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GE Multilin 489 Generator Management Relay 4-71
4 SETPOINTS 4.11 S10 MONITORING
4
4.11.4 VT FUSE FAILURE
PATH: SETPOINTS ÖØ S10 MONITORING ÖØ VT FUSE FAILURE
A fuse failure is detected when there are significant levels of negative sequence voltage without corresponding levels of
negative sequence current measured at the output CTs. Also, if the generator is online and there is not significant positive
sequence voltage, it could indicate that all VT fuses have been pulled or the VTs are racked out. If the alarm is enabled and
a VT fuse failure detected, elements that could nuisance operation are blocked and an alarm occurs. These blocked ele-
ments include voltage restraint for the phase overcurrent, undervoltage, phase reversal, and all power elements.
Figure 4–20: VT FUSE FAILURE LOGIC
VT FUSE FAILURE
[ENTER] for more
VT FUSE FAILURE
ALARM: Off
Range: Off, Latched, Unlatched
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to 5
VT FUSE FAILURE
ALARM EVENTS: Off
Range: On, Off
ENTER
ESCAPE
ð
ð
MESSAGE
ESCAPE
MESSAGE
ESCAPE
99ms
99ms
Block
Appropriate
Elements
&
Operate
Alarm
Relay
I/I<20%
2 1
V / V > 25%
2 1
I>0.075 x CT
1
V > 0.05 xFull Scale
1
Breaker Status = Online
V < 0.05 Full Scale
1
×
0
0
AND
OR
AND