Genset grounding, ELR question

[Falang]

I'm trying to understand the function of the earth-leakage-relay on a 400V genset.

The ELR on my genset is a toroid type, with 3 phases and neutral travelling through the toroid. My understanding is it uses the principal of 0 net sum current between 4 conductors to sense an imbalance (fault), and can then in turn trip the genset main breaker. For this to happen, some current would have to be travelling beyond the confines of the conductors travelling through the toroid.

I think i understand this, but the part that is confusing me is that my genset came from the manufacturer with a floating neutral, it is not bonded to the frame of the genset. So, doesn't this mean that, as a stand-alone piece of equipment, the genset can never trip the ELR, even in a line to frame situation? And doesn't this also mean that, even if the system the genset is connected to is neutral-ground bonded in a panel, that all fault currents would still have to return to the genset through the neutral wire, and thus making the ELR pointless?

I feel there's a gap in my knowledge of the ELR function somewhere. Can anyone shed some light on this?

 

[Smart $]

Not an expert on the subject, but FWIW I agree with your assessment.

 

[brian john]

1. Is the generator the primary source or will this interface with a utility service through a 4 pole Automatic Transfer? If you have a 3 pole ATS you would not bond the XX)/Neutral and the ERL will not function as presently designed.
2. In either case you are correct you need the X0/Neutral to be grounded in the generator for the ERL to function properly?
3. It may be the that the manufacture over looked this connection, or the folks that are responsible for the connection did not know there was an ERL circuit breaker being installed.
4. I would contact the manufacture to get some input to this but as you noted for the ERL to function you will need to bond the X0/Neutral