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.
correct or
incomers to
substantial
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
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
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.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:
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.
without any
100a x 230v (nominal) = 23kWBe 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 Lots of big motor with high starting current in my home workshop, as I explained to him.
AWEM
On Sun, 14 Jan 2007 14:19:48 GMT someone who may be "Julian" wrote this:-
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.
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
Persistent low voltages will also damage things like induction motors. The fridge freezer being the most likely victim.
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.
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.
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.
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.
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...
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 214vHave 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.
sorry, ROMS = RMS!
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.
incomers, you
welding
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
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.
Already stated thus:
09:00, measured at incomeres.ie connection from meter to bus on the fuse box.
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.
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