Application And Setting Notes - Siemens 7SJ82 Manual

Protection and Automation Functions
6.12 Overcurrent Protection, 1-Phase
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Figure 6-103
Method of Measurement, Pickup and Dropout Behaviors of the Fast Stage
This stage evaluates the unfiltered measurands. Thus, very short response times are possible. When the abso-
lute values of 2 consecutive sampled values of the last half period exceed the Threshold, the stage picks up.
When all sampled values of the previous period are less than the dropout threshold, the stage drops out.
Blocking of the Stage
The picked up stage can reset completely via the binary input signal
6.12.6.2

Application and Setting Notes

Parameter: Threshold, Operate delay
•
Default setting (_:3) Threshold = 10.00 A
•
Default setting (_:6) Operate delay = 0.00 s
Set the Threshold and Operate delay parameters for the specific application.
Ensure that the sampled values are compared directly without an additional factor with the set threshold
value.
Parameter: Dropout ratio
•
Recommended setting value (_:4) Dropout ratio = 0.90
The recommended setting value of 0.90 is sufficient for many applications. To obtain high-precision measure-
ments, the Dropout ratio can be reduced. If you expect highly fluctuating measurands at the pickup
threshold, you can increase the Dropout ratio setting. This avoids chattering of the tripping stage.
534
Logic Diagram of the Fast Stage, 1-Phase
>Block stage .
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017