Basler Electric DGC-2020ES - Manual (Page 63)

9469200990 Rev C 55
Generator Protection
DGC-2020ES controllers offer standard protection consisting of undervoltage (27), overvoltage (59),
overcurrent (50), overfrequency (81O), underfrequency (81U), and phase-imbalance voltage (47)
elements.
The description of generator protection is organized as follows:
•
Voltage (27, 59, 47)
•
Frequency (81)
•
Overcurrent (50)
Voltage
Voltage protection consists of an undervoltage element, an overvoltage element, and a phase-sequence
voltage element.
Undervoltage (27)
Two sets of undervoltage settings are provided for this element: one for three-phase generator
connections and one for single-phase generator connections. The pickup setting entered is based on the
PT secondary side. When a single-phase override contact input is received, the DGC-2020ES
automatically switches from the three-phase undervoltage settings to the single-phase undervoltage
settings.
An undervoltage condition is annunciated when the average of the three-phase (three-phase mode) or
the line-to-line voltage (single-phase mode) decreases below the corresponding 27 pickup setting for the
duration of the corresponding 27 activation delay. An undervoltage annunciation can be user-selected to
trigger a pre-alarm (warning) or alarm (shutdown). An undervoltage annunciation can also be user-
configured to close a programmable output.
The hysteresis setting functions as an undervoltage dropout by preventing rapid switching of the pickup
output.
A frequency-based inhibit setting prevents a 27 trip from occurring during an undervoltage condition
associated with system startup.
A low-line scale factor setting is used to automatically adjust the undervoltage pickup settings in
applications that may utilize more than one type of genset connection. The scale factor setting is
implemented when the DGC-2020ES senses a contact closure at a contact input programmed to activate
low-line override. This triggers 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-2020ES and the scale factor setting is 2.000, the pickup setting will be doubled (2.000
× PU).
The element is disabled when Alarm Configuration is set to “None”. Element status is available in
BESTlogic™Plus Programmable Logic when “Status Only” is selected.
Settings which are related to machine ratings can be set in either actual units of voltage or in per unit
values. When a native unit is edited, BESTCOMSPlus
® automatically recalculates the per unit value
based on the native unit setting and the rated data parameter (on the System Parameters, Rated Data
screen) associated with it. When a per unit value is edited, BESTCOMSPlus automatically recalculates
the native value based on the per unit setting and the rated data parameter associated with it.
Once all per unit values are assigned, if the rated data parameters are changed, BESTCOMSPlus
automatically recalculates all native unit settings based on the modified rated data parameters.
The following settings have native units of Secondary Volts, and the rated data associated with them is
Rated Secondary Volts (on the System Parameters, Rated Data screen).
•
Undervoltage 27 Three-Phase Pickup
•
Undervoltage 27 Single-Phase Pickup
DGC-2020ES Generator Protection