GE T60 Instruction Manual page 452

5.7 CONTROL ELEMENTS
f) VT FUSE FAILURE

PATH: SETTINGS CONTROL ELEMENTS
 VT FUSE FAILURE 1

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
are distance, voltage restrained overcurrent, and directional current.
There are two classes of fuse failure that occur:
• Class A: loss of one or two phases.
• Class B: loss of all three phases.
Different means of detection are 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. Also rapid decrease in the phase voltages magnitude from a healthy
voltage level without disturbance in current can indicate a VT fuse fail conditions. These noted indications of fuse failure
can also be present when faults are present on the system, so a means of detecting faults and inhibiting fuse failure decla-
5
rations during these events is provided.
Once the fuse failure condition is declared, it is 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
VT FUSE FAILURE 1 FUNCTION
The
VT NEU WIRE OPEN 1 FUNCTION
VT is connected in Delta, do not enabled this function because there is no neutral wire for Delta connected VT.
The
VT NEU WIRE OPEN 1 3 HRAM PKP
WIRE OPEN detection logic to pick up.
5-306

MONITORING ELEMENTS
VT FUSE FAILURE 1
FUNCTION: Disabled
 NEUTRAL WIRE OPEN 1
MESSAGE
 DETECTION: Disabled
 NEUTRAL WIRE OPEN 1
MESSAGE
 3 HARM PKP: 0.100
setting enables and disables the fuse failure feature for Source 1 VT Fuse Fail.
setting enables and disables the VT neutral wire open detection function. When the
setting specifies the pickup level of 3rd harmonic of 3V0 signal for the VT NEU
T60 Transformer Protection System

VT FUSE FAILURE 1(6)
Range: Disabled, Enabled
Range: Disabled, Enabled
Range: 0.000 to 3.000 pu in steps of 0.001
5 SETTINGS
input)
BLOCK
GE Multilin