I have to correct your last point Doc. 240V rms is, in layman's terms, the 'average' of the AC sine wave. The 'peak' voltage of 240V rms is about 340 volts. (339 point something).
(To clarify, as well as rms value of the sine wave, there is also something called the 'average' value. I used the term 'average' in the above explanation so non electrical people have a better chance of comprehending these concepts.)
Even if you accidentally touch one phase of a 3 phase system, you're still 'only' going to get a 240 volt (rms) wake up call.
If if you're ever unlucky enough (or stoopid) to touch 2 different phases of a 415 volt 3 phase system, you're gonna cop a peak voltage of about 586 volts. I don't know where you got the value of 678 volts from.
Just to explain a little further to those who are still awake and still following this, Australian mains voltage is 240v rms @50hz.
This means the 'average' (sic) voltage is 240 volts, but the actual voltage is like a wave. In one 'cycle' of this wave it starts at zero volts, in 5 milliseconds (mS), it rises to +340volts (ish) 5mS later drops to zero volts again then rises to -340volts (ish) and back to zero. This whole cycle takes 20mS and happens 50 times every second, which is where the 50Hz comes from.
If you get a 240volt 'kickinthepants', you're actually copping 340volts one hundred times each second. The good news is, your also getting zero volts one hundred times every second. (Gives you a break)
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