In metal clad switch gear DC grounds are a nightmare. An unintentional ground from a swingdoor may appear and disappear depending on the moon. Battery grounds are never a problem when you have them but when you have two at the same time anything can happen. They are the cause of 70% of the...
This image is how i had it explained to me that helped me understand this. Remember that the generator is trying to maintain the same potential difference between poles. So if one pole is shorted during a ground fault you get the effect of sliding all three over.
Clay
Pardon my quick sketch...
