On 16/04/2021 16:25, NY wrote:
"Peter Able" wrote in message
...
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?

P1, P2, P3, N, E

Telephones - well it is around here.

With the phone wires on (as far as I could see) the same brown porcelain
insulators as the 240 V mains wires?

This is the wiring https://goo.gl/maps/7TY9tJ2LNZfzEGE46 and
https://goo.gl/maps/YRgYsyz7K75p3KUZ6: the latter shows a separate phone
wire swapping from below the five mains wires on the nearest post to the
above them on the next post, which looks as if it could cause if the
insulated phone cable was repeatedly blown against the un-insulated
mains wires, eventually taking the phone insulation off and shorting the
mains wires.

It is an optical illusion the phone line is below the mains wiring (and
in prehistory the mains was probably insulated but not any more). Ours
failed by having strips of the rubber insulation fall off and short
adjacent phases in bad wet weather with much arcing and sparking.

The phone line goes from low position on an electric pole to a higher
phone pole set back from the electricity lines so there is no danger of
them rubbing together. Phone is below mains wiring on our poles.

My own village was wired about like this until the insulation fallign
off kept bring the entire network down. It was replaced by three core
aluminium conductors platted around a steel hawser down the middle.

The new wiring proved strong enough to resist a tree falling across it
although the supporting poles ended up like bananas and one side of the
street was disconnected from supply. I have a picture of it somewhere.
My hedge has still not quite recovered from the damage.

The poles now have little plaques on "unsafe: do not climb".

--
Regards,
Martin Brown