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Fuse failure supervision (FUSE) Chapter 10
Verifying settings by secondary
injection
5. Disconnect the dc voltage from the FUSE-MCB binary input
terminal.
6. Disconnect one of the phase voltages and observe the logical
output signals on the terminal binary outputs.
FUSE-VTSU and FUSE-VTSZ signals should simultaneously ap-
pear.
7. After more than 5 seconds disconnect the remaining two
phase voltages and all three currents.
• There should be no change in the high status of the output signals
FUSE-VTSU and FUSE-VTSZ.
• The signal FUSE-VTF3PH will appear.
8. Simultaneously establish normal voltage and current operat-
ing conditions and observe the corresponding output sig-
nals.
They should change to the logical 0 as follows:
• Signal FUSE-VTF3PH after about 25 ms
• Signal FUSE-VTSU after about 50 ms
• Signal FUSE-VTSZ after about 200 ms
8.2 Measuring the operate value for the
negative sequence function
Measure the operate value for the negative sequence function, if included in the termi-
nal.
Procedure
1. Simulate normal operating conditions with the three-phase
currents in phase with their corresponding phase voltages
and with all of them equal to their rated values.
2. Slowly decrease the measured voltage in one phase until the
FUSE-VTSU signal appears.
3. Record the measured voltage and calculate the correspond-
ing negative-sequence voltage according to the equation.
Observe that the voltages in the equation are phasors:
(Equation 5)
3U
2
⋅ U
L1
a
2
U
L2
a+⋅ U
L3
⋅+=
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