GE 489 - Manual (Page 79)

GE Multilin 489 Generator Management Relay 4-29
4 SETPOINTS 4.6 S5 CURRENT ELEMENTS
4
4.6.7 GROUND OVERCURRENT
PATH: SETPOINTS ÖØ S5 CURRENT ELEMENTS ÖØ GROUND O/C
The 489 ground overcurrent feature consists of both an alarm and a trip element. The magnitude of measured ground cur-
rent is used to time out against the definite time alarm or inverse time curve trip. The 489 inverse time curve for this element
may be either ANSI, IEC, or GE Type IAC standard curve shapes. This allows for simplified coordination with downstream
devices. If however, none of these curves shapes is adequate, the FlexCurve™ may be used to customize the inverse time
curve characteristics. If the Ground CT is selected as "None", the ground overcurrent protection is disabled.
The pickup level for the ground current elements is programmable as a multiple of the CT. The 50:0.025 CT
is intended for very sensitive detection of ground faults and its nominal CT rating for the 489 is 50:0.025.
For example, if the ground CT is 50:0.025, a pickup of 0.20 would be 0.20 × 5 = 1 A primary. If the ground CT is 50:0.025, a
pickup of 0.05 would be 0.05 × 5 = 0.25 A primary.
„ GROUND O/C
„ [ENTER] for more
GROUND OVERCURRENT
ALARM: Off
Range: Off, Latched, Unlatched
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to 5
GROUND O/C ALARM
PICKUP: 0.20 x CT
Range: 0.05 to 20.00 × CT in steps of 0.01
GROUND O/C ALARM
DELAY: 0 cycles
Range: 0 to 100 cycles in steps of 1
GROUND OVERCURRENT
ALARM EVENTS: Off
Range: On, Off
GROUND OVERCURRENT
TRIP: Off
Range: Off, Latched, Unlatched
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to 4
GROUND O/C TRIP
PICKUP: 0.20 x CT
Range: 0.05 to 20.00 × CT in steps of 0.01
CURVE SHAPE:
ANSI Extremely Inv.
Range: see Table 4–1: 489 Overcurrent Curve Types on
page 4–21.
FLEXCURVE TRIP TIME
AT 1.03 x PU: 65535 ms
Range: 0 to 65535 ms
Seen only if CURVE SHAPE is Flexcurve
FLEXCURVE TRIP TIME
AT 1.05 x PU: 65535 ms
Range: 0 to 65535 ms
Seen only if CURVE SHAPE is Flexcurve
↓
FLEXCURVE TRIP TIME
AT 20.0 x PU: 65535 ms
Range: 0 to 65535 ms
Seen only if CURVE SHAPE is set to Flexcurve
OVERCURRENT CURVE
MULTIPLIER: 1.00
Range: 0.00 to 1000.00 in steps of 0.01
OVERCURRENT CURVE
RESET: Instantaneous
Range: Instantaneous, Linear
ENTER
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