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Volt drop at the intake - Just looking to compare with sunny Thailand.

crossy
A nice easy one.


On a "standard" UK domestic supply what sort of volt drop would you expect at the intake for a load of 50A?


In an urban environment and in a rural environment.


We are dropping about 30V (from a nominal 220V) at 50A, of course the other loads in the village may already have pulled things down to 205V!!

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    Dropping 30 volts at 50Amps sounds a bit much to me here in I get a drop of about 7 volts with around 40 amps load thats from a nominal 240 volts sometimes its a lot less as you say depends on other loads on your phase
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    Not even that at home here (SSE area 1960s PILC SNE service ) - about 5v step for a 40A shower. Hovers 245-240 ish depending on time of day. Tx is 150-180 metres away.

    That said I have seen 200V at a rural location where I used to live that was mid Hamshire, but cannot recall the current figures - that certainly dimmed when you put the kettle on, let alone an electric shower -  so it varies quite a bit even in the same DNO area.

    M.
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    The UK voltage is nominally 230V, although in reality it is often closer to 245V. At the meter terminals, the supply limits are 216.2V at the lower end, up to 253V. 


    Regards,


    Alan.
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    Standards overseas tend to differ.

    On a nominal 220 volt supply I would in most cases expect no more than 10% voltage drop at the intake, so about 198 volts minimum, plus a few percent within the consumers installation, so perhaps a minimum of about 190 volts at the appliance.


    Voltage regulators are readily available in countries where the voltage varies a lot. Some are automatic, others rely on manual adjustment.

    The better sorts are continually variable, the more basic style use simple step control. Often something like minus 6%, plus 6%, plus 12% and plus 18%.


    If your line voltage is regularly low, then a simple home made voltage booster is a possibility. A simple "plus 10%" transformer will often help a lot.
  • 0
    On a "standard" UK domestic supply what sort of volt drop would you expect at the intake for a load of 50A?

    Given that the L-N impedance is usually < 0.35Ω (the Ze limit for PME supplies is normally 0.35Ω, and of course N and PE are the same in that case), Ohms Law says it should be less than 17.5V - often less in practice. Of course that doesn't take into account the loads in neighbouring installations...

       - Andy.
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    I am not sure that this is an answerable question save for "not a lot".


    I think that diversity probably takes care of it, at least with UK infrastructure. However, if you have a relatively modest generator somewhere, and a village is at the end of a long distribution line (I was going to say network) then there must come a time when the generation cannot keep up.


    Just my thoughts!
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    AJJewsbury:
    On a "standard" UK domestic supply what sort of volt drop would you expect at the intake for a load of 50A?

    Given that the L-N impedance is usually < 0.35Ω (the Ze limit for PME supplies is normally 0.35Ω, and of course N and PE are the same in that case), Ohms Law says it should be less than 17.5V - often less in practice. Of course that doesn't take into account the loads in neighbouring installations...

       - Andy.


    Not just PME supply's very recently a few weeks 8 weeks to be precise had to have the DNO out to re attach the main earth to the cable sheath as part of the process the engineer did an earth loop test which showed an impedance of 0.238 ohms   don't know if 5his is a typical reading for a domestic intake whatever there would be a lot of amps in a short circuit fault. Let's hope that never happens


  • Former Community Member
    0 Former Community Member
    On a "standard" UK domestic supply what sort of volt drop would you expect at the intake for a load of 50A?


    Best ask our resident pro EV member as these things won't happen!!!!


    Regards


    BOD
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    the engineer did an earth loop test which showed an impedance of 0.238 ohms don't know if 5his is a typical reading for a domestic intake whatever there would be a lot of amps in a short circuit fault. Let's hope that never happens

    Sounds reasonable to me. Mine was about 0.15 last time I measured it - I'd guess anything between 0.1 and 0.3 would be fairly common.


    In theory the fault current could be a lot higher - the DNOs say it can be anything up to 16,000A for a single phase supply! (Hence UK CUs having a (conditional) 16kA rating).


       - Andy.
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    Thanks everyone, those are the sort of numbers I was expecting, it's not something I ever measured "back home".


    We have an AVR (automatic voltage regulator) which keeps the important stuff at steady 220V if the supply is above about 160V (basically a motorised variac).


    I went to look at a mate's new place a couple of weeks back, he was down to 150V at 5A!! (luckily they live very simply) Drop at the meter was insignificant, but at the other end of the 800m "tails"... Turns out whoever had run the cable had used a motley mix of assorted aluminium and copper as small as 6mm2 with a multitude of taped joints. He's got a couple of km of 95mm2 aluminium on the way (copper is just $$$ and has a nasty habit of wandering off in the night).

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