Ground Fault Protection Coordination

[PE (always learning)]

I understand the process of coordinating ground fault breakers. There is obviously a ground fault pickup and delay that needs to coordinate with upstream and downstream ground fault settings. The part that I'm confused with is once I get to my furthest downstream overcurrent protective device with ground fault trip settings, do I need to make consideration on whether that device coordinates with the phase protection downstream.

For instance, I'm working on a project where I have a 3000 amp main (480/277V) with my ground fault protection set with a GFPU of 1200A and a GFD of 0.5 seconds. My next level of ground fault has a 800 amp breaker with a GFPU of 320-800 amps and a GFD of 0.1-0.3 seconds.

I set my GFPU on the 800 amp breaker to 800 amps and my GFD to 0.3 seconds (highest settings that still coordinate with upstream overcurrent). This allowed for coordination with the upstream ground fault settings and also allowed for coordination with the single pole 20 amp breakers downstream in the panel. Is this the right idea? Coordinate with upstream ground fault settings and coordinate with the downstream 20 amp breaker phase settings.

 

[jim dungar]

I usually chose coordination with downstream 30A devices. I felt most 'live' work occurs on these smaller lighting and receptacle circuits

 

[PE (always learning)]

I usually chose coordination with downstream 30A devices. I felt most 'live' work occurs on these smaller lighting and receptacle circuits

Gotcha, that makes sense to me, I've got my ground fault settings for the 800 amp breaker at the highest possible setting right now which does coordinate with the downstream 30A and 20A devices, but I was just curious if I'm defeating the purpose of ground fault protection by setting it so high.