Basler Electric DGC-2020 - Manual (Page 186)

CAUTION
Use caution when connecting “dead” generators to a “dead” bus. Undesired
operation or system damage could occur if the bus becomes “live” while “dead”
generators are connected to it.
Before the DGC-2020 initiates a normal breaker closure (a stable generator is closed to a dead bus or
stable bus), the generator voltage must be stable. The DGC-2020 uses several settings to determine
voltage stability. These settings include pickup and dropout levels for overvoltage
C , undervoltage D ,
overfrequency E , and underfrequency F . Recognition of generator stability is further controlled by two timers.
Voltage conditions must meet the stability pickup and dropout settings for the duration of the Gen Stable
Activation Delay
G . Breaker closure is not considered if the voltage conditions do not meet the stability
pickup and dropout settings for the duration of the Gen Stable Activation Delay setting. When the
generator does not meet the voltage or frequency criteria for the Gen Stable condition, the generator
status is reported as Gen Failed (not stable and not dead) after the duration of the Gen Failed Activation
Delay
H .
The Gen Stable overvoltage and undervoltage detection elements have the low-line scale factor I 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 J 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 voltage or in per unit K
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 Gen Threshold
•
Gen Stable Overvoltage Pickup
•
Gen Stable Overvoltage Dropout
•
Gen Stable Undervoltage Pickup
•
Gen 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).
•
Gen Stable Overfrequency Pickup
•
Gen Stable Overfrequency Dropout
•
Gen Stable Underfrequency Pickup
•
Gen Stable Underfrequency Dropout
Bus Sensing
Dead bus detection is controlled by a Dead Bus Threshold setting L and a Dead Bus Activation Delay
setting M . A dead bus is recognized when the voltage of all phases decreases below the threshold setting
for the duration of the time delay setting.
Before the DGC-2020 initiates a breaker closure to a bus that is not dead, the voltage must be stable.
The DGC-2020 uses several settings to determine voltage stability. These settings include pickup and
dropout levels for overvoltage
N , undervoltage O , overfrequency P , and underfrequency Q . Recognition of bus
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® Software
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