ELF Current Limiting Fuses: 3 Barrels fuses Vs one fuse

[D!NNy]

I recently found these fuses in one of the projects i am working on:

3 Barrrels Vs one: I am seeing more disadvantages over advantages in using 3 Barrels Vs one; correct me if i am thinking wrong.

1. Practically the element in the fuses in the 3 barrels wont be same, if for a case one of the fuse in this combination is gone and rest of them are still working we would never know that one of the fuse is gone?

2. if one the fuse is gone and still the system is energized in the next fault condition protective device may miss coordinate?

Thanks in advance.

 

[jim dungar]

I recently found these fuses in one of the projects i am working on:

3 Barrrels Vs one: I am seeing more disadvantages over advantages in using 3 Barrels Vs one; correct me if i am thinking wrong.

1. Practically the element in the fuses in the 3 barrels wont be same, if for a case one of the fuse in this combination is gone and rest of them are still working we would never know that one of the fuse is gone?

2. if one the fuse is gone and still the system is energized in the next fault condition protective device may miss coordinate?

Thanks in advance.

Multi-barrel fuses have been the standard construction method for MV fuses above 600A, for just about forever.

 

[templdl]

Multi-barrel fuses have been the standard construction method for MV fuses above 600A, for just about forever.

Yes, they are used when a point is reached when a single fuse isn't large enough. Then do come assembled as a multibarrel fuse though. I am not aware of a multibarrel fuse assembly being used for the 600v class.

 

[D!NNy]

Multi-barrel fuses have been the standard construction method for MV fuses above 600A, for just about forever.

My point is what if one of them is gone: ideally nothing is same
1. there is no indication
2. miss coordination

 

[GoldDigger]

My point is what if one of them is gone: ideally nothing is same
1. there is no indication
2. miss coordination

True, but think for a moment about what, other than a mechanical failure, would cause just one of the barrels to open:

1. Overcurrent just above the fuse rating: After some long period of time, one barrel will open, and unless the load happens to immediately shut off, the remaining two barrels, which are already hot and close to opening, will each see a 50% increase in current and will also blow.
2. Short circuit: The short circuit current will very quickly blow one of the barrels, or perhaps even all three of them simultaneously, and unless the short circuit is immediately removed, the other two barrels will also go in a small fraction of a second.

So it is unlikely, though possible, that a fuse will ever end up in the condition you describe other than as a result of a defect in construction.