Lyle,
This is an interesting subject actually and I say thanks for the information that you submitted with your post.
I must say that I'm a little rusty when it comes to Generator Installations.
I'm making a wild assumption in asking if the Generator is a Star (Wye) connected type?.
What I can gather, Lyle, this sounds like a problem with current beng introduced by the Star-point of the Generator, back into the Installation Earthing system.
I could be wildly off the mark here, but I would never fail to drive a seperate Electrode for a Generator, regardless of size.