Andy1845c said:
You have 440vac in homes in New Zealand? I know line voltage in 240v in many parts of the world, but didn't relize you could get 440v
440V is three phase, three separate 240V lives, 120 degrees apart, it may, or may not, have a neutral connection.
Essentially it's all three phase in the UK (and related countries), the substation provides a four core output, neutral and the three lives. As it goes down the street the first house will get a connection to neutral and L1, the second house neutral and L2, and the third house neutral and L3, and so on. This means the load is spread fairly evenly over the three different phases, resulting in little current in the neutral conductor - this means you can save money by having a thinner cable for the neutral.
If you have industrial premises, you can have a three phase supply, which is required for large motors and equipment - we have a small goods lift at work, and that uses a small three phase motor. Also different parts of the buildings are on different phases, so you can lose power in one part, and not the others.
Because of the presence of 440V between phases, there are strict regulations of how far mains sockets on different phases have to apart, and also the length of leads allowed on portable appliances. I've no idea what the actual figures are?, but you can imagine if the sockets are 20 feet apart, and the leads only 6 feet long, there's no way you can have one of each in either hand.
However, it's rare to have three phase in domestic premises, although if you have a workshop you may need it for the machines, and you could request it.