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8.2
8.3
Fuse failure supervision (FUSE)
8.
Simultaneously establish normal voltage and current operating con-
ditions and observe the corresponding output signals.
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
Measuring the operate value for the
negative sequence function
Measure the operate value for the negative sequence 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.
Slowly decrease the measured voltage in one phase until the
FUSE-VTSU signal appears.
3.
Record the measured voltage and calculate the corresponding neg-
ative-sequence voltage according to the equation.
Observe that the voltages in the equation are phasors:
2
⋅
⋅
3 U
U
a
U
=
+
+
2
L 1
L 2
Where:
U
U
and
L1
L2
2 π
⋅
---------- -
j
3
⋅
,
a
=
1 e
=
–
0 5
+
j
4.
Compare the result with the set value (consider that the set value
3U2> is in percentage of the base voltage U1b) of the negative-se-
quence operating voltage.
Measuring the operate value for the zero sequence function
Measure the operate value for the zero sequence function, if included in the terminal.
⋅
a
U
L3
= the measured phase voltages
U
L3
3
------ -
2
Chapter 13
Verifying settings by secondary
injection
(Equation 1)
99
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