Dear ;
Certainly, we have the same mainly kind of protections ” Overload & Short Circuit ” when using the standard fuses, and as the fuses haven't any mechanism, the protection against these faults are 100% assured. Personally, and for general protection, I use the fuses for some applications but not all time.
I prefer to use the fuses in the following applications :
1 – Fuses type ” Cylindrical ” for all control circuits as the breaking capacity for this kind is too high ” 100-120 kA “, so, we can use them at any levels of LV network whatever the values of the maximum short circuit currents, and also for some small loads ” 3 phases ” when there no motors, because the protection of phase missing ( fuse blown due to fault between phase & neutral ) is not assured by the standard fuses. Noting that with another kind of fuses ” Fuse with Striker ” using with a special fuse holder ” equipped with auxiliary contacts ” we can assure the protection for this fault, but the cost will be high.
2 – Fuses type ” NH without Striker ” to protect the Capacitors.
In general applicationsI ” Mains & Outgoings ” protections, I don't prefer to use the fuses for the following reasons :
1 – As the Tripping curves can't be modified, we can't find the necessary rating for all places in the network, especially when the values of the minimum short circuit currents or the earth fault currents are small.
2 – We can't realize in all cases the ” Discrimination or Selectivity ” either for Overload or/and Short Circuits Faults.
3 – We can't realize in all cases the ” Cascading or Buck-up “.
4 – If some loads are ” Motors ” and we use the standard fuses ( without Striker ) to protect these outgoings, we should absolutely use one of the following solutions to assure the protection against phase missing ( one fuse blown ) :
A – The Electronic Equipment ” Phase Failer “.
B – Using the ” Fuses with Striker ” with the special ” Fuse Holders ” or ” Switch-Fuse Disconnectors ” ( depending on the ratings )
equipped with auxiliary contacts.
C – Using the ” Electronic Thermal Relays ” with contactors.
5 – As the Earth Fault Current in ” TT ” earting system is small, the fuses can't assure the protection against Earth Faults, so, we should use also an ” E.L.P. “.
6 – The fuses' ratings that we can find too easy are ” up to 630 A “, where only some specialized manufactures produce ” up to 1250 A “.
7 – When we use the fuses, we should have the necessary stock of all fuses used in the project ( types & ratings ), to be able to replace any blown one.