4-34 DGC-2020 BESTCOMSPlus Software 9400200990 Rev I
The hysteresis setting
D
functions as an undervoltage dropout by preventing rapid switching of the pickup
output.
A frequency-based inhibit setting
E
prevents a 27 trip from occurring during an undervoltage condition
associated with system startup.
A low-line scale factor setting
F
is used to automatically adjust the undervoltage pickup settings in
applications that may utilize more than one type of genset connections. The scale factor setting is
implemented when the DGC-2020 senses a contact closure at a contact input programmed to activate
scaling of the protection settings. The value of the scale factor setting serves as a multiplier for the pickup
settings. For example, if a scale factor contact input is received by the DGC-2020 and the scale factor
setting is 2.000, the pickup setting will be doubled (2.000 × PU).
BESTCOMSPlus voltage protection settings (DGC-2020, Generator Protection, Voltage, Undervoltage)
are illustrated in
Figure 4-30. The 27-1 element is shown.
Figure 4-30. Undervoltage Protection Settings
A
Pickup: Adjustable from 70 to 576 Vac in 1 Vac increments.
B
Activation Delay: Adjustable from 0 to 30 s in 0.1 s increments.
C
Alarm Configuration: None, Alarm, or Prealarm.
D
Hysteresis: Adjustable from 1 to 60 Vac in 1 Vac increments.
E
Inhibit Frequency: Adjustable from 20 to 400 Hz in 1 Hz increments.
F
Low Line Scale Factor: Adjustable from 0 to 3.000 in increments of 0.001.
Overvoltage (59-1, 59-2)
Two sets of overvoltage settings are provided for each element: one for three-phase generator
connections and one for single-phase generator connections. The pickup setting entered is based on the
VT secondary side (DGC-2020). When a single-phase override contact input is received, the DGC-2020
automatically switches from the three-phase overvoltage settings to the single-phase overvoltage
settings.
An overvoltage condition is annunciated when the average of the three-phase (three-phase mode) or the
line-to-line voltage (single-phase mode) increases above the corresponding 59 pickup setting
A
for the
duration of the corresponding 59 activation delay
B
. An overvoltage annunciation can be user-selected to
trigger a pre-alarm
C
(warning) or alarm
C
(shutdown). An overvoltage annunciation can also be user-
configured to close a programmable output.
The hysteresis setting
D
functions as an undervoltage dropout by preventing rapid switching of the pickup
output.
A low-line scale factor setting
E
is used to automatically adjust the overvoltage pickup settings in
applications that may utilize more than one type of genset connections. The scale factor setting is
implemented when the DGC-2020 senses a contact closure at a contact input programmed to activate
scaling of the protection settings. The value of the scale factor setting serves as a multiplier for the pickup
settings. For example, if a scale factor contact input is received by the DGC-2020 and the scale factor
setting is 2.000, the pickup setting will be doubled (2.000 × PU).
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