ABB REL 505-C1 2.3 Series - Measuring the Operate Value for the Zero Sequence Function

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Fuse failure supervision (FUSE) Chapter 10
Verifying settings by secondary
injection
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-sequence operating voltage.
8.3 Measuring the operate value for the zero sequence function
Measure the operate value for the zero 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 correspond-
ing zero-sequence voltage according to the equation.
Observe that the voltages in the equation are phasors.
(Equation 6)
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.
Where:
= the measured phase voltages
U
L1
U
L2
and U
L3
a1e
j
2 π⋅
3
--- --- - ----
⋅ 05 j
3
2
-------
+,–==
Where:
= the measured phase voltages.
3U
0
⋅ U
L1
U
L2
U
L3
++=
U
L1
, U
L2
and U
L3