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.
I0 Elimination (Advanced Stage)
In order to increase the sensitivity for the 2-phase short circuit on the transformer low-voltage side, use the
I0 elimination of the phase currents for the overcurrent-protection application on one transformer.
In order to determine the I0 elimination of the phase currents, the transformer neutral point current I
Y
must be
measured.
[dwsgaocp-230414-01, 1, en_US]
Figure 6-11 I0 Elimination Principle
The transformer neutral point current I
Y
is measured via a 1-phase current measuring point that is connected
to the Voltage/current 1-phase. The function group Voltage/current 1-phase must be connected to the func-
tion group Voltage/current 3-phase in which the function Overcurrent protection, phases is being used.
[sccpfoint-230414-01, 1, en_US]
Figure 6-12 Connection of the Voltage/Current 1-Phase Function Group with the Neutral Point Input of the
Voltage/Current 3-Phase Function Group
In case of an I0 elimination, the following calculations result:
I
A-elim.
= I
A
- 1/3 I
Y
I
B-elim.
= I
B
- 1/3 I
Y
I
C-elim.
= I
C
- 1/3 I
Y
The phase current
I
phx-elim.
is necessary for the following protection process.
If the Method of measurement parameter is set to fundamental comp., the I0 elimination is applied.
The currents I
phx-elim.
are available as functional values.
Pickup delay (Advanced Stage)
If the current exceeds the threshold value, the pickup delay is generated. If the threshold remains exceeded
during the pickup delay time, the pickup signal is generated.
Protection and Automation Functions
6.3 Overcurrent Protection, Phases
SIPROTEC 5, Overcurrent Protection, Manual 331
C53000-G5040-C017-8, Edition 07.2017
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