Basler Electric DGC-2020HD - Manual (Page 146)

136 9469300990 Rev B
Pickup and Trip
When the measured frequency decreases below (underfrequency protection) or increases above
(overfrequency protection) the frequency threshold established by the Pickup setting for three consecutive
sensing voltage cycles, a timer begins timing towards a trip.
Timer duration is established by the Activation Delay. An Activation Delay of zero (0) makes the 81
element instantaneous with no intentional time delay.
If an underfrequency or overfrequency pickup condition persists for the duration of the element Activation
Delay setting, the element Trip output becomes true. In BESTlogicPlus, the Trip output can be connected
to other logic elements or a physical relay output to annunciate the condition and initiate corrective action.
If the pickup condition subsides before the element activation delay expires, the timer is reset, no
corrective action is taken, and the element is rearmed for any other occurrences of underfrequency or
overfrequency.
Hysteresis
The hysteresis setting functions as an overfrequency/underfrequency dropout by preventing rapid
switching of the pickup output.
Per Unit
Settings which are related to machine ratings can be set in either actual units of hertz or in per unit
values. Per unit settings are available for Pickup (81O/81U) and Inhibit Voltage (81U). 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.
Conversely, 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 setting has native units of Frequency in Hz, and the rated data associated with it is Rated
Frequency (on the System Parameters, Rated Data screen).
•
Frequency 81-x Pickup
The following setting has native units of Secondary Volts, and the rated data associated with it is Rated
Secondary Volts (on the System Parameters, Rated Data screen).
•
Frequency 81-x Inhibit Voltage
Alternate Frequency Scale Factor
An alternate frequency scale factor setting is used for automatic adjustment of the frequency pickup
settings in applications that might utilize more than one operating frequency. For example, a machine that
is configurable between 50 or 60 Hz operation. The scale factor setting is implemented when the DGC-
2020HD senses a closure at a contact input that is connected to the Alternate Frequency Override logic
element in BESTlogicPlus programmable logic. When the Alternate Frequency Override is true, 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-2020HD and the scale factor setting is 2.000, the pickup setting will be doubled
(2.000 x PU).
Alarm Configuration
An underfrequency or overfrequency annunciation can be user-selected to trigger a pre-alarm (warning)
or alarm (shutdown). These can also be user-configured to close a programmable output.
Element status is available in BESTlogicPlus programmable logic when “Status Only” is selected.
Inhibit Voltage
Inhibit Voltage settings impede underfrequency element operation during undervoltage conditions that
may occur during equipment startup.
Generator Protection DGC-2020HD