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2 Functions
Zero Sequence
The zero sequence voltage time protection operates according to a voltage-depen-
Voltage Time Pro-
dent trip time characteristic. It can be used instead of the time overcurrent stage with
tection (U
-inverse)
inverse time delay.
0
The voltage/time characteristic can be displaced in voltage direction for a determined
constant voltage U0inv. minimum, valid for t→ ∞ and in time direction by a deter-
mined constant time T forw. (U0inv)). The characteristics are shown in the Tech-
nical Data.
Figure 2-91 shows the logic diagram. The tripping time depends on the level of the
zero sequence voltage U
increases towards the earth fault location. The inverse characteristic results in the
shortest command time for the relay closest to the fault. The other relays then reset.
Figure 2-91
Directional zero-sequence voltage time protection with non-directional backup stage
212
. For meshed earthed systems the zero sequence voltage
0
7SD5 Manual
C53000-G1176-C169-1
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