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Default How much current flows through pylons?

Despite extensive googling, there seems to be nothing that tells me how much current flows along wires on a national grid pylon. They only list voltages. Anybody know?
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Well it depends on the load one supposes. It also then depends on the
voltage on thewwires as the whole idea of using high voltages is to reduce
losses due to disipation when the system is under load.
The answer basically is there is no answer.
Might find more if you asked the max current of the one at xx to yy.
Brian

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"James Wilkinson Sword" wrote in message
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Despite extensive googling, there seems to be nothing that tells me how
much current flows along wires on a national grid pylon. They only list
voltages. Anybody know?



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Default How much current flows through pylons?

On Saturday, 18 March 2017 00:07:59 UTC, James Wilkinson Sword wrote:
Despite extensive googling, there seems to be nothing that tells me how much
current flows along wires on a national grid pylon. They only list voltages.
Anybody know?


A 400 kV National Grid circuit may carry 1 kA in each of its three phases, thus transmitting a power of 700 MW.
A 132 kV distribution circuit may carry 300 A in each of its three phases, thus transmitting a power of 70 MW.
An 11 kV distribution circuit may carry 150 A in each of its three phases, thus transmitting a power of 3 MW.
A 400 V final distribution circuit may carry 200 A in each of its three phases, thus transmitting a power of 150 kW.

(Remember, these voltages are phase-to-phase voltages, the phase-to-earth voltages are 1.73 times lower. Thus (400 kV/1.73) x 1kA x 3 = 700 MW.)

http://www.emfs.info/what/terminology/ (site maintained by National Grid)

[Pylon type] L12 is effectively the L6 replacement will take twin conductors up to 850mm2, but all aluminium conductor rather than the heavier steel cored kind formerly used.

http://www.gorge.org/pylons/structure.shtml

Owain


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Default How much current flows through pylons?

"newshound" wrote in message
o.uk...
On 3/18/2017 11:18 AM, wrote wrote:
Despite extensive googling, there seems to be nothing that tells me how
much
current flows along wires on a national grid pylon. They only list
voltages.
Anybody know?


A 400 kV National Grid circuit may carry 1 kA in each of its three phases,
thus transmitting a power of 700 MW.
A 132 kV distribution circuit may carry 300 A in each of its three phases,
thus transmitting a power of 70 MW.
An 11 kV distribution circuit may carry 150 A in each of its three phases,
thus transmitting a power of 3 MW.
A 400 V final distribution circuit may carry 200 A in each of its three
phases, thus transmitting a power of 150 kW.


200A per phase at 400V (240V phase-to-neutral) doesn't sound very high. We
have a 60 A "company fuse" and I presume our neighbours do too. With an
electric fire (3 KW), an electric shower (maybe 8 kW) and an electric oven
and hob (maybe 6 KW), you'd be getting towards that limit but still
remaining legal. Now imagine lots of people roundabout doing that. It
doesn't take many houses to run up 200 A - or a total of 600 A across all
three phases. How many houses are typically fed from a single feed from the
substation or 11 kV-to-400V pole-mounted transformer? What is the average
current that is assumed per house when sizing up the number of houses that
can be fed from one substation circuit? I presume it not the full 60A of the
company fuse rating.

And Supergrid pylons (400 and 275 kV) are normally double circuit, aren't
they? Three wires on each side of the "tree".


How much of the route from the power station to the consumer is redundant
multi-circuit? At one point, typically, does it change over to a given house
only being fed by one set of wires, and if that line develops a fault there
is no backup circuit?

Is there a backup route as far as the final substation that transforms to 11
kV or 400V, or is it higher up the chain?

I presume for maximum redundancy they try to use feeds from different places
rather than two sets of wires carried on the same pylons, in case an
accident takes out *all* the wires (both circuits).

I'm intrigued at the way house gets its electricity supply. There is
overhead mains on wooden poles (originally four separate wires, now a single
fat cable with four wires) and our house is the middle house of two adjacent
blocks of three houses. There is a single feed from the wooden poles to the
end of one block, and then four wires running along the back of one block,
overhead across the gap to the next block and along there, with each house
taking its feed from neutral and one of the three phases - I think no two
adjacent houses are on the same phase. I suppose this is less unsightly than
every one of the six houses having its own single-phase feed from the street
poles.






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Default How much current flows through pylons?

"NY" wrote in message
...

SNIP

How much of the route from the power station to the consumer is redundant
multi-circuit? At one point, typically, does it change over to a given
house only being fed by one set of wires, and if that line develops a fault
there is no backup circuit?

Is there a backup route as far as the final substation that transforms to
11 kV or 400V, or is it higher up the chain?

I presume for maximum redundancy they try to use feeds from different
places rather than two sets of wires carried on the same pylons, in case an
accident takes out *all* the wires (both circuits).

I'm intrigued at the way house gets its electricity supply. There is
overhead mains on wooden poles (originally four separate wires, now a
single fat cable with four wires) and our house is the middle house of two
adjacent blocks of three houses. There is a single feed from the wooden
poles to the end of one block, and then four wires running along the back
of one block, overhead across the gap to the next block and along there,
with each house taking its feed from neutral and one of the three phases -
I think no two adjacent houses are on the same phase. I suppose this is
less unsightly than every one of the six houses having its own single-phase
feed from the street poles.




They always used to rotate phases down a street, so (say) phase 1 - house
1, phase 2 - house 2, phase 3 - house 3, then phase 1 - street lighting,
phase 2 - house 4 and so on down the road to balance the load between
phases.

We have the 11 kV to 415 v transformer on our land and are the first 'drop'
of single phase at the farmhouse, but also take the three phase into the
barn at 160 amps per phase. No street lighting though round here. The 11 kV
can be fed from two points - we have an overhead HV line and an underground
HV cable, but normally only one is active.

Andrew

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Default How much current flows through pylons?

Andrew Mawson was thinking very hard :
They always used to rotate phases down a street, so (say) phase 1 - house 1,
phase 2 - house 2, phase 3 - house 3, then phase 1 - street lighting,
phase 2 - house 4 and so on down the road to balance the load between
phases.


So as to as best they can, balance the load on all three phases, so as
little current as possible appears on the neutral line.
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Default How much current flows through pylons?

On 18/03/2017 15:57, Andrew Mawson wrote:
"NY" wrote in message
...

SNIP

How much of the route from the power station to the consumer is
redundant multi-circuit? At one point, typically, does it change over
to a given house only being fed by one set of wires, and if that line
develops a fault there is no backup circuit?

Is there a backup route as far as the final substation that transforms
to 11 kV or 400V, or is it higher up the chain?

I presume for maximum redundancy they try to use feeds from different
places rather than two sets of wires carried on the same pylons, in
case an accident takes out *all* the wires (both circuits).

I'm intrigued at the way house gets its electricity supply. There is
overhead mains on wooden poles (originally four separate wires, now a
single fat cable with four wires) and our house is the middle house of
two adjacent blocks of three houses. There is a single feed from the
wooden poles to the end of one block, and then four wires running
along the back of one block, overhead across the gap to the next block
and along there, with each house taking its feed from neutral and one
of the three phases - I think no two adjacent houses are on the same
phase. I suppose this is less unsightly than every one of the six
houses having its own single-phase feed from the street poles.




They always used to rotate phases down a street, so (say) phase 1 -
house 1, phase 2 - house 2, phase 3 - house 3, then phase 1 - street
lighting, phase 2 - house 4 and so on down the road to balance the load
between phases.



Yep, and it's not uncommon to see that in multiples of houses. So you
may have 4 houses next to each other on phase one, the next 4 on phase 2
etc.

A far more common variant (on properties built in the late 1960's and
early 1970's) is house 1 and 2 on phase 1, house 3 and 4 on phase 2 and
house 5 and 6 on phase 3.




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Default How much current flows through pylons?

On Sat, 18 Mar 2017 12:05:12 +0000, NY wrote:

200A per phase at 400V (240V phase-to-neutral) doesn't sound very high.
We have a 60 A "company fuse" and I presume our neighbours do too. With
an electric fire (3 KW), an electric shower (maybe 8 kW) and an electric
oven and hob (maybe 6 KW), you'd be getting towards that limit but still
remaining legal. Now imagine lots of people roundabout doing that.


It's called Diversity. The DNO's know that everything will not be plugged
in at the same time, so their network will cope for the vast majority of
the time (and time has proven this, as there are very few blackouts
caused due to DNO substation fusing blowing).Short term overloads dont
stress the system too much, as can be seen on christmas day - when 50% of
houses have their ovens on etc - but 50% of them are gas,then the oven is
not on full power apart from the first 5 minutes, so the load isnt as
much as you think
I was told the typical demand for each house when the network is designed
is around 5 to 10 amps.That'd give 120 houses to one substation feed at 5
amps - that seems about right.


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Default How much current flows through pylons?

On 18/03/17 12:05, NY wrote:
200A per phase at 400V (240V phase-to-neutral) doesn't sound very high.
We have a 60 A "company fuse" and I presume our neighbours do too. With
an electric fire (3 KW), an electric shower (maybe 8 kW) and an electric
oven and hob (maybe 6 KW), you'd be getting towards that limit but still
remaining legal. Now imagine lots of people roundabout doing that. It
doesn't take many houses to run up 200 A - or a total of 600 A across
all three phases. How many houses are typically fed from a single feed
from the substation or 11 kV-to-400V pole-mounted transformer? What is
the average current that is assumed per house when sizing up the number
of houses that can be fed from one substation circuit? I presume it not
the full 60A of the company fuse rating.


Course not. Average power per household is 1-2KW.

And Supergrid pylons (400 and 275 kV) are normally double circuit,
aren't they? Three wires on each side of the "tree".


How much of the route from the power station to the consumer is
redundant multi-circuit? At one point, typically, does it change over to
a given house only being fed by one set of wires, and if that line
develops a fault there is no backup circuit?

Typically 11KV is run as a ring - it is here anyway, so the only single
point of failure is the 240V stuff from the local substation.

Is there a backup route as far as the final substation that transforms
to 11 kV or 400V, or is it higher up the chain?

I presume for maximum redundancy they try to use feeds from different
places rather than two sets of wires carried on the same pylons, in case
an accident takes out *all* the wires (both circuits).

As I said, round here 11KV is a ring.

I'm intrigued at the way house gets its electricity supply. There is
overhead mains on wooden poles (originally four separate wires, now a
single fat cable with four wires) and our house is the middle house of
two adjacent blocks of three houses. There is a single feed from the
wooden poles to the end of one block, and then four wires running along
the back of one block, overhead across the gap to the next block and
along there, with each house taking its feed from neutral and one of the
three phases - I think no two adjacent houses are on the same phase. I
suppose this is less unsightly than every one of the six houses having
its own single-phase feed from the street poles.





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name. They must face the full meaning of that which they are advocating
or condoning; the full, exact, specific meaning of collectivism, of its
logical implications, of the principles upon which it is based, and of
the ultimate consequences to which these principles will lead. They must
face it, then decide whether this is what they want or not.

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The actual answer of course is none it goes through the wires, but that
would be being pedantic.
Of course if like me you stood near a pylon when it was struck by
lightening you would see how well built they are!
Brian

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"James Wilkinson Sword" wrote in message
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Despite extensive googling, there seems to be nothing that tells me how
much current flows along wires on a national grid pylon. They only list
voltages. Anybody know?



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"Brian Gaff" wrote in message
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The actual answer of course is none it goes through the wires, but that
would be being pedantic.
Of course if like me you stood near a pylon when it was struck by
lightening you would see how well built they are!


I've never been near a pylon when it's been struck by lightning (*). I
wonder if it was the pylon itself or one of the phase wires that was struck.
I bet the bang is pretty impressive. The closest I've come was when a pylon
(maybe 66 or 132 kV) about 300 yards away was struck - there was a
ground-shaking bang and a very bright flash out of the window - much
brighter than normal lightning - and the power went off for a couple of
seconds and then came back on again as the circuit-breakers somewhere
upstream tried restoring power. I couldn't see any sign of blackened pylon
arm, so it may have been a strike on one of the phase wires.

Luckily I'd unplugged my PC a few moments before, as I noticed the storm
approaching - distant thunder got louder and the flash-to-bang time reduced
to a couple of seconds - so I escaped any damage.

Another storm, I wasn't quite so lucky: a minor flicker in the lights from a
fairly distant storm took out the power supply of my PC. As luck would have
it, I had a spare PSU on my desk which I keep in case any of my customers
have a faulty PSU, so I was able to swap it over. I'm quite proud of myself:
I have a weather station which updates its data in the log files every ten
minutes. The PC went down just after one reading and I had the PC back up
again, having swapped over the PSU, together with leads to each disk drive,
the CD drive, and the three leads to the motherboard, in time (just - it was
close!) for the next reading 10 minutes later. And probably about 2 minutes
of the time was taken up with the interminable time it takes my PC to boot
up and for the weather-station app to start reading data again.


(*) I have not-so-fond memories of cross-country running at school on a
route that took us under pylons. It was a really obnoxious route. You had to
endure the taunts of the local kids from other schools on the estate, then
run along a muddy, puddly unmade road, past the factory where they boiled up
animal carcases to make glue (trying not to puke at the smell), under the
fizzing pylon wires which often glowed a pretty mauve on a foggy day and
made your hair stand on end, and then try not to get savaged by the alsatian
guard dogs from the car breakers yard - and all of that was within about 1/4
mile. After that it got easier! https://goo.gl/maps/p1PNHJWtECk shows the
rusty girders which are all the remain of the glue factory, then the pylon
and then (to the left of where the car is parked) the place where the car
dump used to be. It all looks a lot less grotty than I remember it in the
mid 70s.

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"The Natural Philosopher" wrote in message
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How much of the route from the power station to the consumer is
redundant multi-circuit? At one point, typically, does it change over to
a given house only being fed by one set of wires, and if that line
develops a fault there is no backup circuit?

Typically 11KV is run as a ring - it is here anyway, so the only single
point of failure is the 240V stuff from the local substation.


Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm sitting I
can see the end of the 11 kV line and its transformer. Its 240V cables go
underground to houses on one side of the road (probably built in 1950s) and
then come above ground to 3-phase 240V overhead wires to the houses on the
other side of the road (1930s).

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NY has brought this to us :
Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm sitting I
can see the end of the 11 kV line and its transformer. Its 240V cables go
underground to houses on one side of the road (probably built in 1950s) and
then come above ground to 3-phase 240V overhead wires to the houses on the
other side of the road (1930s).


Are you sure it is 11Kv - more likely it will be 3.3Kv.


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"Harry Bloomfield" wrote in message
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NY has brought this to us :
Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm sitting I
can see the end of the 11 kV line and its transformer. Its 240V cables go
underground to houses on one side of the road (probably built in 1950s)
and
then come above ground to 3-phase 240V overhead wires to the houses on
the
other side of the road (1930s).


Are you sure it is 11Kv - more likely it will be 3.3Kv.


Ah, I wasn't aware that there was an intermediate distribution voltage
between 11kV and 240V. Are most power lines on pairs of wooden poles with
big glass insulators and pole-mounted transformers 3.3 rather than 11 kV?

This is the pole https://s22.postimg.org/n6x2dkkip/IMG_0456.jpg

I hadn't spotted the four horizontal wires in the foreground. I was wrong:
the 240V evidently goes underground to the back of just one terrace block
and then 3 phases and neutral runs between the three terrace blocks, with
alternating phases - same as in our older terraces on the other side of the
road from the 3.3 kV.

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On Sun, 19 Mar 2017 14:13:01 -0000, "NY" wrote:

"Harry Bloomfield" wrote in message
news
NY has brought this to us :
Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm sitting I
can see the end of the 11 kV line and its transformer. Its 240V cables go
underground to houses on one side of the road (probably built in 1950s)
and
then come above ground to 3-phase 240V overhead wires to the houses on
the
other side of the road (1930s).


Are you sure it is 11Kv - more likely it will be 3.3Kv.


Ah, I wasn't aware that there was an intermediate distribution voltage
between 11kV and 240V.


Wonder if H Bloomfield did a typo and meant 33Kv which is used
frequently . The supply to our farm was be 11Kv , where we are now is
also fed by 11Kv so to say it is more likely to be 33Kv or 11Kv would
need access to official records but also where you are gives a bit of
a clue, a few houses and a farm out in the sticks 11Kv but a more
densely populated area with some industry 33Kv.
There is some distribution done at a lower voltage usually in towns
and nowadays at 6.6Kv but some supplies that have been in place since
the 1920's or 30's may been slightly lower before things got
standardised.

G.Harman
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"NY" wrote in message
...
"The Natural Philosopher" wrote in message
news
How much of the route from the power station to the consumer is
redundant multi-circuit? At one point, typically, does it change over to
a given house only being fed by one set of wires, and if that line
develops a fault there is no backup circuit?

Typically 11KV is run as a ring - it is here anyway, so the only single
point of failure is the 240V stuff from the local substation.


Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V.


Ours that were done in the very early 70s are done like that.

Where I'm sitting I can see the end of the 11 kV line and its transformer.
Its 240V cables go underground to houses on one side of the road


The later subdivisions, what you lot call estates here have the 11KV
underground too, and the transformers stand on the ground, in big
metal cabinets about the size of a decent sized car, not quite as tall
as a van.

(probably built in 1950s) and then come above ground to 3-phase 240V
overhead wires to the houses on the other side of the road (1930s).


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NY has brought this to us :
Ah, I wasn't aware that there was an intermediate distribution voltage
between 11kV and 240V. Are most power lines on pairs of wooden poles with big
glass insulators and pole-mounted transformers 3.3 rather than 11 kV?


On wooden poles, I would suggest yes..
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On Sun, 19 Mar 2017 15:20:19 +0000, wrote:

Are you sure it is 11Kv - more likely it will be 3.3Kv.


Ah, I wasn't aware that there was an intermediate distribution

voltage
between 11kV and 240V.


Wonder if H Bloomfield did a typo and meant 33Kv which is used
frequently.


There are a few intermediate voltages but I don't think it's very
common and is probably only in places that have had a supply for
around a centuary...

Here the primary substation is fed by a 33 kV line and back up 11 kV
line.
I think the 33 kV orginates at Penrith, the 11 kV from the primary at
Little Selkeld. The 11 kV has a regulator in circuit a couple of
miles from the primary substation. Even with the regulator our
voltage wangs about all over the shop when the back up 11 kV is being
used. Rises to above 255 at night and drops to 225 ish during the
day. 240 to 245 is the normal range. It was complaining about the
over voltage that lead me to finding out the 11 kV was fed from
Little Selkeld, as they dropped a couple of hundred volts off it
there and things got better (only 253 overnight) but doing that
reduces everyone else fed from that line so it didn't stay like that.
Presumably the regulator is hitting an end stop at night...

From the primamry substation the 11 kV distribution is constructed as
a collection of half a dozen or so interconnected rings. These rings
are normally operated as spurs with an auto reclosure on each one
near the primary. Manual operated air swtches that are normally open
or normally closed enable any section of line to be isolated or fed
from either end. There are a number of spurs, some branched, that can
only be fed from one end. We are on the end of one that only feeds
us.

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On Sun, 19 Mar 2017 20:12:19 GMT, Harry Bloomfield
wrote:

expressed precisely :
Wonder if H Bloomfield did a typo and meant 33Kv which is used
frequently .


No, I meant 3.3Kv or 3Kv3.

Well that is a voltage I don't remember seeing anywhere.I'm off down
the local in minute where a the missus gets gardening tips from a
bloke who is always winning growing competitions often calls in.,He is
also a retired Linesman for what was Southern Electric, I'll ask him
if he knew of it any area. It's possibly a std that hung over in a
particular area or two from prenationalisation days .


So far as I am aware, all 11Kv and up is on
metal poles.


I'm genuinely surprised that you think that.
http://norpower.co.uk/services/11-33kv-wood-poles
Been in use donkeys years,the 11Kv that crossed our land on wood poles
went in 1958 and a couple of miles away the small Substation had 33Kv
wood pole lines feeding it as do 1000's of others .Many wood poles
have been replaced in recent times with new wooden ones a little
taller in a rolling programme to raise the height of lines above
fields as farm machinery has got taller.


http://norpower.co.uk/services/132-kv-woodpoles
http://www.wilsonfearnall.co.uk/new-...or-shropshire/
These are relatively recent development allowing wind farms easy
connection and network strengthening and it is understandable that
many will not be aware of them, the tall insulators in the trident
formation are the most obvious clue.

G.Harman
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On 19/03/17 13:14, Harry Bloomfield wrote:
NY has brought this to us :
Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm sitting I
can see the end of the 11 kV line and its transformer. Its 240V cables go
underground to houses on one side of the road (probably built in
1950s) and
then come above ground to 3-phase 240V overhead wires to the houses on
the
other side of the road (1930s).


Are you sure it is 11Kv - more likely it will be 3.3Kv.

Never heard of 3.3kV - all the overheads here are 11KV apart from the
big one at 33kV.

Oh and the 240v stuff of course.


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On 19/03/17 14:13, NY wrote:
"Harry Bloomfield" wrote in message
news
NY has brought this to us :
Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm
sitting I
can see the end of the 11 kV line and its transformer. Its 240V
cables go
underground to houses on one side of the road (probably built in
1950s) and
then come above ground to 3-phase 240V overhead wires to the houses
on the
other side of the road (1930s).


Are you sure it is 11Kv - more likely it will be 3.3Kv.


Ah, I wasn't aware that there was an intermediate distribution voltage
between 11kV and 240V.


There arent.

Are most power lines on pairs of wooden poles
with big glass insulators and pole-mounted transformers 3.3 rather than
11 kV?

No.

This is the pole https://s22.postimg.org/n6x2dkkip/IMG_0456.jpg

I hadn't spotted the four horizontal wires in the foreground. I was
wrong: the 240V evidently goes underground to the back of just one
terrace block and then 3 phases and neutral runs between the three
terrace blocks, with alternating phases - same as in our older terraces
on the other side of the road from the 3.3 kV.



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On 19/03/17 20:08, Harry Bloomfield wrote:
NY has brought this to us :
Ah, I wasn't aware that there was an intermediate distribution voltage
between 11kV and 240V. Are most power lines on pairs of wooden poles
with big glass insulators and pole-mounted transformers 3.3 rather
than 11 kV?


On wooden poles, I would suggest yes..


No.
33KV is wooden pole stuff as is 11KV and the odd 240V

132kV is where the lattice towers start


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On Sun, 19 Mar 2017 20:12:19 GMT, Harry Bloomfield wrote:

No, I meant 3.3Kv or 3Kv3. So far as I am aware, all 11Kv and up is on
metal poles.


All the 11 kV feed and distribution and the 33 kV feed is on wooden
poles around here.

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On 19/03/17 20:12, Harry Bloomfield wrote:
expressed precisely :
Wonder if H Bloomfield did a typo and meant 33Kv which is used
frequently .


No, I meant 3.3Kv or 3Kv3. So far as I am aware, all 11Kv and up is on
metal poles.

Completely wrong

There is no 3.3kV

up to 33KV is on wooden poles

Next step up from 240V is 11KV 3 ph.

educate yourself

http://www.templar.co.uk/downloads/E...troduction.pdf

They can use what ever is the most cost effective/efficient for the load
and distance involved.



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It happens that The Natural Philosopher formulated :
Completely wrong

There is no 3.3kV


No sorry, you are wrong. I have used it many times on large motors.
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Harry Bloomfield wrote
NY wrote


Ah, I wasn't aware that there was an intermediate distribution voltage
between 11kV and 240V. Are most power lines on pairs of wooden poles with
big glass insulators and pole-mounted transformers 3.3 rather than 11 kV?


On wooden poles, I would suggest yes..


Ours were mostly on wooden poles when
they first went in and are definitely 11Kv.

The pole is irrelevant, it's the insulators that matter, trivial at 11KV.

We don't have any 3.3Kv distribution at all.

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On 3/19/2017 4:59 PM, Dave Liquorice wrote:
On Sun, 19 Mar 2017 20:12:19 GMT, Harry Bloomfield wrote:

No, I meant 3.3Kv or 3Kv3. So far as I am aware, all 11Kv and up is on
metal poles.


All the 11 kV feed and distribution and the 33 kV feed is on wooden
poles around here.

They're wooden in my area, too.


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On Sun, 19 Mar 2017 06:26:29 -0000, ARW wrote:

On 18/03/2017 15:57, Andrew Mawson wrote:
"NY" wrote in message
...

SNIP

How much of the route from the power station to the consumer is
redundant multi-circuit? At one point, typically, does it change over
to a given house only being fed by one set of wires, and if that line
develops a fault there is no backup circuit?

Is there a backup route as far as the final substation that transforms
to 11 kV or 400V, or is it higher up the chain?

I presume for maximum redundancy they try to use feeds from different
places rather than two sets of wires carried on the same pylons, in
case an accident takes out *all* the wires (both circuits).

I'm intrigued at the way house gets its electricity supply. There is
overhead mains on wooden poles (originally four separate wires, now a
single fat cable with four wires) and our house is the middle house of
two adjacent blocks of three houses. There is a single feed from the
wooden poles to the end of one block, and then four wires running
along the back of one block, overhead across the gap to the next block
and along there, with each house taking its feed from neutral and one
of the three phases - I think no two adjacent houses are on the same
phase. I suppose this is less unsightly than every one of the six
houses having its own single-phase feed from the street poles.




They always used to rotate phases down a street, so (say) phase 1 -
house 1, phase 2 - house 2, phase 3 - house 3, then phase 1 - street
lighting, phase 2 - house 4 and so on down the road to balance the load
between phases.



Yep, and it's not uncommon to see that in multiples of houses. So you
may have 4 houses next to each other on phase one, the next 4 on phase 2
etc.

A far more common variant (on properties built in the late 1960's and
early 1970's) is house 1 and 2 on phase 1, house 3 and 4 on phase 2 and
house 5 and 6 on phase 3.


I wonder if anyone's ever borrowed their neighbour's electricity when theirs is off, only to find it coming back on and joined phase 1 and 2 together with a big bang?

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On Sun, 19 Mar 2017 07:19:45 -0000, wrote:

On Sat, 18 Mar 2017 12:05:12 +0000, NY wrote:

200A per phase at 400V (240V phase-to-neutral) doesn't sound very high.
We have a 60 A "company fuse" and I presume our neighbours do too. With
an electric fire (3 KW), an electric shower (maybe 8 kW) and an electric
oven and hob (maybe 6 KW), you'd be getting towards that limit but still
remaining legal. Now imagine lots of people roundabout doing that.


It's called Diversity. The DNO's know that everything will not be plugged
in at the same time, so their network will cope for the vast majority of
the time (and time has proven this, as there are very few blackouts
caused due to DNO substation fusing blowing).Short term overloads dont
stress the system too much, as can be seen on christmas day - when 50% of
houses have their ovens on etc - but 50% of them are gas,then the oven is
not on full power apart from the first 5 minutes, so the load isnt as
much as you think


All very well as long as there's a suitable fuse. But when diversity is used in case of say a double mains socket in your house only taking 20 amps, but the fuse protecting it is 30A, you get fires.

I was told the typical demand for each house when the network is designed
is around 5 to 10 amps.That'd give 120 houses to one substation feed at 5
amps - that seems about right.


5A maximum I assume. If you use 5A on average, you'd get a very big electricity bill.

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On Sun, 19 Mar 2017 08:54:52 -0000, The Natural Philosopher wrote:

On 18/03/17 12:05, NY wrote:
200A per phase at 400V (240V phase-to-neutral) doesn't sound very high.
We have a 60 A "company fuse" and I presume our neighbours do too. With
an electric fire (3 KW), an electric shower (maybe 8 kW) and an electric
oven and hob (maybe 6 KW), you'd be getting towards that limit but still
remaining legal. Now imagine lots of people roundabout doing that. It
doesn't take many houses to run up 200 A - or a total of 600 A across
all three phases. How many houses are typically fed from a single feed
from the substation or 11 kV-to-400V pole-mounted transformer? What is
the average current that is assumed per house when sizing up the number
of houses that can be fed from one substation circuit? I presume it not
the full 60A of the company fuse rating.


Course not. Average power per household is 1-2KW.


Continuously? That's way too much. Think what your bill would be.

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On Sun, 19 Mar 2017 13:02:27 -0000, NY wrote:

"The Natural Philosopher" wrote in message
news
How much of the route from the power station to the consumer is
redundant multi-circuit? At one point, typically, does it change over to
a given house only being fed by one set of wires, and if that line
develops a fault there is no backup circuit?

Typically 11KV is run as a ring - it is here anyway, so the only single
point of failure is the 240V stuff from the local substation.


Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm sitting I
can see the end of the 11 kV line and its transformer. Its 240V cables go
underground to houses on one side of the road (probably built in 1950s) and
then come above ground to 3-phase 240V overhead wires to the houses on the
other side of the road (1930s).


I thought nowadays everything went underground, yet a new lot of houses across the road from me have overhead telephone cables. Why is this?

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On Sun, 19 Mar 2017 15:23:28 -0000, Tim Streater wrote:

In article ,
wrote:

On Sun, 19 Mar 2017 14:13:01 -0000, "NY" wrote:

"Harry Bloomfield" wrote in message
news NY has brought this to us :
Out here in a North Yorkshire village there seem to be 11 kV spurs, each
with a pole-mounted transformer to step down to 240V. Where I'm sitting I
can see the end of the 11 kV line and its transformer. Its 240V cables go
underground to houses on one side of the road (probably built in 1950s)
and then come above ground to 3-phase 240V overhead wires to the houses
on the other side of the road (1930s).

Are you sure it is 11Kv - more likely it will be 3.3Kv.

Ah, I wasn't aware that there was an intermediate distribution voltage
between 11kV and 240V.


Wonder if H Bloomfield did a typo and meant 33Kv which is used
frequently.


I wondered that too but don't know enough about power distribution.

When I first saw this thread title, however, I assumed it was talking
about how much leakage there was to earth from a pylon.


I thought it sounded a little ambiguous when I wrote it. Probably quite a bit, as if its raining, you can even feel it coming through the air.

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On Sun, 19 Mar 2017 20:54:35 -0000, Dave Liquorice wrote:

On Sun, 19 Mar 2017 15:20:19 +0000, wrote:

Are you sure it is 11Kv - more likely it will be 3.3Kv.

Ah, I wasn't aware that there was an intermediate distribution

voltage
between 11kV and 240V.


Wonder if H Bloomfield did a typo and meant 33Kv which is used
frequently.


There are a few intermediate voltages but I don't think it's very
common and is probably only in places that have had a supply for
around a centuary...

Here the primary substation is fed by a 33 kV line and back up 11 kV
line.
I think the 33 kV orginates at Penrith, the 11 kV from the primary at
Little Selkeld. The 11 kV has a regulator in circuit a couple of
miles from the primary substation. Even with the regulator our
voltage wangs about all over the shop when the back up 11 kV is being
used. Rises to above 255 at night and drops to 225 ish during the
day. 240 to 245 is the normal range. It was complaining about the
over voltage that lead me to finding out the 11 kV was fed from
Little Selkeld, as they dropped a couple of hundred volts off it
there and things got better (only 253 overnight) but doing that
reduces everyone else fed from that line so it didn't stay like that.
Presumably the regulator is hitting an end stop at night...

From the primamry substation the 11 kV distribution is constructed as
a collection of half a dozen or so interconnected rings. These rings
are normally operated as spurs with an auto reclosure on each one
near the primary. Manual operated air swtches that are normally open
or normally closed enable any section of line to be isolated or fed
from either end. There are a number of spurs, some branched, that can
only be fed from one end. We are on the end of one that only feeds
us.


Did you get anywhere with your complaint? I get 241V to 256V, which I consider very poor since 230V is supposed to be the normal. It's enough to regularly make my UPS put an overvoltage warning light on and step it down itself. When I phoned them, they sent someone out in 30 minutes and sounded worried on the phone, yet when the electrician arrived and confirmed my voltage readings, he said "within legal limits, nothing we can do, although if I was in charge I'd step it down a level".

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On 2017-03-19 21:39, Harry Bloomfield wrote:
It happens that The Natural Philosopher formulated :
Completely wrong

There is no 3.3kV


No sorry, you are wrong. I have used it many times on large motors.


Were they being supplied by on-site transformers or local generators?
The discussion is about the distribution network which seems to skip
3.3 kV and starts at 11 kV.



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I've seen a pylon with heavy snow on the wires. The phases got close enough to arc.


On Sun, 19 Mar 2017 10:20:52 -0000, Brian Gaff wrote:

The actual answer of course is none it goes through the wires, but that
would be being pedantic.
Of course if like me you stood near a pylon when it was struck by
lightening you would see how well built they are!
Brian



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