RMS-Value Selection (Advanced Stage)
If RMS value is selected as the method of measurement, the protection function supports 2 kinds of RMS
measurement.
•
Normal RMS value
•
Gained RMS value from the function block Filter
If the function block Filter is configured and if you have enabled the filter, the gained RMS value is automati-
cally used.
NOTE
When the function block Filter is applied, only one 3-phase current measuring point is allowed to be
connected to the 3-phase current interface of the function group.
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 summarizes 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 below 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 dropout
according to characteristic curve (disk emulation) is the same as turning back a rotor disk. The weighted
reduction of the time is initiated from 0.9 of the set threshold value.
The characteristic curve and associated formulas are shown in the Technical Data.
Minimum Time of the Curve (Advanced Stage)
With the parameter Min. time of the curve, you define a minimum operate delay time. The operate
delay time of inverse-time characteristic curve never falls below the minimum operate delay time.
[DwOcp3Mi_20140715-01, 1, en_US]
Figure 7-68 Minimum Operating Time of the Curve
Protection and Automation Functions
7.4 Overcurrent Protection, Phases
SIPROTEC 5, High-Voltage Bay Controller, Manual 615
C53000-G5040-C015-9, Edition 11.2017
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