ETAP Short circuit study results using Current limiting fuses to reduce SCCR duty.

[power2engineer]

Does anybody have noticed the use of Current limiting Fuse (CLF) does not change available short circuit current results on the load side of the fuse performing ETAP short circuit study but then what is the explanation for the CLF does reduce the Peak let through current and short circuit duty on the downstream equipment ?

 

[Kiribanda]

CLF fuse will not offer CL action for all currents. During the SC study you will get the SC (sym) current passing through the fuse.
All current limiting fuses have CL curves. Then, you should check whether that SC (sym) current is above the minimum current
limiting value shown in CL curve, depending on the fuse rating.
If it is not above that value then the CL fuse will not go into CL action of operation. Then normal melting time is applicable.

 

[dpc]

It isn't that simple. The program is going to calculated the short circuit current as if the fuse is not there. If you want to take into account the impact of an upstream CLF in relation to the SC rating of a downstream breaker, you will have to get that information from the breaker manufacturer. This is determined by test. As noted, current limiting fuses are not always "current-limiting".