Logic
[loproire-181111-01.tif, 2, en_US]
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
Summary of Contents for 6MD85
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