> The neutral is also somewhat regularly grounded in the building's I've seen and atleast one grounding point is required at the distro point.
Hmm. Are phase-to-neutral loads permitted? If so, does this mean that the building and ground are allowed to carry neutral currents? This seems like a bad idea.
I’m not an electrician, but I’ve seen enough problems caused by “objectionable current” (the US code name for currents through what is supposed to be ground even in the absence of a fault) that I think that neutral should be treated as a hot wire whose voltage to ground just happens to be quite low. This would involve all breakers switching the neutral as well as having a reliable mechanism to detect neutral-to-ground faults.
Newer US GFCI devices are supposed to detect neutral-to-ground faults, so that’s a start, but I don’t think any of them will actually disconnect the neutral if such a fault is detected. They do this by inductively coupling a low voltage 120 Hz common mode waveform on hot + neutral, or maybe just on neutral. It’s a cute trick.
