Logic
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Figure 5-95 Logic Diagram of the Current-Flow Criterion Function Block (1/3-Pole Circuit Breaker)
The phase currents are provided via the interface to the protection function group.
The I open signal of one phase is generated if one of the following conditions is met:
•
A phase current falls below the set threshold of the Current thresh. CB open parameter. The
hysteresis stabilizes the signal.
•
The corresponding phase current, for example, I A, falls below 10 % of the phase current when the trip
command arrives. If the current does not drop until after a delay due to current transformer influences,
an open pole can therefore be detected quickly even after a high-current fault on the line.
With the Current thresh. CB open parameter, you define the minimum current as the criterion for a
deactivated line. The parameter lies in the Circuit-breaker function group. It acts both in the Circuit-breaker
function group, for example circuit-breaker position recognition, and also for the process monitor in the
protection function group.
If a protection function group with integrated process monitor is connected to several FG circuit-breakers, the
Current thresh. CB open parameter is present in each FG circuit-breaker. The smallest setting value of
the parameter Current thresh. CB open is used.
Application and Setting Notes (Current-Flow Criterion)
Parameter: Current thresh. CB open
•
Recommended setting value (_:2311:112) Current thresh. CB open = 0.100 A
The Current thresh. CB open parameter is used to define the threshold for the leakage current as the
criterion for a deactivated line.
Set the Current thresh. CB open parameter so that the current measured when the feeder is deacti-
vated falls below the value of the Current thresh. CB open parameter with certainty. The hysteresis is
additionally active if the threshold is exceeded.
If parasitic currents, for example, due to induction, are ruled out when the feeder is deactivated, set the
Current thresh. CB open parameter sensitively.
Siemens recommends a setting value of 0.100 A.
5.8.4
Function-Group Types
5.8 Process Monitor
294 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017
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