Siemens 6MD85, Manual

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You can define the characteristic curve as desired.
•
The pickup and dropout behaviors of this stage are determined by the standard parameter
Threshold
and, if necessary, by an additional parameter
Threshold (absolute)
.
User-Defined Characteristic Curve
With the user-defined characteristic curve, you can define the operate curve point by point using up to 30
value pairs of current and time. The device uses linear interpolation to calculate the characteristic curve from
these values. You can also define a dropout characteristic curve if you wish.
Pickup and Dropout Behaviors with the User-Defined Characteristic Curve
When the input variable exceeds the
Threshold
value by 1.1 times, the characteristic curve is processed. An
integrating method of measurement totalizes the weighted time. The weighted time results from the charac-
teristic curve. For this, the time that is associated with the present current value is determined from the char-
acteristic 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
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.
[dwocpken-140611-02.tif, 2, en_US]
Figure 7-70 Pickup Behavior and Dropout Behavior when Using a User-Defined Characteristic Curve
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i
NOTE
The currents that are lower than the current value of the smallest characteristic-curve point do not extend
the operate time. The pickup characteristic runs in parallel to the current axis up to the smallest character-
istic-curve point. Currents that are larger than the current value of the largest characteristic-curve point do
not reduce the operate time. The pickup characteristic runs in parallel to the current axis from the largest
characteristic-curve point.
If you want to change the pickup threshold of the stage without changing all points of the characteristic curve,
you can use the additional
Threshold (absolute)
parameter.
Protection and Automation Functions
7.4 Overcurrent Protection, Phases
SIPROTEC 5, High-Voltage Bay Controller, Manual 623
C53000-G5040-C015-9, Edition 11.2017