Zone Selective Interlocking
5.2 Examples
3WL/3VL circuit breakers with communication capability - PROFIBUS
System Manual, 03/2011, A5E01051353-02
113
Short-circuit in grading level 2
●
Q1 and Q3 determine a short-circuit, Q4 does not. This is why Q3 also does not receive
any ZSI information from Q4, but in turn provides ZSI information for Q1. On the basis of
this information, Q3 knows that it is closest to the short-circuit and trips with a delay of t
ZSI
= 50 ms instead of t
sd
= 200 ms.
Time saving = 150 ms.
●
Although Q2 receives the ZSI-IN signal, it is not traversed by the overcurrent.
For this reason, no action is taken with Q2.
Short-circuit in grading level 1
Only Q1 determines this short-circuit. It also does not receive information from a subordinate
grading level, and therefore trips after t
ZSI
= 50 ms.
Time saving = 250 ms.
5.2.2.4
Cancelation of the ZSI OUT signal
●
ZSI OUT at short-circuit
after removal of the short-circuit current, but after 100 ms at the earliest
●
ZSI OUT at ground fault
after removal of the ground fault current, but after 500 ms at the earliest
●
MV OUT for medium voltage
after removal of the overcurrent, but after 500 ms at the earliest
●
The ZSI OUT signal is canceled at the latest after 3 s
