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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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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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#2
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How much current flows through pylons?
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 -- From the Sofa of Brian Gaff Reply address is active Remember, if you don't like where I post or what I say, you don't have to read my posts! :-) "James Wilkinson Sword" wrote in message news 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? |
#3
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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 |
#5
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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. |
#6
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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 |
#7
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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. |
#8
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How much current flows through pylons?
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#9
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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. -- Adam |
#10
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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. |
#11
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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. -- Those who want slavery should have the grace to name it by its proper 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. Ayn Rand. |
#12
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How much current flows through pylons?
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 -- ----- - This newsgroup posting comes to you directly from... The Sofa of Brian Gaff... Blind user, so no pictures please! "James Wilkinson Sword" wrote in message news 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? |
#13
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How much current flows through pylons?
"Brian Gaff" wrote in message
news 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. |
#14
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How much current flows through pylons?
"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). |
#15
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How much current flows through pylons?
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. |
#16
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How much current flows through pylons?
"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. 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. |
#17
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How much current flows through pylons?
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 |
#18
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How much current flows through pylons?
"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). |
#19
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How much current flows through pylons?
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.. |
#21
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How much current flows through pylons?
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#22
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How much current flows through pylons?
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 |
#23
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How much current flows through pylons?
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. -- "I am inclined to tell the truth and dislike people who lie consistently. This makes me unfit for the company of people of a Left persuasion, and all women" |
#24
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How much current flows through pylons?
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. -- "I am inclined to tell the truth and dislike people who lie consistently. This makes me unfit for the company of people of a Left persuasion, and all women" |
#25
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How much current flows through pylons?
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 -- "I am inclined to tell the truth and dislike people who lie consistently. This makes me unfit for the company of people of a Left persuasion, and all women" |
#26
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How much current flows through pylons?
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. -- Cheers Dave. |
#27
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How much current flows through pylons?
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. -- "I am inclined to tell the truth and dislike people who lie consistently. This makes me unfit for the company of people of a Left persuasion, and all women" |
#28
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How much current flows through pylons?
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. |
#29
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How much current flows through pylons?
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. |
#30
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How much current flows through pylons?
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. |
#31
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How much current flows through pylons?
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? -- If you feel tired, pull off at the motorway services -- Highway Code, UK. How's that going to help?!? |
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How much current flows through pylons?
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#33
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How much current flows through pylons?
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. -- 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 ?????" |
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How much current flows through pylons?
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. -- When a woman wears leather clothing, a man's heart beats quicker, his throat gets dry, he goes weak in the knees, and he begins to think irrationally. Ever wonder why? She smells like a new truck! |
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How much current flows through pylons?
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? -- Two cowboys are talking over a beer, discussing various sex positions. The first cowboy says his favorite position is "the rodeo". The other cowboy asks what the position is, and how to do it. The first cowboy says, "You tell your wife to get on the bed on all fours and then do it doggy style. Once things start to get under way and she's really enjoying it, lean forward, grab her by her hair and whisper in her ear, 'Your sister likes this position too.' Then try to hang on for 8 seconds". |
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How much current flows through pylons?
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. -- A father is someone who carries pictures where his money used to be. |
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How much current flows through pylons?
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". -- Went to the pub with my girlfriend last night. Locals were shouting "paedophile!" and other names at me, just because my girlfriend is 21 and I'm 50. It completely spoilt our 10th anniversary. |
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How much current flows through pylons?
On Sat, 18 Mar 2017 19:26:27 -0000, Harry Bloomfield wrote:
submitted this idea : 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.) Also remember it is a grid. Those are likely maximums and the actual current flow can be in either direction, depending upon where there is demand and what generating stations are online. Yes, I was just wondering what the capacity was. -- The squaw on the hippopotamus is equal to the sons of the squaws on the other two hides! |
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How much current flows through pylons?
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. -- Graham Nye news(a)thenyes.org.uk |
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How much current flows through pylons?
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 -- If I said you had a beautiful body, would you hold it against me? -- Monty Python, Episode 25 |
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