Zone Selective Interlocking
5.2 Examples
3WL/3VL circuit breakers with communication capability - PROFIBUS
112
System Manual, 03/2011, A5E01051353-02
5.2.2.3
Example of 3 grading levels without coupling switch
The graphic below shows the functional principle of the ZSI function using an example in the
power distribution system. Both SENTRON VL and SENTRON WL circuit breakers are used
in different grading levels.
=6,
PRG
XOH
=6,
PRG
XOH
=6,
PRG
XOH
=6,
PRG
XOH
WVG PV
WVG PV
WVG PV
46(17521:/
46(17521:/
46(17521:/
46(17521:/
Short-circuit in grading level 3
●
The switches Q4, Q3 and Q1 detect a short-circuit. Q4 informs Q3 and Q1 via the ZSI
signal so that these do not trip in t
ZSI
= 50 ms.
●
Since Q4 in turn does not receive information (ZSI IN) from a subordinate breaker, it is
responsible for switching off the short-circuit as quickly as possible (with delay time t
ZSI
=
50 ms). If this does not happen because, for example, the switch is incapacitated, Q3
operates as a backup and trips after the time-selective setting time of t
sd
= 200 ms.
●
Although Q2 receives the ZSI-IN signal, it is not traversed by the overcurrent.
For this reason, no action is taken with Q2.