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.
From the Sofa of Brian Gaff Reply address is active
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On Saturday, 18 March 2017 00:07:59 UTC, James Wilkinson Sword wrote:
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.
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.
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
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
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.
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
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.
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.
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.
5A maximum I assume. If you use 5A on average, you'd get a very big electricity bill.
Two blondes living in Oklahoma were sitting on a bench talking, and one blonde says to the other, "Which do you think is farther away... Florida or the moon?"
The other blonde turns and says "Helloooooooooo, can you see Florida ?????"
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).
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
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.
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
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