Siemens 7SJ85 - Application and Setting Notes (Current-Flow Criterion); Circuit-Breaker Condition for the Protected Object

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.
Circuit-Breaker Condition for the Protected Object
Logic
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Figure 5-92 Logic Diagram of the Circuit-Breaker Condition for the Protected-Object Function Block
The circuit-breaker position recognition in the Circuit-breaker (CB) function group provides the circuit-breaker
condition by way of the internal signal CB pos. recogn. prot. obj. .
If a protected object is supplied via 2 circuit breakers (CBs), for example with the 1 1/2 circuit-breaker layout,
then the circuit-breaker switch position of the protected object must be determined with the aid of both circuit
breakers. In this case, the Circuit-breaker position recognition for the protected object function block
connects the individual CB states. The connection provides the internal
CB pos. recogn. prot. obj.
signal to the other function blocks of the process monitor and to other functions, for example, Trip in the
event of weak infeed and Echo function for teleprotection method, within the same function group.
If one of the following 2 conditions is met, the
CB pos. recogn. prot. obj. signal is in the Open state:
•
All connected circuit breakers signal the Open state internally.
•
The >Disconnector open input is active.
5.8.4
5.8.5
Function-Group Types
5.8 Process Monitor
296 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017