The system here in New Zealand is a M.E.N system or Multiple Earth Neutral, standard low voltage is 230v/400v, polyphase,.

Our transmission is in the form of 220 or 110 KV for transmission, stepped to 33KV for distribution then 11KV at supply subs, 400v to roadside.

All installations have a driven earth rod or bare copper where required. And a return to the supply transformer called a "Neutral cable" , the center point of the "Star" ( I think some call these "Wye") transformer is also referenced to earth.

When wiring an installation we don’t use a ringmain i think they have in the UK, Instead a radial feed from the distribution board. With say 5-6 outlets (doubles) normally this would be run in 2.5mm2 TPS but 1.5mm2 would be suitable if cable run is kept short, fused by a 20 Amp MCB. RCD protection is not mandatory (YET) unless run out doors or in a require zone these must operate at, (Let me get this right) 30mA within 300 ms for personal protection.
Minimum earthing conductor size is 4mm2 and 16mm2 for works.
There is lot else no doubt, if you are interested let me know,
nice to see you all again
Craig :-)