Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?


It's cheaper.

On Monday, 12 October 2020 at 11:26:10 UTC+1, Jack Harry Teesdale wrote:
On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

It's cheaper.
I saw that when they dug a trench through a local garden centre car park to get to a substation and was intrigued. No idea if it is plaited already on the drum as I never saw that but it looked too neat and regular to have been done on site.

Richard

On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

as he said. its cheaper, and you only need an outer when you need
additional protection on the outside, or to carry an earth potential..

--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

On 12/10/2020 11:32, Tricky Dicky wrote:
On Monday, 12 October 2020 at 11:26:10 UTC+1, Jack Harry Teesdale wrote:
On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

It's cheaper.
I saw that when they dug a trench through a local garden centre car park to get to a substation and was intrigued. No idea if it is plaited already on the drum as I never saw that but it looked too neat and regular to have been done on site.

Richard


I thought that was the aluminium stuff that is regularly used to replace
the 3-phase copper up on poles ?.

Is each conductor separately protected with a steel outer braid, SWA
fashion, or they just using physical depth plus a concrete cap to
protect it ?.

On Monday, 12 October 2020 10:13:39 UTC+1, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

Saw electricity supply to a new housing estate being laid the other week. Three lots of "twisted three" in a trench - with plenty of very hefty sealed junctions. All outer layers were red. Didn't see the actual covering process but suspect a bit of gravel then some concrete and asphalt.

On Monday, 12 October 2020 14:11:12 UTC+1, polygonum_on_google wrote:
On Monday, 12 October 2020 10:13:39 UTC+1, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

Saw electricity supply to a new housing estate being laid the other week.
Three lots of "twisted three" in a trench - with plenty of very hefty
sealed junctions. All outer layers were red. Didn't see the actual
covering process but suspect a bit of gravel then some concrete and asphalt.

There are some buried cables near here laid as two sets of three red cables
side by side. There is a buried oil pressurisation tank. Every few years
holes get dug as they look for oil leaks. I was told that these cables run
at 33kV but could be operated at 66kV.

John

On 12/10/2020 11:55, Andrew wrote:
On 12/10/2020 11:32, Tricky Dicky wrote:
On Monday, 12 October 2020 at 11:26:10 UTC+1, Jack Harry Teesdale wrote:
On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being
done to
cables at a nearby substation. Some of the old cables are being
extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

It's cheaper.
I saw that when they dug a trench through a local garden centre car
park to get to a substation and was intrigued. No idea if it is
plaited already on the drum as I never saw that but it looked too neat
and regular to have been done on site.

Richard


I thought that was the aluminium stuff that is regularly used to replace
the 3-phase copper up on poles ?.

Is each conductor separately protected with a steel outer braid, SWA
fashion, or they just using physical depth plus a concrete cap to
protect it ?.

Many UK utility company distribution cables are aluminium these days.

The cables are usually XLPE (cross linked polymer) insulated with a
layer of aluminium stranded armour for protection.

Some cable types incorporate a copper tape screen layer to provide a
earth fault current return path.

On 12/10/2020 16:39, Jack Harry Teesdale wrote:
On 12/10/2020 11:55, Andrew wrote:
On 12/10/2020 11:32, Tricky Dicky wrote:
On Monday, 12 October 2020 at 11:26:10 UTC+1, Jack Harry Teesdale wrote:
On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being
done to
cables at a nearby substation. Some of the old cables are being
extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

It's cheaper.
I saw that when they dug a trench through a local garden centre car
park to get to a substation and was intrigued. No idea if it is
plaited already on the drum as I never saw that but it looked too
neat and regular to have been done on site.

Richard


I thought that was the aluminium stuff that is regularly used to replace
the 3-phase copper up on poles ?.

Is each conductor separately protected with a steel outer braid, SWA
fashion, or they just using physical depth plus a concrete cap to
protect it ?.

Many UK utility company distribution cables are aluminium these days.

The cables are usually XLPE (cross linked polymer) insulated with a
layer of aluminium stranded armour for protection.

Some cable types incorporate a copper tape screen layer to provide a
earth fault current return path.

Aluminium armour doesn't seem to provide much protection, surely,
compared to steel armour ?

On 12/10/2020 18:08, Andrew wrote:
On 12/10/2020 16:39, Jack Harry Teesdale wrote:
On 12/10/2020 11:55, Andrew wrote:
On 12/10/2020 11:32, Tricky Dicky wrote:
On Monday, 12 October 2020 at 11:26:10 UTC+1, Jack Harry Teesdale
wrote:
On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being
done to
cables at a nearby substation. Some of the old cables are being
extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

It's cheaper.
I saw that when they dug a trench through a local garden centre car
park to get to a substation and was intrigued. No idea if it is
plaited already on the drum as I never saw that but it looked too
neat and regular to have been done on site.

Richard


I thought that was the aluminium stuff that is regularly used to replace
the 3-phase copper up on poles ?.

Is each conductor separately protected with a steel outer braid, SWA
fashion, or they just using physical depth plus a concrete cap to
protect it ?.

Many UK utility company distribution cables are aluminium these days.

The cables are usually XLPE (cross linked polymer) insulated with a
layer of aluminium stranded armour for protection.

Some cable types incorporate a copper tape screen layer to provide a
earth fault current return path.

Aluminium armour doesn't seem to provide much protection, surely,
compared to steel armour ?

Aluminium is cheaper and doesn't rust! Even the steel wire armour is
easily penetrated by JCB type diggers, so not really that different.

Pure convenience and easier to get them routed around existing
infrastructure?
Brian

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Note this Signature is meaningless.!
"JohnP" wrote in message
. ..
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

polygonum_on_google wrote:

"twisted three" in a trench - with plenty of very hefty sealed junctions. All outer layers were red.

I've noticed a lot of round black cable replaced with the red twisted
conductor cables in recent years

BS7870 Part 4 section 4.10 "Triplex" apparently