277V GFCI Breaker, Anyone have any info?

[milwaukeesteve]

I have a circuit for outside lights that is 277Volts. There is no Ground Fault protection for this circuit. Unfortunately the only ground fault breaker is the Main for the building.
I have had a fault in this circuit, and it has brought down the building.
I would like to put some GFI protection on this branch circuit before the Main GFI trips.
Does anyone know of how I can do this or what can be done for this?
The Panel is Square D 200A MainLug 277/480 Panel.

 

[petersonra]

Re: 277V GFCI Breaker, Anyone have any info?

is there any guarantee the GFI on this branch circuit would trip before the main does?

 

[don_resqcapt19]

Re: 277V GFCI Breaker, Anyone have any info?

Are you sure the settings for the main breaker are correct. The ground fault trip may be set too low.
Don

 

[rcwilson]

Re: 277V GFCI Breaker, Anyone have any info?

I don't know of a Square D 277V breaker with integral GF, except in the larger 3-pole. Cutler Hammer has the GHBGFEP 277V breaker with GF. It takes two pole spaces in the panel.

You could get a stand alone GF relay (Cutler-Hammer Type GFR or GFM) and change out the circuit breaker to one with a shunt trip.

 

[milwaukeesteve]

Re: 277V GFCI Breaker, Anyone have any info?

The Main GFCI breaker does have settings on it.
I am not going to adjust the levels until I have a real solution to this problem.
If I do install some kind of downstream GF protection, theoretically I can adjust so the downstream will trip sooner than upstream.

I have thought about installing a 3pole GFCI breaker for the distribution breaker, that way ALL of the lighting is GF protected. If I trip out the lighting, then I will just be in the dark, but then the phones, computers, elevator... won't be without power.

Please, more suggestions welcome.

 

[james wuebker]

Re: 277V GFCI Breaker, Anyone have any info?

milwaukeesteve, did it trip the breaker on the lighting circuit? If it didn't then you might have a problem with that. Don is correct also that you might need to adjust your GFCI main breaker. Something like what you are telling us about the light shouldn't take down your main unless it's not set correct. Let me know what you come up with.
Jim

 

[pierre]

Re: 277V GFCI Breaker, Anyone have any info?

Like Don has said, the Main seems to need adjustment - not something you should be doing, but a rep from SqD. A 20 amp standard circuit should not trip a GFI protected Main of that size - no matter where it is located in the system.

 

[jim dungar]

Re: 277V GFCI Breaker, Anyone have any info?

Most main GFPs come from the factory set to the minimum current (usually 200A) and the minimum time (often 1 sec). A 20A branch breaker usually has a magnetic trip range of about 10x for 6 sec to allow for motor starting.

If this is your situation the main GF will trip before the branch can clear a fault.

You need someone to perform a coordination study, not add another level of GFP. Ask for the main GF to be coordinated with the largest feeder/branch breaker. Personally, I usually stop at a 400A max device.

 

[milwaukeesteve]

Re: 277V GFCI Breaker, Anyone have any info?

If there is a fault to ground in the circuit, the 20Amp branch OCP will not trip it. It would either be the first breaker that the fault sees, which is the main via the transformer, or the at the Ground Fault Protection. Both of which are the main breaker.
I would like to some how put in that 'extra' Ground fault protection so I don't have to rely on settings, pickups, and coordinations.
I just don't know how to physically do it with the equipment and voltages I have present.

 

[jim dungar]

Re: 277V GFCI Breaker, Anyone have any info?

The easiest method would be to replace your existing breaker with one that has a shunt trip mechanism. Then mount your separate ground fault sensing relay and wire it so that it will operate the shunt trip. This is basically what is done with main fusible switches.

There are several vendors of stand-alone ground fault devices like Square D, NK Technologies, and Bender. Or maybe you could use the High Power unit from Leviton, I know the contacts are rated 120V but I'm not sure about the sensor.

In any case, you will still need to co-ordinate the settings of your new GF with the existing main GFP.