User-Defined Characteristic Curve
With the directional, 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 User-Defined Characteristic Curves
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 char-
acteristic 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 threshold value by a factor of 1.045 (0.95 × 1.1× threshold value),
the dropout is started. The pickup will be indicated as outgoing. 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 started from 0.9 of the set threshold value.
The following figure shows the pickup behavior and dropout behavior when a directional user-defined charac-
teristic curve is used.
[dwpidrbe-300913, 1, en_US]
Figure 7-120
Pickup and Dropout Behaviors when Using a User-Defined Characteristic Curve
i
i
NOTE
Note that 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
characteristic-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.
Application and Setting Notes
This stage is structured in the same way as the Inverse-time overcurrent protection – advanced stage. The
only difference is that you can define the characteristic curve as required. This section only provides applica-
tion and setting notes for setting the characteristic curves. For guidance on the other parameters of the stage,
see chapter
7.7.6.2 Application and Setting Notes
.
7.7.9.2
Protection and Automation Functions
7.7 Directional Overcurrent Protection, Ground
SIPROTEC 5, High-Voltage Bay Controller, Manual
741
C53000-G5040-C015-9, Edition 11.2017
Summary of Contents for 6MD85
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