Basler Electric DGC-2020HD - Manual (Page 149)

9469300990 Rev B 139
The six, identical overcurrent elements are designated 51-1, 51-2, 51-3, 51-4, 51-5, and 51-6. Element
logic connections are made on the BESTlogicPlus screen in BESTCOMSPlus and element operational
settings are configured on the Overcurrent settings screen in BESTCOMSPlus.
BESTCOMSPlus Navigation Path: Settings Explorer, Generator Protection, Current, Overcurrent (51)
Front Panel Navigation Path: Settings Explorer > Protection > Settings Group x (where x = 0 to 3) >
Current Protection > Overcurrent (51)
Element Operation
Overcurrent protection can be used to protect equipment from damage caused by phase failure or
forward/reverse phase sequence.
Two sets of overcurrent settings are provided for each element: one for three-phase generator
connections and one for single-phase generator connections. The Pickup setting is entered based on the
CT secondary side (DGC-2020HD). When a single-phase override contact input is received, the DGC-
2020HD automatically switches from the three-phase overcurrent settings to the single-phase overcurrent
settings.
Modes of Protection
Eight modes of protection are available: IA, IB, IC, Imax, 3I0, I1, I2, and IG. Descriptions of the protection
modes in three-phase and single-phase systems are provided in Table 44.
Table 44. Modes of Protection
Mode Three-Phase Single-Phase
IA, IB, IC
Overcurrent protection elements include
three independent comparators and
timers, one for each phase. Mode
selection determines which phase pickup
is required to activate protection. Overcurrent protection elements include
three independent comparators and
timers, one for each phase. Mode
selection determines which phase pickup
is required to activate protection.
Imax
Imax mode provides overcurrent protection
in a three-phase system when any one
phase increases above the Pickup setting. Imax mode provides overcurrent protection
in a single-phase system when any one
phase increases above the Pickup setting.
3I0
3I0 mode provides neutral overcurrent
protection in a three-phase system. 3I0 mode is an invalid selection for a
single-phase system.
I1
I1 mode provides positive-sequence
overcurrent protection in a three-phase
system. I1 mode is an invalid selection for a single-
phase system.
I2
I2 mode provides negative-sequence
overcurrent protection in a three-phase
system. I2 mode is an invalid selection for a single-
phase system.
IG
IG mode provides ground fault protection
in a three-phase system. IG mode provides ground fault protection
in a single-phase system.
Source
A Source setting configures an overcurrent element to monitor the generator sensing input terminals or
the bus sensing input terminals.
Pickup and Trip
When the measured current increases above the current threshold established by the Pickup setting, a
timer begins timing towards a trip.
Timer duration is established by the Time Dial and Curve settings. A Time Dial of zero (0) makes the 51
element instantaneous with no intentional time delay.
DGC-2020HD Generator Protection