Siemens SIPROTEC 4 7UT6 Series Manual page 162

Functions
2.5 Time Overcurrent Protection for Earth Current
[logikdia-hochstromstufe-ie-fuer-erdstrom-121102-st, 1, en_GB]
Figure 2-80
The current detected at the assigned one-phase current measuring input is additionally compared with setting
value IE>. An annunciation is generated if the value is exceeded. If inrush restraint is used, a frequency anal-
ysis is performed first. If an inrush condition is detected, pickup annunciation is suppressed and an inrush
message is output instead. If there is no inrush or if inrush restraint is disabled, a tripping command will be
output after expiration of delay time T IE>. If inrush restraint is enabled and inrush current is detected, there
will be no tripping. Nevertheless, an annunciation is generated indicating that the time expired. The dropout
value is roughly equal to 95% of the pickup value for currents Ι > 0,3 · Ι
The following figure shows the logic diagram of the overcurrent stage IE>.
The pickup values for each of the stages IE> and IE>> and the delay times can be set individually.
162
Logic diagram of the high-current stage IE>> for earth current (simplified)
.
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SIPROTEC 4, 7UT6x, Manual
C53000-G1176-C230-5, Edition 09.2016