9400200990 Rev I DGC-2020 BESTCOMSPlus Software 4-43
D
Gen and Bus Stable Undervoltage Pickup and Dropout: Adjustable from 10 to 12,000 Vac in 1 Vac
increments.
E
Gen and Bus Stable Overfrequency Pickup and Dropout: Adjustable from 46 to 64 Hz in 0.05 Hz
increments for 50/60 Hz generator frequency (style number x1xxxxxxx).
F
Gen and Bus Stable Underfrequency Pickup and Dropout: Adjustable from 46 to 64 Hz in 0.05 Hz
increments for 50/60 Hz generator frequency (style number x1xxxxxxx).
G
Bus Stable Activation Delay: Adjustable from 0.1 to 600 in 1 second increments.
H
Bus Failed Activation Delay: Adjustable from 0.1 to 600 in 1 second increments.
Automatic Synchronizer (Optional)
Two methods of generator synchronization are offered: phase lock loop and anticipatory
A
. In both
methods, the DGC-2020 adjusts the frequency and voltage of the generator to match that of the bus
(mains) and then connects the generator to the bus by closing the breaker. Anticipatory mode has the
added capability of compensating for the breaker closing time (the delay between when a breaker close
command is issued and the breaker blades close). The DGC-2020 calculates the advance phase angle
that is required to compensate for the breaker closure time by monitoring the frequency difference
between the generator and the bus.
BESTCOMSPlus automatic synchronizer settings (DGC-2020, Breaker Management, Synchronizer) are
illustrated in
Figure 4-40.
Freq
uency Correction
Generator frequency correction is defined by the slip frequency setting and further refined by the breaker
closing angle setting. The slip frequency setting
B
establishes the maximum allowable deviation of the
generator speed (frequency) from the bus frequency. To minimize the impact on the bus during
synchronization, the Fgen>Fbus setting
C
can be enabled to force the generator frequency to exceed the
bus frequency at the moment of breaker closure. If this is the case, the DGC-2020 will drive the generator
frequency higher than the bus frequency before closing the breaker. The breaker closing angle setting
D
defines the maximum allowable phase angle difference between the generator and the bus. For breaker
closure to be considered, the slip angle must remain below this setting for the duration of the sync
activation delay setting
E
.
Voltage Correction
Generator voltage correction is defined by the regulation offset setting
F
. This setting, expressed as a
percentage of the bus voltage, determines the band of generator voltage surrounding the bus voltage
when breaker closure will be considered. If the Vgen>Vbus setting
G
is enabled, the DGC-2020 will drive
the generator voltage to be greater than the bus voltage by an amount equal to the regulation offset
setting divided by two.
Synchronization Failure
The maximum desired duration for synchronizing to take place is established by the sync fail activation
delay setting
H
. If synchronization (breaker closure) fails to occur within this time setting, generator
synchronization will be aborted and a failure will be annunciated. Note that if either bus goes unstable, the
synchronizer timers are reset.
NOTE
If the generator frequency is 400 Hz, the settings on the Synchronizer screen do
NOT apply. In this case, BESTCOMSPlus will not allow these settings to be
changed.
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