Switchboard and Distribution
parameters that need to be monitored and send them up
Monitoring and Control
to the EPCC. The parameters are processed by the DDI,
the SCS, and alarm circuits and gauges.
Power from the generator is monitored, controlled,
At the EPCC, the operator can obtain current,
and distributed through a system of meters, electronics,
voltage, frequency, and power readings by dialing in the
and circuit breakers. Under automatic operation, the
appropriate address on the DDI or by reading the
EPCC can perform all three functions through the
parameters directly off meters on the EPCC. Stator
procesor software programs.
temperature is monitored for each phase of the
The circuit breaker status of each SSDG is
generator. This is the only meter on the EPCC that reads
monitored for the generation, bus tie, and load shed
out in degrees centigrade rather than degrees Fahrenheit.
circuit breaker position. The EPCC will illuminate a
The status of the voltage regulator and fields exciter is
status indicator if the circuit breaker at the switchboard
indicated on the EPCC by two green lights, one for
is different from the switch position at the EPCC. Vital
manual mode and the other for automatic mode. Two
power circuit breakers, such as fire pump controls, are
more green lights on the EPCC monitor the state of the
monitored at the EPCC on the vital power feeder circuit
differential or droop selector.
breaker status panel.
The generator can be controlled through the
The main breakers for the generator set, load
governor system, the voltage regulator, and the
shedding, and bus ties are monitored on the EPCC.
synchronizer. The voltage regulator is used to vary the
Other circuit breakers can also be monitored, such as
field excitation that, in turn, controls the speed of the
those in the radar room or seawater pump. These circuit
breakers are monitored but not controlled from the
The governor controls the generator set in two
EPCC. Power supplies, including the uninterruptible
different modes: isochronous and droop. The
power supplies (UPSs) and the console heaters, can also
isochronous mode is used to share the loading on
be monitored. The total output for the ac generation
generators and to keep a constant speed or frequency.
system is monitored for frequency, voltage, and current.
The amount of fuel to the diesel determines the load each
Individual bus ties can be monitored for current loads.
generator can carry. In the droop mode, the frequency
The operator uses the rotary switch on the EPCC to
will vary as the load is changed, but only within
select each bus tie.
predefine limits. This predefine area of droop is 0 to
The generator can be taken off the line if REMOTE
6 percent of the bus frequency. The operator can control
control is given to the EPCC and the generator switch is
the frequency of a generator manually from the front
turned to the TRIP position. The switch will work in the
panel of the EPCC. Using the increase/decrease knob
CLOSE position only if the paralleling mode switch is
will change the frequency higher or lower, when the
in the BYPASS or PERMISSIVE position and the
operator needs to match a generator to a bus to parallel
generator switch is at the BUS position. The
PERMISSIVE mode permits manual closure of the
The voltage regulator controls the generator output
breaker only when the automatic paralleling device
through the field excitation. The voltage can be
(APD) senses the generator is in synchronization with
controlled from the respective switchboards, except
the power bus. The BYPASS disables the APD so
switchboard No. 4. Switchboard No. 4 is in the same
synchronization has to be accomplished manually, The
space as the EPCC and has the MANUAL voltage
generator breaker is closed manually by the operator.
control on the EPCC panel. The manual preset
The load shed circuit breaker can be opened and
potentiometer on switchboard No. 4 at the EPCC gives
tripped by the EPCC operator when the EPCC is in the
the field excitation circuit a reference from which to
REMOTE mode. This circuit breaker can be either
work. The second mode is the AUTOMATIC mode. The
manually or automatically tripped. When an overload
voltage regulator AUTO ADJUST potentiometer on the
condition is sensed, the sensors from the generator bus
EPCC can raise or lower the voltage by controlling a
will trip all the load shed circuit breakers. This action
motorized potentiometer on the generator set. The
will remove the nonvital bus from the bus ring.
motorized potentiometer sets a limit for field excitation
The manual voltage control for the No. 4
and voltage output. If the voltage goes up, feedback
causes the field excitation to drop, bringing the voltage
switchboard is on the EPCC since the switchboard and
back into tolerance.
EPCC are both in the CCS. The No. 4 switchboard does