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Why do circuits 32 amps and under require a 0.4 second disconnection time at 230 volts, but circuits over 32 amps are legally allowed 5 seconds? 115 volts for 5 seconds is enough to cause injury to the body.

Can anyone tell me if the neutral is distributed aboard ships and if it is earthed?

Ok, say you had a building that needed backup power. Do any British Regs require that the loads be subdivided onto different branches and different automatic transfer switches based on type and priority?  

Why is earthing of the neutral forbidden at the supply transformers in a 3 phase 3 wire system? This has me beyond words confused. 

Is there any real danger in using a 0.8 seconds as disconnection time for 150 volts line to ground? Or would a sweet spot at 0.7 seconds work? Call me cheap but I don't want to use 0.4 seconds unless I really have to.  

Anyone have a list of resistance values per foot or meter for 1.5, 2.5 4mm2 ect for twin and earth, cable in conduit and swa cable?  Also how to obtain Ze when the supply transformer is customer owned, impedance known and assumed to be fed by an infinite MV source.