Upstream breaker Vs Downstream breaker

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Charz

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When two breakers are in series, in any situation does the upstream ground fault relay operates faster than downstream phase over current relay? should the downstream phase over current relay to be coordinated with upstream ground fault relay?

First off, does a ground fault relay operates for a phase fault?
 
If the two devices are not selectively coordinated, it is very possible that the upstream device will open first.

I have seen this happen with a ballast fault on a 20 amp, 277 volt branch circuit taking out the building main that had GFP protection as required by 230.95. Typically this has happened because no one ran the numbers and made the correct ground fault trip settings on the GFP main. They come from the factory set at their lowest possible settings.
 
Charz said:
When two breakers are in series, in any situation does the upstream ground fault relay operates faster than downstream phase over current relay? should the downstream phase over current relay to be coordinated with upstream ground fault relay?

First off, does a ground fault relay operates for a phase fault?
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I guess it works the same way! If either breaker trips, the downstream load loses power! Unless there are other loads that are being supplied by the upstream breaker, you need to coordinate it with the downstream breaker.
 
don_resqcapt19 said:
If the two devices are not selectively coordinated, it is very possible that the upstream device will open first.

I have seen this happen with a ballast fault on a 20 amp, 277 volt branch circuit taking out the building main that had GFP protection as required by 230.95. Typically this has happened because no one ran the numbers and made the correct ground fault trip settings on the GFP main. They come from the factory set at their lowest possible settings.
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I've seen this happen many times. Once someone ground faulted a 277 volt toggle switch and tripped the GFPE protection on a 1600 amp busduct riser knocking out 1/2 the buildings lights, another time the GFPE was set to its lowest level and tripped while I was in an elevator where I got stuck for 20 minutes in the dark (new building and EM generator was not installed yet).
 
infinity said:
I've seen this happen many times. Once someone ground faulted a 277 volt toggle switch and tripped the GFPE protection on a 1600 amp busduct riser knocking out 1/2 the buildings lights, another time the GFPE was set to its lowest level and tripped while I was in an elevator where I got stuck for 20 minutes in the dark (new building and EM generator was not installed yet).
Click to expand...
Ours was a mistake of an electrician trying to reverse the rotation of a big motor (460V, 600A bkr), he took one conductor from phase A nd swapped with one conductor on the B phase! The problem was, the motor lines were made up of two conductors per phase! The actions of the electrician resulted to a bolted fault at the bucket terminals The 3200A main breaker tripped ahead of the 600A breaker! The substation went dark!
 
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