the EPCC on the vital power feeder circuit
two green lights: one for manual mode and the other for
breaker status panel.
automatic mode. Two more green lights on the EPCC
The main breakers for the generator set, load
monitor the state of the differential or droop selector.
sheddings, and bus ties are monitored on the EPCC.
T h e generator can be controlled through
Others, such as the radar room or seawater pump circuit
g o v e r n o r system, the voltage regulator, and
breakers, are also monitored but not controlled from the
synchronizer. The voltage regulator is used to vary
EPCC. Other functions that are monitored from the
field excitation that, in turn, controls the speed of
E P C C are power supplies, uninterruptible power
supplies (UPS), and the console heaters. At the EPCC,
the total output for the ac generation system is monitored
The governor controls the generator set in two
for frequency, voltage, and current. Individual bus ties
different modes: isochronous and droop. The
can be monitored for current loads by selecting each bus
isochronous mode is used to share the loading on the
tie with the rotary switch on the EPCC.
generators and yet keep a constant speed or frequency.
The amount of fuel to the diesel determines the load each
The generator can be taken off the line if REMOTE
generator can carry. In the droop mode, the frequency
control is given to the EPCC and the generator switch is
will vary as the load is changed, but only within
turned to the TRIP position. The switch will work in the
predefine limits. This predefine area of droop is O to
CLOSE position only if the paralleling mode switch is
6 percent of the bus frequency. The frequency of a
in the BYPASS or PERMISSIVE position and the
generator also can be controlled manually from the front
g e n e r a t o r switch is at the BUS position. The
panel of the EPCC. The increase/decrease knob will
PERMISSIVE mode permits manual closure of the
change the frequency higher or lower, when the operator
breaker only when the automatic paralleling device
needs to match a generator to a bus to parallel it.
(APD) senses the generator is in synchronization with
the power bus. The BYPASS disables the APD so
The voltage regulator controls the generator output
synchronization has to be accomplished manually. The
t h r o u g h the field excitation. The voltage can be
generator breaker is closed manually by the operator.
manually controlled from the respective switchboards,
except from switchboard No. 4. Switchboard No. 4 is in
The load shed circuit breaker is opened and tripped
the same space as the EPCC and has the manual voltage
b y the EPCC operator when the EPCC is in the
c o n t r o l on the EPCC panel. The manual preset
REMOTE mode. This circuit breaker can be manually
p o t e n t i o m e t e r s give the field excitation circuit a
or automatically tripped. The sensors from the generator
reference from which to work. The second mode is the
bus will trip all load shed circuit breakers when an
AUTOMATIC mode. The voltage regulator AUTO
overload condition is sensed. This action will remove
ADJUST potentiometer on the EPCC can raise or lower
the nonvital bus from the bus ring.
the voltage by controlling a motorized potentiometer on
As mentioned earlier, the manual voltage control for
the generator set. The motorized potentiometer sets a
the No. 4 switchboard is on the EPCC since the
limit for field excitation and voltage output. If the
voltage goes up, feedback causes the field excitation to
switchboard and the EPCC are both in the CCS. The No.
4 switchboard does not have a remote control mode;
drop, bringing the voltage back into tolerance.