Stage with Inverse-Time Characteristic Curve
Description
Logic of the Stage
[lodefocp-270612-01.tif, 1, en_US]
Figure 7-124
Logic Diagram of the Inverse-Time Overcurrent Protection (1-Phase)
Pickup and Dropout Behaviors of the Inverse-Time Characteristic Curve According to IEC and ANSI
When the input variable exceeds the threshold value by a factor of 1.1, the inverse-time characteristic curve is
processed. An integrating method of measurement totalizes the weighted time. The weighted time results
from the characteristic curve. For this, the time that is associated with the present current value is determined
from the characteristic curve. Once the weighted time exceeds the value 1, the stage operates.
When the measured value falls short of the pickup value by a factor of 1.045 (0.95 x 1.1 x threshold value),
the dropout is started. The pickup will be indicated as clearing. You can influence the dropout behavior via
setting parameters. You can select between instantaneous dropout (totalized time is deleted) or dropout
according to the characteristic curve (reduction of totalized time depending on the characteristic curve). The
7.8.4
7.8.4.1
Protection and Automation Functions
7.8 Overcurrent Protection, 1-Phase
752 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017
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