Siemens siprotec 7SA6 User Manual page 287

Inverse Time
Overcurrent Stage
with Inverse
Logarithmic
Characteristic
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Forward
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forwards
direction-
reverse
determination
Figure 6-63 Logic diagram of the 3I
Zero Sequence
Voltage Time
Protection
(U -Inverse)
0
7SA6 Manual
C53000-G1176-C133-1
The inverse logarithmic characteristic differs from the other inverse characteristics
mainly by the fact that the shape of the curve can be influenced by a number of
parameters. The slope ,S 7LPH 'LDO and a time shift 7 ,3PD[ which directly
affect the curve, can be changed. The curves are illustrated in the technical date in
Section 10.5, Figure 10-4.
The logic diagram is shown in Figure 6-63. In addition to the curve parameters, a
minimum time ,S 0LQ7'(/$< can be determined; below this time no tripping can
occur. Below a current factor of ,S 6WDUWSRLQW, which is set as a multiple of the
basic setting ,S 3,&.83, no tripping can take place.
Further information regarding the effect of the various parameters can be found in the
setting information of the function parameters in Sub-section 6.5.2, refer also to Figure
6-68.
The remaining setting options are the same as for the other curves.
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&
permissive
teleprot..
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≥1
&
&
switch on
to fault
–stage for the inverse logarithmic curve
0P
The zero sequence voltage time protection operates according to a voltage-
dependent trip time characteristic. It can be used instead of an inverse time
overcurrent stage.
The voltage/time characteristic can be displaced in voltage direction for a determined
constant voltage (8LQY PLQLPXP, valid for t → ∞) and in time direction by a
determined constant time (7 IRUZ 8LQY ). The different characteristics and their
underlying formulae are shown in the Technical Data Section (10.5, Figure 10-5).
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Functions
EF 3I0p TRIP
1369
6-105