Ground Fault Protection on feeders vs Mains

[mull982]

I know NEC requires ground fault on any service 1000A or above. In lieu of having the ground fault protection on the mains can you have the ground fault protection on the feeder breakers?

Does the Main at a 480V LV substation located downstream of the MV distribution system in a plant still need to have ground fault per the NEC or does that requirement only apply to service entrances?

 

[jumper]

Are you asking if feeders require GFPE for equipment =/>1000A like services?

If so, then yes.

215.10 Ground-Fault Protection of Equipment.
Each feeder disconnect rated 1000 amperes or more and installed
on solidly grounded wye electrical systems of more than
150 volts to ground, but not exceeding 600 volts phase-to-
phase, shall be provided with ground-fault protection of
equipment in accordance with the provisions of 230.95.

 

[GoldDigger]

I think he is asking whether the GFP on the main can be omitted if there is GFP on all of the feeders. (No direct branch circuits).
I would say no, but if there is no main, then GFP on all of the service disconnects should be OK.

Sent from my XT1585 using Tapatalk

 

[mull982]

I'm looking at a situation with a M-T-M LV substation in a plant fed from 4.16kV-480 transformers in the plants MV distribution system. To my knowledge this is not a "service" so the service requirements would not apply.

The 2000A Main and tie breakers at the LV Switchgear do not have ground fault protection but the feeder breakers do. I'm trying to determine if the Mains are required to have ground fault protection or if the fact that all the feeders have ground fault meet the code requirements.

It sounds like any feeder breaker located anywhere in the system must have ground fault protection if it is rated 1000A or more?

 

[ATSman]

I'm looking at a situation with a M-T-M LV substation in a plant fed from 4.16kV-480 transformers in the plants MV distribution system. To my knowledge this is not a "service" so the service requirements would not apply.

The 2000A Main and tie breakers at the LV Switchgear do not have ground fault protection but the feeder breakers do. I'm trying to determine if the Mains are required to have ground fault protection or if the fact that all the feeders have ground fault meet the code requirements.

It sounds like any feeder breaker located anywhere in the system must have ground fault protection if it is rated 1000A or more?

If you own the two xfmrs in the LV double-ended sub then I believe you are correct, this is not Service Entrance equipment and not subject to the code section referenced by Jumper. I think the confusion comes from how the code is worded when they say "feeder" and mean "main disconnect" of service entrance equipment and don't mention "Service Entrance." Almost all (there are exceptions) of the commercial installations we see (high-rise bldgs, stores, restaurants, etc.) with main breakers/ disconnects rated 480V, 1000A or greater only have GFP on the main disconnect since it is code required. The option to protect the feeders is not taken do to economics: they don't want to spend the extra money. In a heavy industrial environment (Telco, data centers, hospitals, mfg plants, pump stations, etc) it is a different world. GF coordination to quickly isolate the faulted equipment is critical. It all comes down to risk and the cost of unplanned downtime $$$$$$$$$ :jawdrop:

 

[jtinge]

If you own the two xfmrs in the LV double-ended sub then I believe you are correct, this is not Service Entrance equipment and not subject to the code section referenced by Jumper. I think the confusion comes from how the code is worded when they say "feeder" and mean "main disconnect" of service entrance equipment and don't mention "Service Entrance." Almost all (there are exceptions) of the commercial installations we see (high-rise bldgs, stores, restaurants, etc.) with main breakers/ disconnects rated 480V, 1000A or greater only have GFP on the main disconnect since it is code required. The option to protect the feeders is not taken do to economics: they don't want to spend the extra money. In a heavy industrial environment (Telco, data centers, hospitals, mfg plants, pump stations, etc) it is a different world. GF coordination to quickly isolate the faulted equipment is critical. It all comes down to risk and the cost of unplanned downtime $$$$$$$$$ :jawdrop:

I would be careful not to equate main disconnect with service entrance equipment. Not all buildings will have service entrance equipment, especially buildings on a campus distribution system not owned by the utility. In this case the supply to the builds will not be services but will be feeders. Thus the cite by jumper would be correct. I have crossed referenced the requirements for buildings supplied by feeders to those supplied by services if anyone is interested. In a majority of cases the requirements are identical or almost identical except for the distinction between feeder and service.

 

[ATSman]

I would be careful not to equate main disconnect with service entrance equipment. Not all buildings will have service entrance equipment, especially buildings on a campus distribution system not owned by the utility. In this case the supply to the builds will not be services but will be feeders. Thus the cite by jumper would be correct. I have crossed referenced the requirements for buildings supplied by feeders to those supplied by services if anyone is interested. In a majority of cases the requirements are identical or almost identical except for the distinction between feeder and service.

Ok if I understand you correctly then by code he is required to have GFP on the 2 mains even though they are not service entrance equipment, regardless if the downstream feeders have GFP?
Pls confirm.
Aside from this issue I thing the rest of my post has some merit as we see these installations on a regular basis. As a result, on older builds with 277V lighting, the shorting out of a 20A lighting ballast can travel back and trip a 4000A main breakers on a GF trip.

 

[kwired]

What Smart quoted was in 215 - which applies to feeders.

If you have GFP on the service wouldn't any feeders supplied by that service also be protected?

Where 215.10 would probably be most likely to require actually using a GFP on other then service disconnecting means would be for separately derived systems like the mentioned medium voltage distribution on a campus and 480/277 SDS to a campus building.

 

[jtinge]

What Smart quoted was in 215 - which applies to feeders.

If you have GFP on the service wouldn't any feeders supplied by that service also be protected?

Where 215.10 would probably be most likely to require actually using a GFP on other then service disconnecting means would be for separately derived systems like the mentioned medium voltage distribution on a campus and 480/277 SDS to a campus building.

What I was trying to point out was that there is a distinction between a service and the supply to a building by a feeder. A building supplied by a feeder could have the same requirements as a building having service entrance equipment. One is just supplied by a feeder and one is supplied by a utility.

I have attached a file that shows how the history of service has changed in the code over the years. I have another file that compare the code requirements between services and buildings supplied by feeders; however, it is too big to attach through a forum post.

I can send directly if requested through a PM.

 

[kwired]

What I was trying to point out was that there is a distinction between a service and the supply to a building by a feeder. A building supplied by a feeder could have the same requirements as a building having service entrance equipment. One is just supplied by a feeder and one is supplied by a utility.

I have attached a file that shows how the history of service has changed in the code over the years. I have another file that compare the code requirements between services and buildings supplied by feeders; however, it is too big to attach through a forum post.

I can send directly if requested through a PM.

All I was saying is if you have GFP on the service then the service GFP is already covering any sub feeders. Only separately derived systems would possibly be required to have other GFP.

 

[ATSman]

What I was trying to point out was that there is a distinction between a service and the supply to a building by a feeder. A building supplied by a feeder could have the same requirements as a building having service entrance equipment. One is just supplied by a feeder and one is supplied by a utility.

I have attached a file that shows how the history of service has changed in the code over the years. I have another file that compare the code requirements between services and buildings supplied by feeders; however, it is too big to attach through a forum post.

I can send directly if requested through a PM.

Thanks for the document.
Can you upload the other file to a cloud service such as Drop Box and provide us with the link?

 

[jtinge]

Thanks for the document.
Can you upload the other file to a cloud service such as Drop Box and provide us with the link?

Unfortunately I don't do cloud services or social networks so I don't know how to do what you are suggesting. If you have that capability and are willing to post the link, I am willing to email the document to you. Just PM your email to me.