3-Phase Measuring-Voltage Failure
Logic
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Figure 9-7
Logic Diagram 3-Phase Measuring-Voltage Failure
Balanced Fault – VA, VB, VC <
A 3-phase measuring-voltage failure is detected if the following criteria are fulfilled simultaneously:
•
All 3 phase-to-ground voltages drop below the threshold value 3ph.fail. - VA,VB,VC <
•
A jump of the voltage (Signal jump V)
If these criteria are fulfilled and the monitoring is released and not blocked, the 3ph.failure-alarm indica-
tion is output. When the voltage returns (even as 1-phase), the monitoring drops out.
Release by Phase Current
When all phase currents exceed the threshold value 3ph.fail. - phs.curr.release the monitoring is
released.
Blocking in the Case of a System Incident
In the case of a 3-phase system incident, supervision must be blocked. The device detects a 3-phase incident
with a jump in the current. This change is detected via the internal signal Jump I or when the change in
current of a phase current exceeds the threshold value 3ph.fail. - phs.curr. jump. The change in
9.3.2.4
Supervision Functions
9.3 Supervision of the Secondary System
SIPROTEC 5, Overcurrent Protection, Manual 1247
C53000-G5040-C017-8, Edition 07.2017
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