GROUND FAULT RELAY (REQUIREMENTS)

[PE (always learning)]

Hey everyone,

I have a question pertaining to where ground fault relays are required within a system. I understand that ground fault relays are required for 480V service disconnects 1000 amps or more, but does this only apply to service disconnects? I have a system where we have 480V 2000 amp main distribution panel with a 2000 amp main circuit breaker that does have a ground fault relay, but there is a 1000 amp branch breaker on this panel that does not have a ground fault relay. Does this 1000 amp breaker require a ground fault relay? Picture of the one line is attached.

Best Regards

 

[texie]

Hey everyone,

I have a question pertaining to where ground fault relays are required within a system. I understand that ground fault relays are required for 480V service disconnects 1000 amps or more, but does this only apply to service disconnects? I have a system where we have 480V 2000 amp main distribution panel with a 2000 amp main circuit breaker that does have a ground fault relay, but there is a 1000 amp branch breaker on this panel that does not have a ground fault relay. Does this 1000 amp breaker require a ground fault relay? Picture of the one line is attached.

Best Regards

No in most cases. But if this a situation such as an emergency system where coordination is required then yes.

 

[PE (always learning)]

No in most cases. But if this a situation such as an emergency system where coordination is required then yes.

This is just a house panel for an apartment complex. So then the ground fault relay really only applies to service disconnects 480V 1000 amps or greater, unless we are dealing with a hospital? (or healthcare in general)

 

[texie]

This is just a house panel for an apartment complex. So then the ground fault relay really only applies to service disconnects 480V 1000 amps or greater, unless we are dealing with a hospital? (or healthcare in general)

Yes but you need to realize the ramifications and decide if this would be prudent practice. Consider that that in the case of a ground fault somewhere down stream in the system could put the entire place in the dark. While expensive to do, many would put GFPE at least on all the feeders so it could be coordinated with the main.
Edit to add: required coordination applies to more that just healthcare. Any Article 700 system for example.

 

[PE (always learning)]

I'm performing a power systems study for the project in question. We are a third party and were not involved in the design. The project has already been built and I am going through the system, and providing recommendations to the owner. The reason I'm asking is because I want to make sure whether we absolutely require a ground fault relay or not at this location. It would be preferred to not have to tell the owner that the engineer messed up and forgot to provide a ground fault relay where the NEC required it, but that is why I wanted to double check on here.

Also, I agree with you that providing ground fault relay at this location probably would have been a wise thing to do, but again if it's not required then I'm not going to push it.

 

[jim dungar]

Actually the NEC requires GFP on all devices 1000A and greater. For services see 230.95 and 215.10 for feeders (many, if not most, people interpret Exception No. 2 to not require GFP on feeders if it has been provided on the main device).

Personally, I like multiple levels of ground fault protection with the lower levels set to just coordinate with 30A branch devices. Statistically ground faults are more likely to occur than any other type of fault, so why not protect against them.

 

[PE (always learning)]

Actually the NEC requires GFP on all devices 1000A and greater. For services see 230.95 and 215.10 for feeders (many, if not most, people interpret Exception No. 2 to not require GFP on feeders if it has been provided on the main device).

Personally, I like multiple levels of ground fault protection with the lower levels set to just coordinate with 30A branch devices. Statistically ground faults are more likely to occur than any other type of fault, so why not protect against them.

In this scenario, the ground fault protection has already been provided on the upstream device (2000 amp main breaker), which means the 1000 amp branch breaker would qualify for the exception that "ground fault protection is not required on feeders where there is up-stream ground fault protection."

Again, this is not my design, I'm a third party doing the power systems study for a project that is already built, but I do agree with you that if I were designing this I would try to add layers to my ground fault protection. I just don't want to point out a major cost issue if it's not absolutely required.