Ground fault coordination with downstream fuse 1

[CanEnergy]

When coordinating a feeder fuse in a switchgear line up with upstream main or substation breaker, would you coordinate the fuse with phase or ground element of the breaker?Thanks

 

[davidbeach]

Yes.

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982

 

[che12345]

I have the following opinion for your consideration.
1. This is the coordination between upstream CB and downstream Fuse. It is Yes as advised by Mr. David.
2. It is always desirable that the Fuse to blow , with the CB remain close, up to the short-circuit current kA level. However, is may be fully/partially; when the fuse current rating is close to the CB current rating.
3. a) Upstream ACB with LSI, where I current and time delay are adjustable. Adjust I with a small time delay would ensure clear the Fuse characteristic curve.
b) Upstream MCCB with LSI, with I adjustable but with NO time delay. In this case, coordination may be Partial, i.e. up to certain level; but not up to the full short-circuit kA level.
Che Kuan Yau (Singapore)

 

[CanEnergy]

"Yes"in a sense that fuse should coordinate with Ground OR phase element? Which one or both.

 

[cranky108]

Both.

 

[CanEnergy]

Does transformer connection matter?
Primary Delta or Wye?
If a fault within a delta transformer happens , it will evolve to phase fault quickly so coordinating with ground element results in small fuse rating that causes miscoordination with LV breaker settings curves

 

[davidbeach]

You want the fuse to trip first for any fault. The phase overcurrent elements are active for all faults, the ground for any that involves ground. For some faults, for some current ranges, you're coordinating with the phase curve and for others you're coordinating with the ground curve.

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982