During my years of studying electrical circuits and transformers, I learned about how in a 240/120 volt feeder to a home, if you get an open neutral wire on your mains, you can get 240 volts across your 120 volt loads, potentially damaging connected loads rated at 120 volts. Well, I have now seen it and confirmed that it can happen. I had a situation on a pump house feeder that had on open neutral and the phase voltage was 215 to neutral. In this case there was no 120 volt circuit really, it was a 3 phase pump, but the mains hot conductors all read 215 volts to ground (on a 3 phase 208/120 service.) The grounded neutral also serves as the grounding conductor for the system, so it was dangerous if a fault occurred with no return for the fault current to open the fuses. The faulted neutral was underneath a condo foundation installed years earlier. I had to by pass it and restore the line.
The life & times of my electrical world!