Basler Electric DGC-2020 - Manual (Page 187)

stability is further controlled by two timers. Voltage conditions must meet the stability pickup and dropout
settings for the duration of the Bus Stable Activation Delay
R . Breaker closure is not considered if the
voltage conditions do not meet the stability pickup and dropout settings for the duration of the Bus Stable
Activation Delay setting. When the bus does not meet the voltage or frequency criteria for the Bus Stable
condition, the bus status is reported as Bus Failed (not stable and not dead) after the duration of the Bus
Failed Activation Delay
S .
The Bus Stable overvoltage and undervoltage detection elements have the low-line scale factor T applied
to them to enhance versatility for reconfigurable machines. When the low-line override is active, the
thresholds for the overvoltage and undervoltage detection are multiplied by the low-line scale factor. The
effect is that low-line threshold = element threshold setting x low-line scale factor.
An alternate frequency scale factor setting U 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-
2020 senses a contact 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-2020 and the scale factor setting is 2.000, the pickup setting will be doubled
(2.000 x PU).
Settings which are related to machine ratings can be set in either actual units of voltage or in per unit V
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 Primary Volts, and the rated data associated with them is
Rated Volts (on the System Parameters, Rated Data screen).
•
Dead Bus Threshold
•
Bus Stable Overvoltage Pickup
•
Bus Stable Overvoltage Dropout
•
Bus Stable Undervoltage Pickup
•
Bus Stable Undervoltage Dropout
The following settings have native units of Frequency in Hz, and the rated data associated with them is
Rated Frequency (on the System Parameters, Rated Data screen).
•
Bus Stable Overfrequency Pickup
•
Bus Stable Overfrequency Dropout
•
Bus Stable Underfrequency Pickup
•
Bus Stable Underfrequency Dropout
The BESTCOMSPlus Bus Condition Detection screen is illustrated in Figure 4-63.
NOTE
Voltage threshold and pickup settings on the Bus Condition Detection screen
are entered in primary values (generator side of VT).
9400200990 Rev X DGC-2020 BESTCOMSPlus
® Software
4-77