Logic
[lo_sensitive ground-current protection 3I0, 2, en_US]
Figure 6-144
Logic Diagram of the Non-Directional 3I0 Stage
Measured Value 3I0
The function usually evaluates the sensitively measured ground current 3I0 via a core balance current trans-
former. Since the linearity range of the sensitive measuring input ends at approx. 1.6 A, for larger secondary
ground currents, the function switches to the 3I0 current calculated from the phase currents. This results in a
very large linearity and settings range.
Depending on the connection type of the measuring point as well as the current terminal blocks used,
different linearity and setting ranges result. You can find more information in section Measured Value 3I0,
Method of Measurement , Page 569.
Method of Measurement
You use the Method of measurement parameter to define whether the stage uses the fundamental
comp. or the calculated RMS value.
•
Measurement of the fundamental component:
This method of measurement processes the sampled current values and filters out the fundamental
component numerically.
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
SIPROTEC 5, Overcurrent Protection, Manual 613
C53000-G5040-C017-8, Edition 07.2017
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