GFP Nuisance Tripping

Status
Not open for further replies.

2450

Member
Ground Fault Protection Nuisance Tripping:
I am trying to determine the cause of the nuisance tripping on a GE 2000A/3P, 4-wire fusible switch feeder with an integral GFP. This feeder feeds a 2000A, 480/277V, 3ph, 4w distribution board that supplies power to (4) chillers and a bunch of pumps and misc. motor loads. Chillers 1,2,&3 are each rated at 261FLA, and chiller 4 is at 290FLA. The net total connected load on the distribution board is about 1600A. The GFP is currently set at the max. setting (1100A trip, max. time delay). When all 3-chillers, pumps and assoc. motor loads are on line, the GFP works OK. But the moment chiller #4 is put on line, the GFP trips instantly, shutting down the whole feeder distribution. The electrician tried to isolate or disable the GFP by removing the fuse block that feeds the GFP control circuit. Again, the GFP trips when the fourth chiller was put on line. I suspect that the GFP is defective, or there is improper connections (polarity). It seems that the GFP is reading the feeder 3-phase load current as imbalance and interpreting the error signal a a fault situation. Any ideas or recommendations on how to fix this problem? Thanks very much!
 

bob

Senior Member
Location
Alabama
Re: GFP Nuisance Tripping

I would try putting the #4 unit on line without the other load and see if it trips.
 

2450

Member
Re: GFP Nuisance Tripping

Originally posted by bob:
I would try putting the #4 unit on line without the other load and see if it trips.
Bob,we tried all combinations of three chillers ( 1-2-3;1-2-4;2-3-4;3-1-4)and the GFP worked OK. But as soon as all four chillers are put on line, the GFP trips.
 

2450

Member
Re: GFP Nuisance Tripping

Originally posted by dereckbc:
Is there a generator involved?
Yes, actually this 2000A feeder w/ GFP feeds a 2000A,4-pole automatic transfer switch powered (emergency) from a 1600KW standby generator.
 

2450

Member
Re: GFP Nuisance Tripping

Originally posted by hurk27:
Sounds like the #4 compressor has a ground fault in it's winding or in the wiring
OK, if the #4 compressor is faulted, then why is it that when we run Chiller #4 with any combination of the other two chillers the GFP did not trip. Only when all four chillers are put on line when the GFP trips. Thanks again for your reply!
 

hurk27

Senior Member
Re: GFP Nuisance Tripping

I think I see where the problem is.
The first three chillers draw about 783 amps. and you have said you have a connected load of 1600 amps. If your load total is over 1400 amps then the startup (lockrotor) current of the #4 chiller could push your service over the 2000 amp rating.
 

bob

Senior Member
Location
Alabama
Re: GFP Nuisance Tripping

It seems that the GFP is reading the feeder 3-phase load current as imbalance and interpreting the error signal a a fault situation. Any ideas or recommendations on how to fix this problem? Thanks very much!
If units 1,2&3 or running you have a load of 261x3= 783 amps. If what you say is true then the starting of unit would draw about 1450 amps causing the unit to trip. Can you put a clip on amp meter an set it to read the peak amps at the relay with only 3 units running? You should not read anything on the GFP. Anything over 1100 will trip the unit.

[ July 30, 2004, 11:12 PM: Message edited by: bob ]
 

hurk27

Senior Member
Re: GFP Nuisance Tripping

This is what I'm thinking as he did say he removed the fuses to the GFP control circuit which would only leave the OCPD part of it in operation.
Maybe I'm wrong but it seems like the start up current is pushing it over the limit.
 

charlie tuna

Senior Member
Location
Florida
Re: GFP Nuisance Tripping

most g.e. switchboards do not use fuses on the ground fault system. first make sure the white pilot light is "on" near the ground fault reset button. if you remove the fuses and this light stays "on" --those ain't the fuses to the ground fault system. usually, the ground fault network is fed by a three pole twenty or thirty amp breaker located above the main switch. as long as that pilot light is "on" the system is covered on ground fault...note:make sure the lamp is good!
 
Status
Not open for further replies.
Top