Description
2.5 Protection functions
3VA molded case circuit breakers with UL and IEC certification
Manual, 01/2019, L1V30435333-01
77
Operating principle
The diagram below demonstrates the operating principle of zone-selective interlocking:
- - - Communication cable
t
i
"Virtual" tripping time of I protection
A
Output, transmits the blocking signal
t
SD
Delay time setting of S protection
E
Input, receives the blocking signal
t
ZSI
Delay time of all molded case circuit breakers
which detect the short circuit but do not receive
a blocking signal when ZSI is activated
The ZSI function acts on the S and G ranges of the tripping characteristic. Currents within
the I range (instantaneous short circuit) continue to cause instantaneous tripping.
