Ground fault CB coordination

[jaishreeram]

We have ground fault and phase functions active in some of our CB. My question is do we need to cordinate ground fault functions with either downstream or upstream CB? If yes,do they need to be cordinated with phase functions or ground functions of other breakers? And what if other breakers don't have ground fault functioning?
Thanks

 

[ron]

Coordinate ground fault characteristics with other ground fault characteristics of up and down stream devices. No need to coordinate with other phase functions.

 

[brian john]

What type of GFP are you using? Relay or part of the CB's OCP? Is there Zone Selective option available?

 

[templdl]

Hopefully you have ground fault pickup and delay setting on the breakers in question.
Delay can allow the downstream device time to trip.
However, pickup is another issue. I one adjusts the downstream device at a lower setting it may be assumed that it would trip sooner or trip at a lower GF level.
However, if there were a GF how can it be assured that it would be at a low enough value to only trip the breaker with GF tah is closest to the fault.
If the GF were of high enough value that was within the pickup of all breakers in series then all would see the same fault and it would be pot luck which one would trip unless there was a delay option.
It must be pointed out that ground faults are not predictable.
Some breakers have the ability to communicate with one another where all breakers see the fault and the upstream breaker sees that the drowstream breaker also sees the fault and allows the down stream breaker to trip clearing the fault.
.