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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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Mains Voltage
Quick question for the electrical boffins:
AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Thanks Julian. |
#2
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Mains Voltage
"Julian" wrote in message ... Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Thanks Julian. My immediate reaction to your figures is that you have a high resistance in your feed to the property - no way should 6.5 Kw drop 34 volts or 13.6% AWEM |
#3
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Mains Voltage
In message , Andrew Mawson
writes "Julian" wrote in message ... Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Thanks Julian. My immediate reaction to your figures is that you have a high resistance in your feed to the property - no way should 6.5 Kw drop 34 volts or 13.6% Yeah -look for the molten pool of metal somewhere ... -- geoff |
#4
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Mains Voltage
"Julian" wrote in message ... Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Thanks Julian. This is apalling! 34 volts drop when you are drawing 26amps. So that is about a kW going to waste somewhere. At least if you are measuring this at the incomers, you are not paying for this lost power directly. It is just possible that off load you are measuring a falsely high value due to a non sinusoidal waveform and the way an avo treats that ( peak reading, RMS correction). Maybe repeat the measurements with a true RMS meter to check this. To answer your question, it does not matter too much what load the voltage is measured because it should not vary that much. Bob |
#5
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Mains Voltage
"Bob Minchin" wrote in message ... This is apalling! 34 volts drop when you are drawing 26amps. So that is about a kW going to waste somewhere. At least if you are measuring this at the incomers, you are not paying for this lost power directly. It is just possible that off load you are measuring a falsely high value due to a non sinusoidal waveform and the way an avo treats that ( peak reading, RMS correction). Maybe repeat the measurements with a true RMS meter to check this. Reply to all: OK, I borrowed my electrician friend's 'Fluke' meter and repeated the experiment, he thinks it's true ROMS but not certain. One thing is clear, it puts out some very different readings compared to my cheap Clarke thing - there's a lesson there in itself! 09:00, measured at incomeres (earth and neutral seem common - there is a word for this, but can't remember) no appreciable load (just PC and the odd light bulb) 236volts (all loads purely resistive) 5Kw 225v 9.5Kw 218v 12Kw 214v Have I got a case for complaint, or should I just keep quite? I'm aware that a new 'inverter' style high frequency welder will also solve my welding problems, this is the main issue, dimming lights aren't something I can get exited about. And I take the point that if the board adjust the tapings on their transformer then I may get other problems. Thanks Julian. |
#6
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Mains Voltage
"Julian" wrote in message ... sorry, ROMS = RMS! |
#7
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Mains Voltage
"Julian" wrote in message ... "Bob Minchin" wrote in message ... This is apalling! 34 volts drop when you are drawing 26amps. So that is about a kW going to waste somewhere. At least if you are measuring this at the incomers, you are not paying for this lost power directly. It is just possible that off load you are measuring a falsely high value due to a non sinusoidal waveform and the way an avo treats that ( peak reading, RMS correction). Maybe repeat the measurements with a true RMS meter to check this. Reply to all: OK, I borrowed my electrician friend's 'Fluke' meter and repeated the experiment, he thinks it's true ROMS but not certain. One thing is clear, it puts out some very different readings compared to my cheap Clarke thing - there's a lesson there in itself! 09:00, measured at incomeres (earth and neutral seem common - there is a word for this, but can't remember) no appreciable load (just PC and the odd light bulb) 236volts (all loads purely resistive) 5Kw 225v 9.5Kw 218v 12Kw 214v Have I got a case for complaint, or should I just keep quite? I'm aware that a new 'inverter' style high frequency welder will also solve my welding problems, this is the main issue, dimming lights aren't something I can get exited about. And I take the point that if the board adjust the tapings on their transformer then I may get other problems. Thanks Julian. As others have said, with this sort of fault you will have excessive light flickering, as will the other house you mention on the same transformer. It's probably worth seeing what effect your welder has on their lights, and maybe having a joint approach to the supplier. AWEM |
#8
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Mains Voltage
In article ,
Andrew Mawson wrote: As others have said, with this sort of fault you will have excessive light flickering, as will the other house you mention on the same transformer. It's probably worth seeing what effect your welder has on their lights, and maybe having a joint approach to the supplier. AFAIR, I thought that FiL made a mistake in using the words 'motor mechanic', 'welding', and 'flickering lights'. The electricity Co were not interested in replacing the transformer. I suppose an intermittant load, such as welding, would not generate enough revenue to cover the cost of installing an uprated transformer. The OP does have a case here though because the voltage is below 230 -6% with only a 12KW load. It would be useful for him to check the voltage when both houses are taking no load. Anywhere near 250V would be ammunition to argue *against* their simple getout of tapping up. -- Tony Williams. |
#9
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Mains Voltage
Tony Williams wrote:
In article , Andrew Mawson wrote: As others have said, with this sort of fault you will have excessive light flickering, as will the other house you mention on the same transformer. It's probably worth seeing what effect your welder has on their lights, and maybe having a joint approach to the supplier. AFAIR, I thought that FiL made a mistake in using the words 'motor mechanic', 'welding', and 'flickering lights'. The electricity Co were not interested in replacing the transformer. I suppose an intermittant load, such as welding, would not generate enough revenue to cover the cost of installing an uprated transformer. The OP does have a case here though because the voltage is below 230 -6% with only a 12KW load. It would be useful for him to check the voltage when both houses are taking no load. Anywhere near 250V would be ammunition to argue *against* their simple getout of tapping up. Those pole transformers don't have taps. I dunno if better ones are available..as I said. mostly they prefer to underground in the case of any serious faults wherever possible. Even 11KV overheads are not being built..too much maintenance in the gales. |
#10
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Mains Voltage
Julian wrote:
5Kw 225v 9.5Kw 218v 12Kw 214v Have I got a case for complaint, Where are you measuring the voltage? To avoid including voltage drop in the house wiring you need to do it on the busbars of the consumer unit (preferably using fused test leads), or at a point on a different final circuit to the one you are loading. Also take several sets of readings and average the results. -- Andy |
#11
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Mains Voltage
"Andy Wade" wrote in message ... Where are you measuring the voltage? To avoid including voltage drop in the house wiring you need to do it on the busbars of the consumer unit (preferably using fused test leads), or at a point on a different final circuit to the one you are loading. Already stated thus: 09:00, measured at incomeres. ie connection from meter to bus on the fuse box. |
#12
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Mains Voltage
Julian wrote:
OK, I borrowed my electrician friend's 'Fluke' meter and repeated the experiment, he thinks it's true ROMS but not certain. One thing is clear, it puts out some very different readings compared to my cheap Clarke thing - there's a lesson there in itself! Possibly, however you can't rely on getting the same readings each day since it is not only your property providing the load. The true RMS nature of the meter may have had an impact if you have a reasonable amount of load that is not at a unity power factor. 09:00, measured at incomeres (earth and neutral seem common - there is a word for this, but can't remember) TN-C-S and PME usually. no appreciable load (just PC and the odd light bulb) 236volts (all loads purely resistive) 5Kw 225v 9.5Kw 218v 12Kw 214v The situation was probably worse than your figures initially suggest since I guess you were assessing the load by reading the power consumption off the spec plate on the equipment. Since you were not actually feeding the specified voltage, the actual power drawn by the resistive load will have been below spec. So 214V at 11kW is probably more likely. If you have access to a clamp meter that you could stick round one of the meter tails then that would give you much more accurate information regarding the actual current load. Have I got a case for complaint, or should I just keep quite? I'm aware that Yes you do have a case for complaint. There is no need to mention the welding requirement as such, but just commenting on dim lights, and other electrical goods not functioning as they should - especially early evening etc ought to be enough. (A friend had a similar problem in that his garage door opener would not work in the evening when the supply fell to 200V. Another friend recently got compensation for a new freezer after a couple of days of persistently low volts at his premises pushed it over the edge (although that was down to 100V on occasion)) a new 'inverter' style high frequency welder will also solve my welding problems, this is the main issue, dimming lights aren't something I can get exited about. And I take the point that if the board adjust the tapings on their transformer then I may get other problems. You would need to point out the big swing in voltage - there is a good chance you could be close to the upper limit with no load (including the neighbours). -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#13
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Mains Voltage
"John Rumm" wrote in message ... Julian wrote: OK, I borrowed my electrician friend's 'Fluke' meter and repeated the experiment, he thinks it's true ROMS but not certain. One thing is clear, it puts out some very different readings compared to my cheap Clarke thing - there's a lesson there in itself! Possibly, however you can't rely on getting the same readings each day since it is not only your property providing the load. Yes, I understand that, but I had the two meters running together for comparison. The true RMS nature of the meter may have had an impact if you have a reasonable amount of load that is not at a unity power factor. 09:00, measured at incomeres (earth and neutral seem common - there is a word for this, but can't remember) TN-C-S and PME usually. no appreciable load (just PC and the odd light bulb) 236volts (all loads purely resistive) 5Kw 225v 9.5Kw 218v 12Kw 214v The situation was probably worse than your figures initially suggest since I guess you were assessing the load by reading the power consumption off the spec plate on the equipment. Since you were not actually feeding the specified voltage, the actual power drawn by the resistive load will have been below spec. So 214V at 11kW is probably more likely. That's true, I never thought of that. Yes I just looked at the rating labels (fan heaters and kettles) If you have access to a clamp meter that you could stick round one of the meter tails then that would give you much more accurate information regarding the actual current load. My mate's got one of those, I'll borrow it soonest. Have I got a case for complaint, or should I just keep quite? I'm aware that Yes you do have a case for complaint. There is no need to mention the welding requirement as such, but just commenting on dim lights, and other electrical goods not functioning as they should - especially early evening etc ought to be enough. I'm on the blower to them tomorrow. I've been chatting with my neighbours, and they have noticed dimming lights when I weld - so the problem is common to both our installations. Next door are nice people, they're not bothered by my welding because it is infrequent and we do favours for each other, and they are prepared to complain too to help my case. Julian. |
#14
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Mains Voltage
"Julian" wrote in message ... "John Rumm" wrote in message ... Julian wrote: OK, I borrowed my electrician friend's 'Fluke' meter and repeated the experiment, he thinks it's true ROMS but not certain. One thing is clear, it puts out some very different readings compared to my cheap Clarke thing - there's a lesson there in itself! Possibly, however you can't rely on getting the same readings each day since it is not only your property providing the load. Yes, I understand that, but I had the two meters running together for comparison. The true RMS nature of the meter may have had an impact if you have a reasonable amount of load that is not at a unity power factor. 09:00, measured at incomeres (earth and neutral seem common - there is a word for this, but can't remember) TN-C-S and PME usually. no appreciable load (just PC and the odd light bulb) 236volts (all loads purely resistive) 5Kw 225v 9.5Kw 218v 12Kw 214v The situation was probably worse than your figures initially suggest since I guess you were assessing the load by reading the power consumption off the spec plate on the equipment. Since you were not actually feeding the specified voltage, the actual power drawn by the resistive load will have been below spec. So 214V at 11kW is probably more likely. That's true, I never thought of that. Yes I just looked at the rating labels (fan heaters and kettles) If you have access to a clamp meter that you could stick round one of the meter tails then that would give you much more accurate information regarding the actual current load. My mate's got one of those, I'll borrow it soonest. Have I got a case for complaint, or should I just keep quite? I'm aware that Yes you do have a case for complaint. There is no need to mention the welding requirement as such, but just commenting on dim lights, and other electrical goods not functioning as they should - especially early evening etc ought to be enough. I'm on the blower to them tomorrow. I've been chatting with my neighbours, and they have noticed dimming lights when I weld - so the problem is common to both our installations. Next door are nice people, they're not bothered by my welding because it is infrequent and we do favours for each other, and they are prepared to complain too to help my case. Julian. So you need to talk in terms of lights flickering as the 'fridge starts up and when you put the kettle on, and going really dim with the electric cooker, and your electronic alarm clock keeps resetting and you're worried if perhaps there is a safety issue - and perhaps sound a little panicky G (and should all that snow have melted SO quickly arround their transformer last winter) AWEM |
#15
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Mains Voltage
Julian wrote:
Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? That is the specification. In reality much of the UK supply is still at 240V like it always was since that meets the above spec. My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Are you out in the sticks with a long overhead supply? It sounds as if your supply has a rather higher than desireable impedance. If you have a 60A supply and are dropping 34V on a load of only 27A that would suggest you are going to be down to 175V on full load, which is way too low, and likely to cause problems. I think I would be tempted to contact the supplier about that. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#16
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Mains Voltage
"John Rumm" wrote in message ... Julian wrote: Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? That is the specification. In reality much of the UK supply is still at 240V like it always was since that meets the above spec. My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Are you out in the sticks with a long overhead supply? It sounds as if your supply has a rather higher than desireable impedance. If you have a 60A supply and are dropping 34V on a load of only 27A that would suggest you are going to be down to 175V on full load, which is way too low, and likely to cause problems. I think I would be tempted to contact the supplier about that. Thanks to all the replies. You've made me more sure now that I do have a problem because I'm having difficulty welding with large rods, in my old house with the same equipment it was fine. Regarding my supply, I have a transformer up the top of a pole in my garden, this is a small jobby and supplies my next door neighbour too, but that's all it does. Here it is: http://freespace.virgin.net/julian.s...ransformer.JPG The other wires are telephone. There's a lot of very old looking wires up there, I guess some connections may have gone high resistance? Regarding a true RMS meter, I don't have such an animal, but I'll see if I can borrow one. My meter is a cheap Clarke thing. I'm going to repeat my tests, just to make sure of myself and then contact the supplier. What is full rated load, I note that I have a 100amp supplier fuse? Thanks again. Julian. |
#17
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Mains Voltage
"Julian" wrote in message ... "John Rumm" wrote in message ... Julian wrote: Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? That is the specification. In reality much of the UK supply is still at 240V like it always was since that meets the above spec. My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Are you out in the sticks with a long overhead supply? It sounds as if your supply has a rather higher than desireable impedance. If you have a 60A supply and are dropping 34V on a load of only 27A that would suggest you are going to be down to 175V on full load, which is way too low, and likely to cause problems. I think I would be tempted to contact the supplier about that. Thanks to all the replies. You've made me more sure now that I do have a problem because I'm having difficulty welding with large rods, in my old house with the same equipment it was fine. Regarding my supply, I have a transformer up the top of a pole in my garden, this is a small jobby and supplies my next door neighbour too, but that's all it does. Here it is: http://freespace.virgin.net/julian.s...ransformer.JPG The other wires are telephone. There's a lot of very old looking wires up there, I guess some connections may have gone high resistance? Regarding a true RMS meter, I don't have such an animal, but I'll see if I can borrow one. My meter is a cheap Clarke thing. I'm going to repeat my tests, just to make sure of myself and then contact the supplier. What is full rated load, I note that I have a 100amp supplier fuse? Thanks again. Julian. 100a x 230v (nominal) = 23kW Be aware when my company fuse blew the other month, although it was in a 100amp carrier, the fuse itself was only 60 amps. Chap from EDF was happy to put a 100amp in having drunk his tea G Lots of big motor with high starting current in my home workshop, as I explained to him. AWEM |
#18
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Mains Voltage
"Julian" wrote in message ... "John Rumm" wrote in message ... Julian wrote: Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? That is the specification. In reality much of the UK supply is still at 240V like it always was since that meets the above spec. My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Are you out in the sticks with a long overhead supply? It sounds as if your supply has a rather higher than desireable impedance. If you have a 60A supply and are dropping 34V on a load of only 27A that would suggest you are going to be down to 175V on full load, which is way too low, and likely to cause problems. I think I would be tempted to contact the supplier about that. Thanks to all the replies. You've made me more sure now that I do have a problem because I'm having difficulty welding with large rods, in my old house with the same equipment it was fine. Regarding my supply, I have a transformer up the top of a pole in my garden, this is a small jobby and supplies my next door neighbour too, but that's all it does. Here it is: http://freespace.virgin.net/julian.s...ransformer.JPG The other wires are telephone. There's a lot of very old looking wires up there, I guess some connections may have gone high resistance? Regarding a true RMS meter, I don't have such an animal, but I'll see if I can borrow one. My meter is a cheap Clarke thing. I'm going to repeat my tests, just to make sure of myself and then contact the supplier. What is full rated load, I note that I have a 100amp supplier fuse? Thanks again. Julian. I doubt if the problem is cable going high resitance as the power loss would soon escalate the problem. I suspect it is just an under rated transformer on the end of a long line. These sort of installations were fine in the days of light domestic loads and with equipment (and customers) that tolerated the voltage drop every now and then. Just not up to 21st century requirements. You might need to lay it on a Certainly a good plan to contact your local 'leccy board who will be responsible for the distribution - not necessarily your electricity supplier these days of course. You might need to lay it on a bit thick to get them motivated. One problem with these soggy supplies can be voltage spikes when loads are removed which can damage things like computers, VCRs etc Bob |
#19
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Mains Voltage
Bob Minchin wrote:
You might need to lay it on a bit thick to get them motivated. One problem with these soggy supplies can be voltage spikes when loads are removed which can damage things like computers, VCRs etc Persistent low voltages will also damage things like induction motors. The fridge freezer being the most likely victim. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#20
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Mains Voltage
Bob Minchin wrote:
"Julian" wrote in message ... "John Rumm" wrote in message ... Julian wrote: Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? That is the specification. In reality much of the UK supply is still at 240V like it always was since that meets the above spec. My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Are you out in the sticks with a long overhead supply? It sounds as if your supply has a rather higher than desireable impedance. If you have a 60A supply and are dropping 34V on a load of only 27A that would suggest you are going to be down to 175V on full load, which is way too low, and likely to cause problems. I think I would be tempted to contact the supplier about that. Thanks to all the replies. You've made me more sure now that I do have a problem because I'm having difficulty welding with large rods, in my old house with the same equipment it was fine. Regarding my supply, I have a transformer up the top of a pole in my garden, this is a small jobby and supplies my next door neighbour too, but that's all it does. Here it is: http://freespace.virgin.net/julian.s...ransformer.JPG The other wires are telephone. There's a lot of very old looking wires up there, I guess some connections may have gone high resistance? Regarding a true RMS meter, I don't have such an animal, but I'll see if I can borrow one. My meter is a cheap Clarke thing. I'm going to repeat my tests, just to make sure of myself and then contact the supplier. What is full rated load, I note that I have a 100amp supplier fuse? Thanks again. Julian. I doubt if the problem is cable going high resitance as the power loss would soon escalate the problem. I suspect it is just an under rated transformer on the end of a long line. Just the transformner, as when mine got replaced, all problems vanished. |
#21
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Mains Voltage
In article ,
"Julian" writes: Regarding my supply, I have a transformer up the top of a pole in my garden, this is a small jobby and supplies my next door neighbour too, but that's all it does. Here it is: http://freespace.virgin.net/julian.s...ransformer.JPG The other wires are telephone. There's a lot of very old looking wires up there, I guess some connections may have gone high resistance? That looks like rather a tiny transformer for two houses. More like the sort of thing which runs the light in a phone box out in the sticks. -- Andrew Gabriel |
#22
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Mains Voltage
Andrew Gabriel wrote:
That looks like rather a tiny transformer for two houses. More like the sort of thing which runs the light in a phone box out in the sticks. Yes, and old enough to date from the era when each house had one 60 W lamp and one 5 A socket in each room, perhaps... -- Andy |
#23
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Mains Voltage
In article ,
Julian wrote: Thanks to all the replies. You've made me more sure now that I do have a problem because I'm having difficulty welding with large rods, in my old house with the same equipment it was fine. Hmm... I'm glad I don't live next to anyone using a welder in a rural area. The flickerings were a source of constant irritation to FiL when a motor mechanic lived next door and my pal had several lightbulbs and his tv taken out during the dips/ /surges from his neighbour's welding. That became the source of bitter emnity, lasting for years and only solved when one of them died. ...... Here it is: http://freespace.virgin.net/julian.s...ransformer.JPG It doesn't look very large but the local electricity Co will probably be very reluctant to spend the money changing it. Watch out that they don't 'solve' the low voltage problem by tapping up the transformer. -- Tony Williams. |
#24
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Mains Voltage
On Mon, 15 Jan 2007 08:54:40 +0000 (GMT), Tony Williams wrote:
http://freespace.virgin.net/julian.s...ransformer.JPG It doesn't look very large but the local electricity Co will probably be very reluctant to spend the money changing it. Watch out that they don't 'solve' the low voltage problem by tapping up the transformer. Well the problem is regulation not low voltage, I wouldn't expect any competent power linesman to make that mistake. In my experience power distribution linesmen know their stuff, you don't F about with power distribution networks, get it wrong an there is a BIG BANG and lots of explaining or you or a collegue are pushing up the daisies. It does look a tad small but these trannys can deliver a surprising amount of juice. Ours is a square boxed jobbie a bit larger than that one but the cut out on the pole is 200A (46kW). One would assume that that cut out is designed to go pop before the tranny catches fire... I note that the 11kV feed is single phase, how long is this 11kV spur? But as others have pointed out that sort of volt drop at that load indicates 1kW or so going somewhere, a single joint dissipating that much power wouldn't last long. Report it to the local power company, they need to come and investigate. -- Cheers Dave. pam is missing e-mail |
#25
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Mains Voltage
Dave Liquorice wrote:
On Mon, 15 Jan 2007 08:54:40 +0000 (GMT), Tony Williams wrote: http://freespace.virgin.net/julian.s...ransformer.JPG It doesn't look very large but the local electricity Co will probably be very reluctant to spend the money changing it. Watch out that they don't 'solve' the low voltage problem by tapping up the transformer. Well the problem is regulation not low voltage, I wouldn't expect any competent power linesman to make that mistake. In my experience power distribution linesmen know their stuff, you don't F about with power distribution networks, get it wrong an there is a BIG BANG and lots of explaining or you or a collegue are pushing up the daisies. It does look a tad small but these trannys can deliver a surprising amount of juice. Ours is a square boxed jobbie a bit larger than that one but the cut out on the pole is 200A (46kW). One would assume that that cut out is designed to go pop before the tranny catches fire... Being able to deliver the juice with little drop, and being able to deliver it without going bang, are two different things. You cam easily dissipate 5KW or more from a pole mounted transformer without it going bang... Modern ones may be better, but the one that came off my pole was circa 1948 vintage and total utter crap at anything over a few amps. I know it wasn't the 11KV, because a new substation completely fixed it. And an 11KV line that sags because *one* person puts a few KVA on it is absolute balls. Its rated for ALL the people on it and maybe if they ALL switched on their tellies you might see a sag, but not just one sodding person. There is only one thing that fits the bill. The transformer, or connections to it. In short the problem is between the 11KV line and the consumer unit. Apart from bits of wire, there is only the pole mounted transformer, and my experience of those is that they are useless if more than 20 years old. In my case they were only to happy to get rid of it and have me bear part of the cost of a bit of undergrounding I suggest the OP uses this as a lever..to get the lot buried at little or no expense. I note that the 11kV feed is single phase, how long is this 11kV spur? More to the point how many other people are on it? If more than two it ain't the problem. Otherwise half a dozen people putting an electric fire on would dive it into the ground, at that implied impedance. But as others have pointed out that sort of volt drop at that load indicates 1kW or so going somewhere, a single joint dissipating that much power wouldn't last long. Report it to the local power company, they need to come and investigate. |
#26
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Mains Voltage
In article om, Dave
Liquorice writes On Mon, 15 Jan 2007 08:54:40 +0000 (GMT), Tony Williams wrote: http://freespace.virgin.net/julian.s...ransformer.JPG It doesn't look very large but the local electricity Co will probably be very reluctant to spend the money changing it. Watch out that they don't 'solve' the low voltage problem by tapping up the transformer. Well the problem is regulation not low voltage, I wouldn't expect any competent power linesman to make that mistake. In my experience power distribution linesmen know their stuff, you don't F about with power distribution networks, get it wrong an there is a BIG BANG and lots of explaining or you or a collegue are pushing up the daisies. It does look a tad small but these trannys can deliver a surprising amount of juice. Ours is a square boxed jobbie a bit larger than that one but the cut out on the pole is 200A (46kW). One would assume that that cut out is designed to go pop before the tranny catches fire... I note that the 11kV feed is single phase, how long is this 11kV spur? But as others have pointed out that sort of volt drop at that load indicates 1kW or so going somewhere, a single joint dissipating that much power wouldn't last long. Report it to the local power company, they need to come and investigate. Seen this problem out a a number of comms sites out in the sticks. Almost invariably an underrated transformer for today's loads. Grumble and kick up a fuss and get the tranny uprated!... -- Tony Sayer |
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Mains Voltage
Julian wrote:
"John Rumm" wrote in message ... Julian wrote: Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? That is the specification. In reality much of the UK supply is still at 240V like it always was since that meets the above spec. My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Are you out in the sticks with a long overhead supply? It sounds as if your supply has a rather higher than desireable impedance. If you have a 60A supply and are dropping 34V on a load of only 27A that would suggest you are going to be down to 175V on full load, which is way too low, and likely to cause problems. I think I would be tempted to contact the supplier about that. Thanks to all the replies. You've made me more sure now that I do have a problem because I'm having difficulty welding with large rods, in my old house with the same equipment it was fine. Regarding my supply, I have a transformer up the top of a pole in my garden, this is a small jobby and supplies my next door neighbour too, but that's all it does. Here it is: http://freespace.virgin.net/julian.s...ransformer.JPG The other wires are telephone. There's a lot of very old looking wires up there, I guess some connections may have gone high resistance? Regarding a true RMS meter, I don't have such an animal, but I'll see if I can borrow one. My meter is a cheap Clarke thing. I'm going to repeat my tests, just to make sure of myself and then contact the supplier. What is full rated load, I note that I have a 100amp supplier fuse? Thanks again. Julian. Those transformers were out up when at most a house would draw 3KW, and they are crap, old fashioned, use rubbish cores and you need a better one. With luck, they may underground your supply as well, if ou suggest it to them. |
#28
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Mains Voltage
On Sun, 14 Jan 2007 14:19:48 GMT someone who may be "Julian"
wrote this:- AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? [snip] So, under what load condition is the voltage measured? A nominal supply voltage of 230V does not mean that the supply will be at precisely 230V all the time. It means that it should be within the specified tolerances at all times, other than when there is a fault. The precise voltage at your terminals at any particular time will vary according to the load on the system (the load from you and other customers in the area) and what the automatic voltage regulation system is doing. It will be higher on no-load and will reduce as load is applied, because it is (partly) a function of the impedance of the external system. The same is true on your wiring. Your voltage regulation doesn't sound particularly good. How many km of 11kV route is there before it gets to the pole your photograph shows? It is certainly worth repeating these measurements and then having a gentle word with the technical people of your supplier, which may take persistence on your part. It may well be that a high resistance has developed somewhere on the external system. -- David Hansen, Edinburgh I will *always* explain revoked encryption keys, unless RIP prevents me http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54 |
#29
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Mains Voltage
"David Hansen" wrote in message ... On Sun, 14 Jan 2007 14:19:48 GMT someone who may be "Julian" wrote this:- AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? [snip] So, under what load condition is the voltage measured? A nominal supply voltage of 230V does not mean that the supply will be at precisely 230V all the time. It means that it should be within the specified tolerances at all times, other than when there is a fault. The precise voltage at your terminals at any particular time will vary according to the load on the system (the load from you and other customers in the area) and what the automatic voltage regulation system is doing. It will be higher on no-load and will reduce as load is applied, because it is (partly) a function of the impedance of the external system. The same is true on your wiring. Your voltage regulation doesn't sound particularly good. How many km of 11kV route is there before it gets to the pole your photograph shows? It is certainly worth repeating these measurements and then having a gentle word with the technical people of your supplier, which may take persistence on your part. It may well be that a high resistance has developed somewhere on the external system. It may be an idea to obtain a "Loop Tester" this device can be used to messure the effective resistance of the supply. The supply company or any electrican will be able to do this. Also measure the voltage between N and E when you have a high load. |
#30
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Mains Voltage
James Salisbury wrote:
It may be an idea to obtain a "Loop Tester" this device can be used to messure the effective resistance of the supply. The supply company or any electrican will be able to do this. Also measure the voltage between N and E when you have a high load. There's enough data in the original article to calculate the impedance: Voltage off-load = 250, on-load = 216, i.e. voltage drop = 34 V. The load is stated as 6.5 kW, but that's probably a rated value at 230 or 240 V. Assuming it's 240 (most equipment in use is still rated at 240 V) the load current at 216 V will be about 24.4 A. So the supply impedance = 34 / 24.4 = 1.4 ohm, which is awfully high. (This figure could include some of the internal house wiring, depending where the voltages were measured.) If the external impedance really is that high I would worry about the safety of the house wiring,particularly for any circuits of 30 A or more, where the fault clearance times could be rather long and normally-sized cables may not be adequately protected. -- Andy |
#31
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Mains Voltage
David Hansen wrote:
Your voltage regulation doesn't sound particularly good. How many km of 11kV route is there before it gets to the pole your photograph shows? It is certainly worth repeating these measurements and then having a gentle word with the technical people of your supplier, which may take persistence on your part. It may well be that a high resistance has developed somewhere on the external system. The 11KV will be OK. We are miles down one branch. Its fine. The transformer will not be. |
#32
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Mains Voltage
Julian wrote:
Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Thanks Julian. any load. You are due for a replacement street/house transformer. My old setup did this. The microwave caused every light to dim. Transformer on a pole. Yuk. When I finally undergrounded the supply I gort a huge steel cabinet in the garden corner. Problems solved., I have my own 100KVA substation :-) Contact the electricity company. They are supposed to be duty bound to fix this for you. |
#33
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Mains Voltage
On Sun, 14 Jan 2007 14:19:48 GMT, Julian wrote:
Quick question for the electrical boffins: AIUI mains voltage is now 230 volts -6% +10%. ie 216 to 253 - correct or rubbish? My question is how is it measured? I've stuck my AVO across the incomers to the main fuse box, and can get the voltage down to about 216v if I switch on about 6.5KWs of electrical load on the property - without any substantial load the voltage is nearer 250V. So, under what load condition is the voltage measured? Having read all through this thread, you've had an assortment of half-truths, some red herrings, and in one or two instances total rubbish. Your transformer looks as though it may be a 15kva rating. It's not a shape I immediately recognise, but from what you've said it seems like it's been there for quite a while. As someone else mentioned, it was typical of what was installed when most places had just a couple of lights and a plug. It doesn't look to have been cooked unduly, pole transformers can discolour quite badly if they're subjected to sustained overloads, and as an aside, the insulating oil inside the transformer turns quite acidic. The 11kv o/h line is very unlikely to be the problem, unless there's a dodgy joint somewhere. The industry went through a phase (if you'll pardon the pun) of using aluminium conductors for two or three decades. There can be - but may not actually be - a problem if there are poorly made bimetal joints out on the system. You also appear to have a two-wire lv system from the pole to the properties, probably splitting where it terminates on the building. Whatever readings you are getting, either using your own of your mate's Fluke meter are an indication, and only an indication. They are good enough to make your case that you have problems. I used to carry a laboratory sub-standard, regularly calibrated. That was the meter I'd believe. It could indicate a difference of several volts in the readings to other meters! You seem to have two quite separate problems, very poor regulation, due to an overloaded transformer and almost certainly caused by load growth with you and your neighbour. You are also using a welder, which is a dirty load, and may require a larger transformer than to meet a resistive load. You haven't mentioned anywhere about the rating of the welder, which is relevant. Firstly, you need to complain to your local distribution company that you and your neighbour are noticing significant dips on the lights, that, after all is how most people first become aware that they've got a problem. Make sure they realise you are both experiencing problems. Tell them that you've carried out some simple checks, and give them the voltages you've measured for different loads. Make sure they realise that you know the voltage shouldn't drop as much as it is for what is a normal load these days. If you think you're getting the run-around from a call centre monkey ask to speak to an engineer who deals with these types of complaints. They will almost certainly come and instal some sort of recording voltmeter as an initial move. This will give an indication of how the voltage varies with time of day. Whether or not you tell them about the welder is, of course, up to you. If you choose not to, don't be surprised if they carry out remedial works and you still find you've got problems. See my comments above! Freom your POV, I would also be looking to get separate cables installed from the transformer to each property. -- the dot wanderer at tesco dot net |
#34
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Mains Voltage
"The Wanderer" wrote in message ... Your transformer looks as though it may be a 15kva rating. It's not a shape I immediately recognise, but from what you've said it seems like it's been there for quite a while. It looks very old indeed. I would hazard a guess that it dates back to when mains electriciy first arrived in the sticks You also appear to have a two-wire lv system from the pole to the properties, probably splitting where it terminates on the building. The wire you see goes to the house next door (old farm house), The wire to our house (barn conversion) is buried underground and goes down the telegraph pole. You haven't mentioned anywhere about the rating of the welder, which is relevant. It just a DIY welder, it runs through a standard 13A plug, though at high settings it does tend to eat fuses - I've fixed that problem for good now! Firstly, you need to complain to your local distribution company that you and your neighbour are noticing significant dips on the lights, that, after all is how most people first become aware that they've got a problem. Make sure they realise you are both experiencing problems. Done, MANWEB couldn't have been more helpful, within a jiffy the girl started talking about safety (the world's gone safety barmy lately) and said it would be checked out very soon. I'll keep you posted. Julian. |
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