Earthing neutral

I suspect you are quite right - the IEC docs will be based on 230/400  practice; 690v 3 phase is much rarer, being really confined to larger factories, as mines and off shore do their  own thing and the only time you see 110v is on a UK building site where it is centre tap earthed so really 55-0-55, and the rest of  the continentals look at us funny when we do that. (and having worked in Germany I can say they do that on some other occasions too.?)


I suspect the thinking is the all final user 3 phase supplies that are wired as star could potentially at some point be made 4 wires from 3, and need treating accordingly the same. (I have seen factory kit with only the 3 phases supplied, no neutral so a 230V stolen between 1 phase and earth for example, it is not really permitted, but if it happens you do not want it to make the system dangerous.)

I suspect you are quite right - the IEC docs will be based on 230/400  practice; 690v 3 phase is much rarer, being really confined to larger factories, as mines and off shore do their  own thing and the only time you see 110v is on a UK building site where it is centre tap earthed so really 55-0-55, and the rest of  the continentals look at us funny when we do that. (and having worked in Germany I can say they do that on some other occasions too.?)


I suspect the thinking is the all final user 3 phase supplies that are wired as star could potentially at some point be made 4 wires from 3, and need treating accordingly the same. (I have seen factory kit with only the 3 phases supplied, no neutral so a 230V stolen between 1 phase and earth for example, it is not really permitted, but if it happens you do not want it to make the system dangerous.)