
30 KENR8601
Systems Operation Section
4. The first generator set to energize VBR will initiate
the dead bus close sequence a nd will inhibit the
other generator set from closing to the dead bus.
If the first generator sets circuit breaker does not
close after 2 seconds, it will pass dead bus close
control to the second generator set. The second
generator set will inhibit the first generator set
from closing to the dead bus and attempt to close
its circuit breaker to the dead bus. If the second
generator sets circuit breaker does not close after
2 sec onds (field adjustable), it will pass dead bus
close control back to the first generator set. This
process continues until one of the generator sets
closes to the dead bus or the fail to parallel time
delay expires. Detailed e xplanation follows:
a. As the first generator set reaches 90% rated
speed and voltage, the VBR relay energizes.
The dead bus circuit confirms the bus is dead
through a DBR contact.
b. After a 0.25 second delay, the Dead Bus
Permissive Timer (DBPT) w ill close its contact,
energizing the Dead Bus Permissive Relay
(DBPR). When DBPR energizes in the first
generator set, the normally closed contact
wired to the second generator set opens,
preventing it from closing to the dead bus
c. After a 0.25 second delay, the DBTR energizes.
The contact from this relay is fed into the
GSC+P Auto Sync logic, starting the process
of an automatic dead bus closure.
d. If the circuit breaker does n ot close within 2
seconds, the Dead Bus Alternate Timing Relay
(DBATR) will energize, and stop the automatic
dead bus close sequence for the first generator
set. The second generator set will then begin
the automatic dead bus close sequence,
starting at step 4.babov e.
5. Before th e GSC+P will issue an automa tic dead
bus close command, the following conditions must
be met.
a. The D BTR must be energized.
b. Th e bus must be dea d, as indicated by the
DBR.
c. The System In Auto Relay (SIAR) must be
energized. The SIAR relay is energized when
the ECS and the PCS are both in auto, and the
Shutdown Relay (SDR) is not energized.
d. The generator sets circuit breaker is not
closed, as indicated by the Circuit Breaker
Relay (CBR).
e. The generator set has reached 90% rated
speed and voltage, as indicated b y the VBR.
f. The PCS is in AU TO.
6. Once the above conditions are m et, the GSC+P
will confirm the bus voltage is below the dead bus
voltage setpoint (P311) and will issue a breaker
close output comm and, activating the Circuit
Breaker Permissive Relay (CBPR).
7. A CBPR contact will energize the Circuit Breaker
Close Relay (CBCR).
8. A CBCR contact will energize the circuit breaker
close coil, automatically closing the circuit breaker.
Live Bus Close
1. For automatic synchronization, the ECS and PCS
must be in the AUTO position. The following
sequence of operations assumes the switches
are in these positions. Changing either of these
switch positions will interrupt the automatic mode
of operation and prevent the circuit breaker from
automatically closing.
2. When a source is present on the load bus, the
dead bus relay is energized, indicating the bus is
live. TheBus Transformer Box (BTB+) also detects
voltage present on the bus.
3. The GSC+P will actively adjust the generator set
frequency to automatically bring the generator
set voltage in phase with the bus voltage. The
GSC+P checks if there are phase sequence
alarms, inappropriate voltage alarms, or any other
alarm present.
a. Yes – The G SC+P will issue the appropriate
alarm. Breaker closure is prevented until the
fault is corrected.
b. No – The GSC+P will verify conditions for
synchronization and perform automatic
synchronizatio n.
4. When the output frequency is in phase with the
bus frequency and within the phase tolerance limit
(P305), the GSC+P will issue a breaker close
command, activating the CBPR.
5. A CBPR contact will energize the CBCR.
6. A CBCR contact will energize the circuit breaker
close coil, automatically closing the circuit breaker.
a. If the circuit breake r is not closed with in 45
seconds of receipt of remote start signal, the
fail to parallel a la rm will activate and initiate a
generator set shutdown.