Vt Fuse Failure - GE UR Series Instruction Manual

5 SETTINGS
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PATH: SETTINGS CONTROL ELEMENTS
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VT FUSE FAILURE

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Every signal source includes a fuse failure scheme.
The VT fuse failure detector can be used to raise an alarm and/or block elements that may operate incorrectly for a full or
partial loss of AC potential caused by one or more blown fuses. Some elements that might be blocked (via the BLOCK
input) are distance, voltage restrained overcurrent, and directional current.
There are two classes of fuse failure that may occur: (A) loss of one or two phases, and (B) loss of all three phases. A dif-
ferent means of detection is required for each class. An indication of class A failures is a significant level of negative
sequence voltage, whereas an indication of class B failures is when positive sequence current is present and there is an
insignificant amount of positive sequence voltage. These noted indications of fuse failure could also be present when faults
are present on the system, so a means of detecting faults and inhibiting fuse failure declarations during these events is pro-
vided. Once the fuse failure condition is declared, it will be sealed-in until the cause that generated it disappears.
An additional condition is introduced to inhibit a fuse failure declaration when the monitored circuit is de-energized; positive
sequence voltage and current are both below threshold levels.
The common FUNCTION setting will Enable/Disable the fuse failure feature for all 6 sources.
SETTING
VT FUSE FAILURE
FUNCTION:
Disabled=0
Enabled=1
SOURCE 1
V_2
V_1
I_1
FLEXLOGIC OPERAND
SRC1 50DD OP
GE Power Management
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MONITORING ELEMENTS
VT FUSE FAILURE
FUNCTION: Disabled
COMPARATORS
RUN
V_2 > 0.25 p.u.
RUN
OR
V_1 < 0.05 p.u.
AND
RUN
I_1 > 0.075 p.u.
RUN
V_1 < 0.7 p.u. 0
AND
RUN
I_1 < 0.05 p.u.
Figure 5–77: VT FUSE FAIL SCHEME LOGIC
L90 Line Differential Relay
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VT FUSE FAILURE
Range: Disabled, Enabled
AND
20 CYCLES
OR
AND
AND
OR
AND
5.6 CONTROL ELEMENTS
5.6.11 VT FUSE FAILURE
FLEXLOGIC OPERAND
FUSE FAIL
SRC1 VT FUSE F OP
SRC1 VT FUSE F DPO
FAULT
827093A5.CDR
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