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Electricity: 3 phase query
Hi gang,
AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right? cheers. |
Electricity: 3 phase query
Oh, and before some helpful soul offers up a practical solution, such as "get yerself a phase converter, mate, it's a lot cheaper" I should just point out that I'm NOT looking for solutions, here, I'm simply enquiring as to whether my understanding of the basic situation is correct or not. Thanks!
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Electricity: 3 phase query
On Sun, 7 Jul 2013 06:03:20 -0700 (PDT),
wrote: Oh, and before some helpful soul offers up a practical solution, such as "get yerself a phase converter, mate, it's a lot cheaper" I should just point out that I'm NOT looking for solutions, here, I'm simply enquiring as to whether my understanding of the basic situation is correct or not. Thanks! From a legal, technical or practical angle? AB |
Electricity: 3 phase query
On Sunday, 7 July 2013 15:08:12 UTC+2, Archibald wrote:
On Sun, 7 Jul 2013 06:03:20 -0700 (PDT), wrote: Oh, and before some helpful soul offers up a practical solution, such as "get yerself a phase converter, mate, it's a lot cheaper" I should just point out that I'm NOT looking for solutions, here, I'm simply enquiring as to whether my understanding of the basic situation is correct or not. Thanks! From a legal, technical or practical angle? AB Er, technical and theoretical. I'm already aware that the most cost-effective practical solution is to hook up a phase converter to the distribution board via its own spur and that's what I'll probably end up doing. |
Electricity: 3 phase query
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Electricity: 3 phase query
It's curious. I've been heavily into electronics for decades yet nothing I've learned it seems, is relevant to domestic/industrial electric installations.
Though I'm intimately acquainted with the concept of phase, phase-shift and know the difference between current, voltage and power inside-out I'm still struggling to get to grips with this 'macro' stuff. These two fields are like chalk and cheese. I suppose an electrician would be equally perplexed if required to calculate the output impedance of a buffer/current-amplifier stage. :-/ |
Electricity: 3 phase query
wrote :
Hi gang, AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right? cheers. The basic numbers in the UK are 415v 3Ph. 240v single phase = 240v from any of the three phases, to neutral. 415v as measured from any phase aay of the other two. If you have 1ph + N, you are lacking two more phases to make a 3ph supply. -- Regards, Harry (M1BYT) (L) http://www.ukradioamateur.co.uk |
Electricity: 3 phase query
I mean they're clearly two different disciples entirely. In my typically millivolt/milliamp world, we don't have to contend with forces sufficient to rip a machine's internals to pieces as you do with power engineering, so the need for nice, smooth 3 phase supplies simply doesn't arise in the first place!
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Electricity: 3 phase query
Right, Harry. So with only two live phases you'd have your 415V potential difference alright, but it would be effectively unusable?
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Electricity: 3 phase query
On 07/07/2013 15:30, Harry Bloomfield wrote:
.... The basic numbers in the UK are 415v 3Ph. 240v single phase = 240v from any of the three phases, to neutral. 415v as measured from any phase aay of the other two.... Since 2003, it has been 400v and 230v, but with wider tolerances, so that neither we nor any other EU country had to make any change to existing equipment. Colin Bignell |
Electricity: 3 phase query
On Sunday, 7 July 2013 17:22:17 UTC+2, Nightjar wrote:
On 07/07/2013 15:30, Harry Bloomfield wrote: ... The basic numbers in the UK are 415v 3Ph. 240v single phase = 240v from any of the three phases, to neutral. 415v as measured from any phase aay of the other two.... Since 2003, it has been 400v and 230v, but with wider tolerances, so that neither we nor any other EU country had to make any change to existing equipment. Colin Bignell I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources. |
Electricity: 3 phase query
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Electricity: 3 phase query
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Electricity: 3 phase query
If you pay them, I should imagine, but if its industrial, then you might
have the gods of the council down for some business rates. Brian -- From the Bed of Brian Gaff. The email is valid as Blind user. wrote in message ... Hi gang, AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right? cheers. |
Electricity: 3 phase query
"John Williamson" wrote in message ... wrote: I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources. One problem is the huge installed base of equipment, including cable that is rated at the current voltages. Current insulation standards sometimes stuggle with the current voltages, shown by exploding cables as frequently reported in this newsgroup. Another reason is that along every street in the country is a set of three cables carrying the current voltages of 230V to earth, and 400V (+-) between them. To have 800V available, the powers that be would need to run new cables from new substations to only those users wanting 800V. Another way to save money on the grid would be to increase the frequency, allowing the use of smaller transformers for the same power. The same objections apply, although aerospace applications often use 400Hz AC for this reason. -- Tciao for Now! John. Trouble is even though substation efficiency would increase, your main transmission line losses will increase dramatically due to skin effect. It is still significant even at 50Hz. Andy |
Electricity: 3 phase query
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Electricity: 3 phase query
Andy Bartlett wrote:
"John Williamson" wrote in message Another way to save money on the grid would be to increase the frequency, allowing the use of smaller transformers for the same power. The same objections apply, although aerospace applications often use 400Hz AC for this reason. Trouble is even though substation efficiency would increase, your main transmission line losses will increase dramatically due to skin effect. It is still significant even at 50Hz. Conflicting requirements. DC is best for long distance transmission, and HF AC for smaller transformers...... It's Edison vs. Westinghouse all over again. Grin Could this be the reason why we use 50 - 60 Hz worldwide, as the best compromise for a national grid? -- Tciao for Now! John. |
Electricity: 3 phase query
On Sunday, 7 July 2013 19:07:50 UTC+2, Andrew Gabriel wrote:
In article , writes: I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources. When you plot all the costs against each other (e.g. conductor costs, insulator costs, switchgear costs, etc) with a very broad brush, you tend to find the optimum is around 1000V per mile over which you are transporting the electricity. So 240V is good for up to 1/4 mile runs (i.e. distance from substation), and 415V (same thing strung as 3-phase) can go a bit further with a roughly balanced load. So between villages, you might want various mixtures of, say, 1000V to 5000V, but then the next factor comes into play - the cost of conversion, and you don't want to do that too many times. Also, standardisation - let's stick to some specific voltages so we don't need loads of different transformer models, cable insulations, etc. We use 11,000 V as the voltage between most substations, and the next one up is 33,000V, these being good for transporting power around 11 and 33 miles respectively. The actual power carried also has to be factored in, and you might well get a shorter 33kV run where large amounts of power are required, or generated to be transported to the grid. 132kV, 275kV, and 400kV are used for transporting power over longer distances across the country, particularly as generation increasingly moved further away from consumption. (There may still be the odd 66kV line, but most of these were phased out as the National Grid was constructed.) -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] You see a lot of 3 wire transmission lines across the countryside. The lines are spaced about a meter apart and are supported by relatively close-to-the-ground wooden poles which aren't dissimilar to telegraph poles in appearance. You could reach them with a fishing rod they're that low in some places. I saw some hapless tree surgeon lop off a branch once that landed across two of these wires. Two little fires ignited at the contact points. Didn't look anything special at first. I expected an upstream breaker somewhere to activate and shut off the current, but that didn't happen. The fires grew rapidly and within one minute at the most there was the most *enormous* flash and ***BANG*** and everything then fell earily silent. It was one of the most spectacular things I've ever witnessed. Turned out the power to a couple of hundred thousand homes had been lost as a result. Would this have been one of your 33,000V lines? The homes affected were as far away as 35 miles from the incident, btw. |
Electricity: 3 phase query
wrote in message
... You see a lot of 3 wire transmission lines across the countryside. The lines are spaced about a meter apart and are supported by relatively close-to-the-ground wooden poles which aren't dissimilar to telegraph poles in appearance. You could reach them with a fishing rod they're that low in some places. I saw some hapless tree surgeon lop off a branch once that landed across two of these wires. Two little fires ignited at the contact points. Didn't look anything special at first. I expected an upstream breaker somewhere to activate and shut off the current, but that didn't happen. The fires grew rapidly and within one minute at the most there was the most *enormous* flash and ***BANG*** and everything then fell earily silent. It was one of the most spectacular things I've ever witnessed. Turned out the power to a couple of hundred thousand homes had been lost as a result. Would this have been one of your 33,000V lines? The homes affected were as far away as 35 miles from the incident, btw. Almost certainly 11kV on lines as you describe AWEM |
Electricity: 3 phase query
On 07/07/2013 18:19, John Williamson wrote:
Andy Bartlett wrote: "John Williamson" wrote in message Another way to save money on the grid would be to increase the frequency, allowing the use of smaller transformers for the same power. The same objections apply, although aerospace applications often use 400Hz AC for this reason. Trouble is even though substation efficiency would increase, your main transmission line losses will increase dramatically due to skin effect. It is still significant even at 50Hz. Conflicting requirements. DC is best for long distance transmission, and HF AC for smaller transformers...... It's Edison vs. Westinghouse all over again. Grin Or, in Britain, Crompton, Kelvin and Hopkinson v Ferranti, Mordley and Thompson. Could this be the reason why we use 50 - 60 Hz worldwide, as the best compromise for a national grid? Possibly something to do with 40Hz being about the minimum frequency at which flicker was not noticeable to most people with early incandescent lamps. There being a limited number of manufacturers in the world making generating equipment was probably also a factor. In Britain, in 1930, there were 15 different AC frequencies in use, from 25Hz to 100Hz, but 81% of all generation was at 50Hz. Standardisation cost £17.5 million. Colin Bignell |
Electricity: 3 phase query
On 07/07/2013 19:29, Nightjar wrote:
Standardisation cost £17.5 million. Interesting to consider the cost of not standardising would have been. -- Rod |
Electricity: 3 phase query
On Sunday, 7 July 2013 18:58:22 UTC+2, Bob Minchin wrote:
wrote: I mean they're clearly two different disciples entirely. In my typically millivolt/milliamp world, we don't have to contend with forces sufficient to rip a machine's internals to pieces as you do with power engineering, so the need for nice, smooth 3 phase supplies simply doesn't arise in the first place! I've found that most sparks I talk to don't have an in depth understanding of the subject. They are taught largely by rote both in college and as apprentices. They know all the how but very little why. There are exceptions naturally. My background like yours is in electronics but I've learned to adapt over the years. Bob I think you may be right. A recently qualified young electrician told me, in regards to electrical safety, that "even just a few megaohms can kill you.." I shuddered at the time, but feel much less alarmed now in the light of your remarks. |
Electricity: 3 phase query
On 07/07/2013 19:15, Andrew Mawson wrote:
wrote in message ... You see a lot of 3 wire transmission lines across the countryside. The lines are spaced about a meter apart and are supported by relatively close-to-the-ground wooden poles which aren't dissimilar to telegraph poles in appearance. You could reach them with a fishing rod they're that low in some places. I saw some hapless tree surgeon lop off a branch once that landed across two of these wires. Two little fires ignited at the contact points. Didn't look anything special at first. I expected an upstream breaker somewhere to activate and shut off the current, but that didn't happen. The fires grew rapidly and within one minute at the most there was the most *enormous* flash and ***BANG*** and everything then fell earily silent. It was one of the most spectacular things I've ever witnessed. Turned out the power to a couple of hundred thousand homes had been lost as a result. Would this have been one of your 33,000V lines? The homes affected were as far away as 35 miles from the incident, btw. Almost certainly 11kV on lines as you describe AWEM Agreed, and certainly not serving 200,000 homes unless it caused a trip in one of the much higher voltage lines, which I would have thought was unlikely. It went quiet because a breaker did operate, but only once there was enough ionisation from the fire to allow an arc between phases or from phase to ground. Perhaps a few hundred amps? Which is a few megawatts, maybe 1000 homes? |
Electricity: 3 phase query
On 07/07/2013 18:19, John Williamson wrote:
Andy Bartlett wrote: "John Williamson" wrote in message Another way to save money on the grid would be to increase the frequency, allowing the use of smaller transformers for the same power. The same objections apply, although aerospace applications often use 400Hz AC for this reason. Trouble is even though substation efficiency would increase, your main transmission line losses will increase dramatically due to skin effect. It is still significant even at 50Hz. Conflicting requirements. DC is best for long distance transmission, and HF AC for smaller transformers...... It's Edison vs. Westinghouse all over again. Grin Could this be the reason why we use 50 - 60 Hz worldwide, as the best compromise for a national grid? Apart from skin effect, 50-60 Hz keeps the generators simple: two poles per phase at 3000 rpm or occasionally 4 poles at 1500 for 50 Hz. You can't speed up big (500-650 MW) the generators significantly because you are close to the strength limits of suitable steel. You have conversion losses if you try to increase the frequencies with electronics. The losses in DC converters at each end of a DC link (like the interconnectors under the English Channel are offset by reductions in transmission loss. |
Electricity: 3 phase query
On Sunday 07 July 2013 19:15 Andrew Mawson wrote in uk.d-i-y:
wrote in message ... You see a lot of 3 wire transmission lines across the countryside. The lines are spaced about a meter apart and are supported by relatively close-to-the-ground wooden poles which aren't dissimilar to telegraph poles in appearance. You could reach them with a fishing rod they're that low in some places. I saw some hapless tree surgeon lop off a branch once that landed across two of these wires. Two little fires ignited at the contact points. Didn't look anything special at first. I expected an upstream breaker somewhere to activate and shut off the current, but that didn't happen. The fires grew rapidly and within one minute at the most there was the most *enormous* flash and ***BANG*** and everything then fell earily silent. It was one of the most spectacular things I've ever witnessed. Turned out the power to a couple of hundred thousand homes had been lost as a result. Would this have been one of your 33,000V lines? The homes affected were as far away as 35 miles from the incident, btw. Almost certainly 11kV on lines as you describe AWEM Dunno - the Robertsbridge overhead feeders are 33kV (it says so on some of the warning labels) and they are wooden poles, lines fairly close, low down. -- Tim Watts Personal Blog: http://squiddy.blog.dionic.net/ http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage Reading this on the web? See: http://wiki.diyfaq.org.uk/index.php?title=Usenet |
Electricity: 3 phase query
"John Williamson" wrote in message ... wrote: I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources. One problem is the huge installed base of equipment, including cable that is rated at the current voltages. Current insulation standards sometimes stuggle with the current voltages, shown by exploding cables as frequently reported in this newsgroup. Another reason is that along every street in the country is a set of three cables carrying the current voltages of 230V to earth, and 400V (+-) between them. To have 800V available, the powers that be would need to run new cables from new substations to only those users wanting 800V. Another way to save money on the grid would be to increase the frequency, allowing the use of smaller transformers for the same power. The same objections apply, although aerospace applications often use 400Hz AC for this reason. In days of yore as the national grid was being created, the were auto trnasformers between areas of different local voltages as a temporary thing. The electricity boards were responsible for collecting up all appliances and converting to the new voltage. Vast job even back then. Pre and post war. There would be no save for higher frequency in fact there would be increased iron or magnetic losses. Power is realated to voltage and in-phase component of the current only. The reason aircraft run on high frequency is that electric motors/transformers can be made much smaller and lighter because more power can be transmitted through any magnetic circuit by increasing the frequency. However they are far less efficient. Cable sizes are unaffected. 50 Hz is not the optimum frequency either. The Yanks have it right, 60Hz is optimum. If anything, we may go to DC in the future. Makes a lot more sense these days. I remeber helping to remove DC stuff back in the 60's. And put some in. It was the induction motor that did it. Mostly it was in places that got their initial electricity from coal mine/factory power houses. We will have come full circle. |
Electricity: 3 phase query
On Sunday, 7 July 2013 18:07:50 UTC+1, Andrew Gabriel wrote:
In article , writes: I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources. 690V (400V to neutral) three-phase is used in some countries, suitably-wound motors can be used at 400V delta or 690V star, so easing standardisation, maybe we should consider it. 132kV, 275kV, and 400kV are used for transporting power over longer distances across the country, particularly as generation increasingly moved further away from consumption. (There may still be the odd 66kV line, but most of these were phased out as the National Grid was constructed.) -- Andrew Gabriel Actually there's still quite a bit of 66kV, it's been established in North-East England from the time of the 'Newcastle-on-Tyne Electric Supply Co' who built a regional grid between the wars, also for underground cables in London where 33kV isn't enough and 132kV cables would be too expensive. |
Electricity: 3 phase query
It went quiet because a breaker did operate, but only once there was enough ionisation from the fire to allow an arc between phases or from phase to ground. Perhaps a few hundred amps? Which is a few megawatts, maybe 1000 homes? Nope. Definitely a couple of hundred thousand. I should, however, point out that this was back in the late 70s, so it's possible they've reduced the voltages these lines are permitted to carry since then. |
Electricity: 3 phase query
On Sunday, 7 July 2013 21:25:16 UTC+2, Tim Watts wrote:
On Sunday 07 July 2013 19:15 Andrew Mawson wrote in uk.d-i-y: wrote in message ... You see a lot of 3 wire transmission lines across the countryside. The lines are spaced about a meter apart and are supported by relatively close-to-the-ground wooden poles which aren't dissimilar to telegraph poles in appearance. You could reach them with a fishing rod they're that low in some places. I saw some hapless tree surgeon lop off a branch once that landed across two of these wires. Two little fires ignited at the contact points. Didn't look anything special at first. I expected an upstream breaker somewhere to activate and shut off the current, but that didn't happen. The fires grew rapidly and within one minute at the most there was the most *enormous* flash and ***BANG*** and everything then fell earily silent. It was one of the most spectacular things I've ever witnessed. Turned out the power to a couple of hundred thousand homes had been lost as a result. Would this have been one of your 33,000V lines? The homes affected were as far away as 35 miles from the incident, btw. Almost certainly 11kV on lines as you describe AWEM Dunno - the Robertsbridge overhead feeders are 33kV (it says so on some of the warning labels) and they are wooden poles, lines fairly close, low down. -- Tim Watts Personal Blog: http://squiddy.blog.dionic.net/ http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage Reading this on the web? See: http://wiki.diyfaq.org.uk/index.php?title=Usenet Wow! That's precisely the line I was talking about!!! |
Electricity: 3 phase query
In article , harryagain
wrote: "John Williamson" wrote in message ... wrote: I don't really understand why we don't go for 3 phase at say 800V. Let's face it: even 230V is well into the lethal zone so going higher isn't going to be any more dangerous. Plus 800 is still low enough not to arc or flashover - given remotely adequate insulation. And just think of the saving in terms of conductor! Given the price of copper (notwithstanding it's slipped back lately) I'd have thought pushing up the supply voltages would be obvious thing to do from the pov of conserving natural resources. One problem is the huge installed base of equipment, including cable that is rated at the current voltages. Current insulation standards sometimes stuggle with the current voltages, shown by exploding cables as frequently reported in this newsgroup. Another reason is that along every street in the country is a set of three cables carrying the current voltages of 230V to earth, and 400V (+-) between them. To have 800V available, the powers that be would need to run new cables from new substations to only those users wanting 800V. Another way to save money on the grid would be to increase the frequency, allowing the use of smaller transformers for the same power. The same objections apply, although aerospace applications often use 400Hz AC for this reason. In days of yore as the national grid was being created, the were auto trnasformers between areas of different local voltages as a temporary thing. The electricity boards were responsible for collecting up all appliances and converting to the new voltage. Vast job even back then. Pre and post war. certainly up to 1962, Cambridge town was supplied wth 200v mains. Sellers of electrical goods needed to supply the right ones for use there. My 200v coffee pot survived about 1 year on 240v elsewhere, my soldering iron - quite a bit longer. -- From KT24 Using a RISC OS computer running v5.18 |
Electricity: 3 phase query
On 07/07/2013 15:32, wrote:
I mean they're clearly two different disciples entirely. In my typically millivolt/milliamp world, we don't have to contend with forces sufficient to rip a machine's internals to pieces as you do with power engineering, so the need for nice, smooth 3 phase supplies simply doesn't arise in the first place! I found doing a bit of software development work on high power HF amplifiers / transmitters was quite enlightening in that respect... It certainly changes ones TTL/5V view of the world, when dealing with 10kV step up transformers! -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Electricity: 3 phase query
certainly up to 1962, Cambridge town was supplied wth 200v mains. Sellers of electrical goods needed to supply the right ones for use there. My 200v coffee pot survived about 1 year on 240v elsewhere, my soldering iron - quite a bit longer. Did we ever settle that Ac or DC argument Can't remember now;!)... -- Tony Sayer |
Electricity: 3 phase query
On 07/07/2013 14:43, The Other Mike wrote:
On Sun, 7 Jul 2013 05:59:03 -0700 (PDT), wrote: Hi gang, AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right? No good tapping into just one of the other live wires you need two more. Five wires in total L1 L2 L3 N E Plus a new three phase meter (or another two single phase ones) and a big hole in your bank account Not entirely sure, but when they replaced the main fuse and housing here some years ago, I'm sure I remember seeing four cores (three phases + neutral, with the sheath as earth). It could well be that they brought 3-phase to every house on the road when they were built in the 30s and only connected one phase at each. If I were to need 3-phase, that'd be a useful cost saving! SteveW |
Electricity: 3 phase query
In article , SteveW
wrote: On 07/07/2013 14:43, The Other Mike wrote: On Sun, 7 Jul 2013 05:59:03 -0700 (PDT), wrote: Hi gang, AIUI, out in the road there are three live wires and one neutral. The phases of the lives are 120 degrees out of phase with one another. The potential difference between any two live wires is 440V. The potential difference between any live and neutral is 230V. Domestic supplies only tap one live and the neutral to give you a single phase supply, so if you want a 3 phase supply for a workshop or whatever, you have to get the leccy blokes in to dig up the road and tap you into one of the other live wires. Do I have that right? No good tapping into just one of the other live wires you need two more. Five wires in total L1 L2 L3 N E Plus a new three phase meter (or another two single phase ones) and a big hole in your bank account Not entirely sure, but when they replaced the main fuse and housing here some years ago, I'm sure I remember seeing four cores (three phases + neutral, with the sheath as earth). It could well be that they brought 3-phase to every house on the road when they were built in the 30s and only connected one phase at each. If I were to need 3-phase, that'd be a useful cost saving! This house (built 1911) has all 3 phases incoming - I assume so proper balance could be obtained empirically. When they built a new estate of 25 bungalows, just round the corner, some 30 years ago - they were all on the same phase. How things change. -- From KT24 Using a RISC OS computer running v5.18 |
Electricity: 3 phase query
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Electricity: 3 phase query
On Sunday, July 7, 2013 9:17:11 PM UTC+1, charles wrote:
certainly up to 1962, Cambridge town was supplied wth 200v mains. There's still a bit of kit up at the Institute of Astronomy which runs at 200V. Apparently the electricity board threw up their hands in horror at the complexity of replacing it, and just fitted a suitable transformer. |
Electricity: 3 phase query
On 08/07/2013 06:14, charles wrote:
In article , SteveW wrote: .... Not entirely sure, but when they replaced the main fuse and housing here some years ago, I'm sure I remember seeing four cores (three phases + neutral, with the sheath as earth). It could well be that they brought 3-phase to every house on the road when they were built in the 30s and only connected one phase at each. If I were to need 3-phase, that'd be a useful cost saving! This house (built 1911) has all 3 phases incoming - I assume so proper balance could be obtained empirically. It was once normal practice to connect each house in turn to a different phase. As you say, that was to achieve phase balance. When they built a new estate of 25 bungalows, just round the corner, some 30 years ago - they were all on the same phase. How things change. That stops people importing 400v into their house by putting an extension lead over the fence, or otherwise sharing supplies. Colin Bignell |
Electricity: 3 phase query
On 08/07/2013 15:12, Nightjar wrote:
On 08/07/2013 06:14, charles wrote: In article , SteveW wrote: ... Not entirely sure, but when they replaced the main fuse and housing here some years ago, I'm sure I remember seeing four cores (three phases + neutral, with the sheath as earth). It could well be that they brought 3-phase to every house on the road when they were built in the 30s and only connected one phase at each. If I were to need 3-phase, that'd be a useful cost saving! This house (built 1911) has all 3 phases incoming - I assume so proper balance could be obtained empirically. It was once normal practice to connect each house in turn to a different phase. As you say, that was to achieve phase balance. When they built a new estate of 25 bungalows, just round the corner, some 30 years ago - they were all on the same phase. How things change. That stops people importing 400v into their house by putting an extension lead over the fence, or otherwise sharing supplies. Which if your road is wired like that, would be a pretty cheap way of getting three phase if you get on with both neighbours ;-) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Electricity: 3 phase query
On 08/07/2013 15:24, John Rumm wrote:
On 08/07/2013 15:12, Nightjar wrote: On 08/07/2013 06:14, charles wrote: In article , SteveW wrote: ... Not entirely sure, but when they replaced the main fuse and housing here some years ago, I'm sure I remember seeing four cores (three phases + neutral, with the sheath as earth). It could well be that they brought 3-phase to every house on the road when they were built in the 30s and only connected one phase at each. If I were to need 3-phase, that'd be a useful cost saving! This house (built 1911) has all 3 phases incoming - I assume so proper balance could be obtained empirically. It was once normal practice to connect each house in turn to a different phase. As you say, that was to achieve phase balance. When they built a new estate of 25 bungalows, just round the corner, some 30 years ago - they were all on the same phase. How things change. That stops people importing 400v into their house by putting an extension lead over the fence, or otherwise sharing supplies. Which if your road is wired like that, would be a pretty cheap way of getting three phase if you get on with both neighbours ;-) When I worked for an electricity board, it was more usually done surreptitiously, in one case by cutting small holes through the wall and driving six inch nails through the neighbour's meter tails, in order to keep the electricity bill down. Colin Bignell |
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