The commonest UK one is TN-S, where separate protective and neutral conductors run all the way to the substation and are grounded there.
Every house in my road, and many in my village have their supply taken from 4 wires on poles outside the house. Every house is connected to the lowest wire, and every house is connected to one of the three other wires. Yes, that's neutral at the bottom and the other three are the three phases. I'm not exactly in the sticks; I'm 4 miles from a major city centre!
I do not intend to have the lead water supply pipe replaced - although I do run the water for 1 minute before drawing any for drinking
Out of curiosity, what is the grounding arrangement TN-C-S, or TT? (The latter in my mind standing for not
Terre-Terre but
Truly-Terrifying)?
For those not in the know geographically, overhead (low voltage*) supplies are pretty rare in the UK. Not unknown, as the above proves, but I'd guess that the proportion of the total premises that are delivered overhead to the customer is in the low single figures percent. (I just tried to find actual figures but failed.)
Correction, I found figures. These are just based on total length of low voltage supply lines above or below ground, and one would expect rural supplies (where one finds most overhead delivery) to be physically longer and so use more length of cable per premise served. It takes 10 metres of cable to get to my (urban) next door neighbour; if that was rural it would be possibly hundreds of metres. So, 14.6% of UK low voltage distribution cable is above ground (European average 42.4%) - which I think is consistent with my guess of single digit percent premises served.
Only if perfectly balanced will it [neutral] be at 0V (except during lightning strikes and gross distribution problems!). ISTR a couple of volts being not uncommon.
The worst place for floating (relative to local ground) neutrals are light industrial trading estates where the demand balancing across phases can be all over the place, especially when there's big-ish machinery. Heavy industry tends to get individual three phase supplies and some thought put into designing the loading of them. Light industry shares one supply between many premises and there is little or no planning goes into load balancing. Add a few load dumps, some crappy power factors and you've got an 'interesting' supply to deal with.
* In the electricity supply world the term
low voltage gets used for everything below about 1kV, and the term
extra low voltage for what most of us would think of as low voltage - 50V and down.