That reminds me of a conference room at a Holiday inn, they said that some of the clients had plugged there laptops in and the chargers were smoking, turned out to be a failed neutral, that 2 phased the socket outlets.
As for 3 phase neutral currents, I recall they can be higher than the phase current, but i dont recall how.
We fit 3 phase gantries that have 3 outlets per phase, the 9 outlets allow a maximum 32a per phase, these gantries plug in with a 6mm 4 core to a 32 amp socket.
We had a run of the Neutral pin burning up, so i looked into the matter to no avail, due to the many combinations of being unbalanced, i think a clamp meter would have been easier.
something to do with working out the Vectors Victor