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Logic of the Advanced Stage
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Figure 7-82
Pickup and Dropout Behaviors of the Inverse-Time Characteristic Curve According to IEC and ANSI (Basic and
Advanced Stage)
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
SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017
Logic Diagram of the Inverse-Time Overcurrent Protection (Ground) – Advanced
Protection and Automation Functions
7.5 Overcurrent Protection, Ground
649
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