On Fri, 16 Apr 2021 18:46:38 +0100, "NY" wrote:

"charles" wrote in message
...
In article , Peter Able
wrote:
On 16/04/2021 15:57, NY wrote:
I'm used to seeing three-wire (three phases) overhead mains wiring from
poles along a street. Sometimes you get four-wire (three phases plus
neutral). Modern wiring is a single larger cable which is the three (or
four) wires twisted together. In each case, two wires (between two
phases, or one phase and neutral) go to each house, with a different
phase for each house or group of houses.

But I'm mystified about five-wire mains. As far as I could see, all
five wires were the same thickness and were each fastened to the same
type of insulator on the wooden poles - so probably not three-wire
mains and telephone.

What would the fifth wire be used for?

Telephones - well it is around here.

PA

In the UK you can't mix mains and telephone. 5 wire 3 phases, neutral &
earth.

What are the circumstances when overhead mains wiring has an extra earth
wire, rather than the earthing being done at each house? I've never seen it
before. Come to think of it, why do some installations have a neutral wire
and some don't - are there cases where the nett load is expected to be
unbalanced on the three phases, requiring an extra neutral?

Are you saying that telephone wires in the UK always require separate poles
and can't be carried on electricity poles?

I thought they picked up hum if they ran parallel to an electricity
cable.