GE 889 - Offline Overcurrent (50 OFL)

CHAPTER 4: SETPOINTS PROTECTION
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–151
Offline Overcurrent
(50OFL)
The Offline Overcurrent feature is active only when the generator is in offline mode. In this
case, it is easier to differentiate between system faults and machine faults. When neutral
end CT bank measurements (Ia, Ib, Ic) are used, this element may be set to a much higher
sensitivity than the differential element in order to detect high impedance phase faults. In
the event of a low impedance fault, the differential elements still shutdown the generator
quickly.
NOTE
NOTE:
Since the breaker auxiliary contacts wired to the 889 Breaker Status Input may not operate
at exactly the same time as the main breaker contacts, the time delay should be
coordinated with the difference of the operation times.
Path: Setpoints > Protection > Group 1 > Generator > Offline Overcurrent
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
SIGNAL INPUT
Range: CT Bank 1 - J1, CT Bank 2 - K1
Default: CT Bank 1 - J1
NOTE
NOTE:
This setting is order code dependent. In the case of two CT cards, it is recommended that
the CT wired in the neutral end is selected as input for this function.
PICKUP
Range: 0.05 to 1.00 x CT in steps of 0.01
Default: 0.05 x CT
NOTE
NOTE:
If the unit auxiliary transformer is on the generator side of the breaker, the pickup level
must be set greater than the unit auxiliary load.
PICKUP DELAY
Range: 0.00 to 600.00 s in steps of 0.01 s
Default: 0.08 s
OUTPUT RELAY
Range: Do Not Operate, Operate
Default: Do Not Operate
..\Generator\OfflineOverCurrent
ItemName Value Unit
Function Disabled
SignalInput CTBank1ͲJ1
Pickup 0.05 xCT
PickupDelay 0.08 s
OutputRelay DoNotOperate
Block Off
Events Disabled
Targets SelfͲReset
OfLnOC