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.
You can set the Threshold (absolute) parameter to be greater than 1.1 times the Threshold value.
Then the stage behaviors are as follows:
•
The stage picks up when the measured current value exceeds the Threshold (absolute) value.
•
The stage starts dropout when the measured current value falls short of the Threshold (absolute)
value by 0.95 times.
•
For measured current values lower than the Threshold (absolute) value, no pickup takes place and
consequently the characteristic curve is not processed.
If you set the Threshold (absolute) parameter to be less than 1.1 times the Threshold value, the
pickup and dropout behaviors are not affected by the Threshold (absolute) parameter.
Application and Setting Notes
This stage is structured the same way as the Inverse-time overcurrent protection – advanced stage. The
only differences are described in chapter 6.3.6.1 Description . This chapter provides only the application and
setting notes for setting characteristic curves and for setting the Threshold (absolute) parameter. You
can find more information on the other parameters of the stage in chapter 6.3.5.2 Application and Setting
Notes .
Parameter: Current/time value pairs (from the operate curve)
With these settings, you define the characteristic curve. Set a current/time value pair for each characteristic-
curve point. The setting depends on the characteristic curve you want to realize.
Set the current value as a multiple of the threshold value. Siemens recommends that you set the Threshold
parameter to 1.00 in order to obtain a simple relation. You can change the threshold value setting afterwards
if you want to shift the characteristic curve.
Set the time value in seconds. The characteristic curve is shifted via the Time dial parameter.
NOTE
The value pairs must be entered in continuous order.
Parameter: Time dial
•
Default setting (_:101) Time dial = 1
With the Time dial parameter, you displace the characteristic curve in the time direction.
The set value for the Time dial parameter is derived from the time-grading schedule that has been prepared
for the electrical power system. Where no time grading and therefore no displacement of the characteristic
curve is required, leave the Time dial parameter at 1.
Parameter: Reset
•
Default setting (_:110) Reset = disk emulation
With the Reset parameter, you define whether the stage drops out according to the dropout characteristic
curve (in accordance with the behavior of a disk emulation = rotor disk) or instantaneously.
6.3.6.2
Protection and Automation Functions
6.3 Overcurrent Protection, Phases
350 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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