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8.4
100
Fuse failure supervision (FUSE)
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 corresponding ze-
ro-sequence voltage according to the equation.
Observe that the voltages in the equation are phasors.
⋅
3 U
U
U
U
=
+
+
0
L1
L2
L3
Where:
= the measured phase voltages.
U
, U
and U
L 1
L2
L 3
4.
Compare the result with the set value (consider that the set value
3U0> is in percentage of the base voltage U1b) of the zero-sequence
operating voltage.
Checking the operation of the du/dt, di/dt based function
Check the operation of the du/dt, di/dt based function, if included in the terminal.
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.
Connect the nominal dc voltage to the FUSE-CBCLOSED binary in-
put.
3.
Change the voltages and currents in all three phases simultanously.
The voltage change should be greater then set DU> and the current
change should be less than the set DI<.
•
The FUSE-VTSU and FUSE-VTSZ signals appear without any time
delay. If the remaining voltage levels are higher than the set U< of
the DLD function, only a pulse is achieved.
•
FUSE-VTF3PH should appear after 5 seconds, if the remaining volt-
age levels are lower than the set U< of the DLD function.
Chapter 13
Verifying settings by secondary
injection
(Equation 2)
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