Vt Fuse Failure - GE Multilin 489 Instruction Manual

5.11.4 VT Fuse Failure

VT FUSE
FAILURE
5–92
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PATH: SETPOINTS S10 MONITORING
[ ] VT FUSE FAILURE
ALARM: Off
ASSIGN ALARM
MESSAGE
RELAYS (2-5): ---5
VT FUSE FAILURE
MESSAGE
ALARM EVENTS: Off
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 elements include voltage restraint for the
phase overcurrent, undervoltage, phase reversal, and all power elements.
I / I < 20%
2 1
V / V > 25%
2 1
I > 0.075 x CT
1
V > 0.05 x Full Scale
1
Breaker Status = Online
AN
×
V < 0.05 Full Scale
1
VT FUSE FAILURE
Range: Off, Latched, Unlatched
Range: Any combination of Relays 2 to
Range: On, Off
99ms
AN
0
99ms
0
FIGURE 5–26: VT Fuse Failure Logic
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
5
Block
Appropriate
Elements
&
Operate
Alarm
Relay