Siemens Sentron 3VA Manual page 343

Advantage of ZSI:
Regardless of the number of series-connected molded case circuit breakers, all short circuits
in the network greater than I
circuit clearance times should be minimized, particularly in the case of system short circuits
of very large magnitude.
Note
Backward compatibility
The ZSI function is compatible with the ZSI function of the 3VL and 3WL molded case circuit
breakers.
Connection
Use of the ZSI function is conditional upon the connection of a dedicated EFB300 external
function box to each 3VA6 molded case circuit breaker. The EFB300 allows molded case
circuit breakers to communicate with one another, a capability which is a basic requirement
for the ZSI function.
To permit utilization of the ZSI function, EFB300 external function boxes must be
interconnected as illustrated below:
3VA molded case circuit breakers with UL and IEC certification
Manual, 01/2019, L1V30435333-01
but less than I will have a delay of no more than 50 ms. Short-
st i
Accessories
4.9 EFB300 external function box
341