generator ground fault

[jdorsey]

when there is a breaker @ the generator and (3 Phase) you are not breaking the neutral @ the transfer switch and a fault occurs phase to ground in the transfer switch while the generator is running(as a back up loss of utility power) and you did not bond your equipment ground and neutral because the neutral was not broke what path does the fault follow and which breaker should trip? I hope this made sense ( a fault normally follows the path back to the source

 

[don_resqcapt19]

The path is the same as when you are on utility power. The fault travels back to the main bonding jumper and then on the neutral to the generator.

 

[Pierre C Belarge]

The path is the same as when you are on utility power. The fault travels back to the main bonding jumper and then on the neutral to the generator.

This is one of the reasons why it is so important to install the required signs at the proper locations as per NEC.

 

[tom baker]

Exactly, Pierre.
There are signs required for generators (actually emergency systems, standby systems) that are seldom posted:
See section 700.8, 701.9 and 702.8
Plus the signs required in Art 225 on multiple sources of supply.

 

[stevee]

The path is the same as when you are on utility power. The fault travels back to the main bonding jumper and then on the neutral to the generator.

I get what you are saying, I also understand the original question. Here's my look (I'm not disagreeing just adding to)

If the neutral is not opened in the transfer switch you don't install a MBJ in the generator therefore the theoretical path for a ground fault occuring in the transfer switch is as follows:

1. Ground Fault occurs in Transfer switch
2. Fault current follows grounding path to the main bonding jumper in the main service panel
3. Fault current flows thru the main bonding jumper located in main enclosure
4. Fault current flows on neutral conductor back to transfer switch
5. Fault current returns to generator on the neutral

So, the current still returns to it's source, it just takes a round-a-bout path.

 

[mdshunk]

Anybody have any pictures from the field of the required signage that has been used for optional standby system?