Basler Electric DGC-2020HD - Manual (Page 142)

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Source
A Source setting configures the phase voltage imbalance element to monitor the generator sensing input
terminals or the bus sensing input terminals.
Pickup and Trip
When the difference between any of the three phases of generator voltage increases above the threshold
established by the Pickup setting, a timer begins timing towards a trip.
Timer duration is established by the Activation Delay. An Activation Delay of zero (0) makes the 47
element instantaneous with no intentional time delay.
If a phase voltage imbalance 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 phase voltage
imbalance.
Hysteresis
The hysteresis setting functions as a phase voltage imbalance 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 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. 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 Secondary Volts, and the rated data associated with it is Rated
Secondary Volts (on the System Parameters, Rated Data screen).
•
Phase Imbalance 47-x Pickup
Low-Line Scale Factor
A low-line scale factor setting is used to automatically adjust the phase voltage imbalance pickup settings
in applications that might utilize more than one type of genset connection. The scale factor setting is
implemented when the DGC-2020HD is determined to be in a low-line configuration. If the Low-Line
Override function is assigned to a contact input via the Programmable Functions screen, the state of the
contact input and the detected configuration are ORed. This means, if one or both are true, then the
system is determined to be configured for low-line. 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-
2020HD and the scale factor setting is 2.000, the pickup setting will be doubled (2.000 x PU).
Alarm Configuration
Phase voltage imbalance annunciation can be user-selected to trigger a pre-alarm (warning) or alarm
(shutdown). It can also be user-configured to close a programmable output.
Element status is available in BESTlogicPlus programmable logic when “Status Only” is selected.
Logic Connections
Phase voltage imbalance element logic connections are made on the BESTlogicPlus screen in
BESTCOMSPlus. The phase voltage imbalance element logic block is illustrated in Figure 71. When the
Generator Protection DGC-2020HD