Shore power breaker control from the EPCC is
There is one SSGTG summary alarm LED for each
limited to sending a trip command to each breaker
SSGTG at the EPCC. The summary alarm lights for
simultaneously when the ALL CB OPEN pushbutton is
SSGTGs No. 1 and No. 2 operate when at least 1 of 22
depressed. All shore power close control and phase
alarm conditions occurs. The SSGTG No. 3 summary
m o n i t o r i n g devices are locally operated from
alarm light operates when at least 1 of 25 alarm
switchboard No. 2 in MER No. 2. When the shore power
conditions occur.
breakers are closed, circuits in each switchboard will
Any inputs to the EPCC not originating from the
automatically command each SSGTG governor to
SSGTG LOCOP are classified as direct. These direct
DROOP to prepare for a shift from ship's power to shore
inputs can be either discrete or analog. Direct discrete
power.
inputs are typically received from auxiliary contacts in
equipment controllers or contact switches associated
Circuit Breaker Operation
with the SSGTG support system. Direct analog inputs
The EPCC provides centralized control and
are received from the resistance temperature elements
monitoring of 3 generator circuit breakers, 6 bus tie
( R T E ) or tank level receivers associated with an
breakers, and 12 shore power breakers. The push-button
SSGTG.
indicators for these circuit breakers are located on the
EPCC mimic panel. Control of circuit breakers from the
Electrical Distribution Monitoring and Control
EPCC is enabled only when the LOCAL CONTROL
alarm light for a switchboard is extinguished.
An electrical switchboard has analog and discrete
EPCC operation of circuit breakers is accomplished
sensing devices for monitoring generator or bus output
through the same circuits used by the switchboard
and circuit breaker status. Alarm, status, and control
controls. Depressing an EPCC push-button indicator
information flows between the switchboard and the
energizes a 28-volt dc close or trip relay at the associated
EPCC. The EPCC receives this information in one of
switchboard. The 10-position synchronization
three ways:
C I R C U I T BREAKERS select switch and SYNC
1. Directly from potential transformers and current
MONITOR BYPASS push button enable operation of
transformers
the close circuit. When a relay is energized, a control
circuit in the breaker assembly energizes a close or open
2. Directly from circuit breakers
trip coil to execute the desired status change.
3. As discrete inputs from switchboard relay logic
circuits
Gas Turbine Control
The voltage and current signals from the current and
The gas turbine controls available at the EPCC
potential transformers are sent to transducers in the
consist of gas turbine start air selection, governor mode
EPCC to generate voltage, current, frequency, and
selection, and manual bleed air valve control. Also
power signals. These signals directly drive the power
available at the EPCC are gas turbine start and stop
generation and distribution and system output LED
c o n t r o l and gas turbine frequency control. These
meters. These signals are also sent to the computer for
o p e r a t o r interfaces provide discrete inputs to the
alarm generation and the PDU's demand display. The
LOCOP, which operates all SSGTG support systems
voltage displayed on the system output panel meter is
and gas turbine control elements.
selected by the position of the associated SOURCE
The availability of an SSGTG start from the EPCC
selector switch.
is a function of the LOCOP 301 sequencer "ready to
The electrical distribution system can be operated
s t a r t " discrete output, LOCOP LOCAL/REMOTE
manually from either the switchboard or the EPCC.
switch, and switchboard voltage regulator mode switch.
Automatic sequencing takes place in the switchboards
When the LOCOP is in REMOTE, the switchboard and
only when a fault condition exists. The EPCC does not
EPCC can start the SSGTG. When the switchboard
automatically control any circuit breakers as a part of
GTG START TRANSFER switch is in LOCAL, both
the standby generator start or any other function.
the EPCC and the switchboard can start the SSGTG.
S w i t c h b o a r d relay logic and LOCOP sequencer
W h e n the switchboard GTG START TRANSFER
" G e n e r a t o r Breaker Trip Command" are the only
switch is in REMOTE, only the EPCC can start the
SSGTG.
automatic breaker controls.
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