We have a power system that is 240 volts single phase or 415 volts 3 phase.
The mains in the street have 4 wires, 3 x 240 volts (active) and a neutral. Between each of the 240 volt wires is 415 volts and between the 240 volt active and the neutral is 240 volts.
Most modern homes are supplied with an 80 amp 2 cable system IE 240 volts.
If the current draw is greater than that and no 3 phase motors are installed then they can run 2 actives (phases) in and a neutral.
There are no transformers in these homes for the power supply, they just run some things off one active and some things off the other active.
If the load is too great for this 2 phase set up or you have one or more 3 phase motors then they will connect up 3 phases to your home (3 actives and a neutral) The power outlets are to be balanced over the 2 or 3 phases.
Power outlets in the homes are rated at 10 amps (2,400 watts) there are also available 15 amp outlets (3,600 watts) and 20 amp outlets (4,800 watts) although most homes do only have the 10 amp outlets. All outlets are earthed, and the current regulations require the earth and neutral to be joined in the fuse box.
The way the power outlets are configures is that a 10 plug will fit into a 10 amp, a 15 amp and 20 amp outlet, a 15 amp plug will fit into a 15 amp and a 20 outlet while 20 amp plug will only fit into a 20 outlet.
There are 30 amp outlets, but there are very rare and in general and equipment using a lot of power, is wired direct into an isolation switch and not an outlet.
Here on the 240 volt systems the active is red or brown, the neutral is black or blue and the earth is green and yellow (striped).
That is what we have for most homes, however in a few parts of the country where there are quite some distances between the homes and power supplies they do have an alternative system. it is 480 volts and only one cable, it is called SWER (Single Wire Earth Return) at the home on a pole they mount a transformer to supply 240 volts to that home.