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  1. DaveL
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    DaveL EF Member

    Location:
    Monforte de lemos
    Hello from Spain!

    I am after some help and advice.

    Whilst checking my supply ( which is TT and the whole installation is protected by a 30ma RCD) I have found the following

    With the earth connected to the rod
    L to N 240v
    L to E 345v
    N to E 148v

    If I disconnect the earth rod, at the consumer unit I get

    L to N 235
    L to E 214v
    N to E 7v

    I rigged up a testing bulb and the voltage is real and not a phantom from my meter. The bulb lights up. Brighter on the higher volts. If I try this after the RCD it trips ( phew! ) which I'm guessing means the system is normally balanced.

    When I checked at the incoming supply point, with my Consumer unit isolated, I earthed to the metal leg that holds my supply box I get the same voltages of 345v and 148v.

    We live in a very remote rural location.

    Is it possible to have both the N and L energised?

    Thank you

    Dave
     
  2. marconi
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    marconi Regular EF Member

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  3. Murdoch
    Online

    Murdoch Electrician's Arms

    Location:
    Woking
    Wonder what the OP is using to get the voltage readings ....?
     
  4. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    slightly off topic, but i had an unusual voltage found yesterday. as part of a few other jobs, one was to replace a broken lamp holder on a pendant. ceramic rose, 60 years of paint crud over it, twisted cotton covered flex to holder. first quick check was with voltstick to see if it was switched on or not. either position of switch lit up the stick. so... carefully removing the terminal cover from the lamp holder, approved voltage tester (fluke) reads 230V with switch on. 24V with switch off. suspecting it's just a phantom, but wonder why the stick lit. i know you can't trust them, but it's strange.
     
  5. KEV 1 N
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    KEV 1 N Regular EF Member

    Location:
    Durham
    I’ve had that happen with volt sticks, I think they sense voltage as little 10v, as once mine was lighting up at a light switch yet there was no mains to it, only a signal cable from the LCM unit
     
  6. DaveL
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    DaveL EF Member

    Location:
    Monforte de lemos
    Guys, voltage is taken using a digital volt meter. I know these can give false readings hence wiring up an incandescent bulb to check that it is real. It is...

    The RCD trips when testing from the protected side but illuminates The bulb from the unprotected side.
     
  7. Murdoch
    Online

    Murdoch Electrician's Arms

    Location:
    Woking
    Before you start damaging all your electrical appliances I think you need a local spark to confirm the supplier voltages .......................

    Are you single phase or multi phase?
     
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  8. DaveL
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    DaveL EF Member

    Location:
    Monforte de lemos
    In theory single phase.

    The voltage between L and N has always fluctuated. Any where from 230v to 245v. I've never checked the voltage to Earth before until a couple of days ago when I had an unexpected RCD trip. The weather has changed from dry and warm to wet and cold which I know can cause some issue with TT system. I've just checked the L to N voltages again with my back up inverter. It matches the same reading as my digital Meter. And is sitting at 238v. I've had no issue with the RCD since resetting other tripping it with the tester bulb when going from N or L to E.

    I'll get a local guy in to check the supply, but just want to know if there is a system where both L and N are energised to give a stable voltage between the 2?

    The infrastructure here is donkeys years old, wondering if this is a result of an upgrade from the old 120v system?
     
  9. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    If you have a fluctuating incoming voltage, this can trip your RCD
     
  10. static zap
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    static zap Regular EF Member

    Location:
    west midlands
    Does sound a bit 3 phase . (Local transformer- issue -lost earth )
    But a local spark will know whats normal for your DNO equivalent !
     
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  11. dmxtothemax
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    dmxtothemax Regular EF Member

    Location:
    Australia
    Business Name:
    David Haddock Electronic Repairs
    Clearly your earth line is NOT at earth potential !
    You have currents in your earth lines,
    Someone somewhere has a bad/poor neutral,
    And your earth line is providing a partial return path for them.
    it doesn't always have to be you,
    sometimes it can be your neighbour.
    Try isolating circuits and see if that voltage on the earth
    goes down or away.
     
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  12. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Hi - if I've understood correctly, it sounds like on the supply side their N is not connected to the General Mass of the Earth. If so, its likely a fault and needs looking at.
    IMG_0934.GIF IMG_0935.GIF
     
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    Last edited: Dec 6, 2017
  13. Sparkingmad
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    Sparkingmad Regular EF Member

    Location:
    Dorset
    I would agree it needs checking ASAP. I don’t know what the energy supplier network is like in Spain but if you were to contact them first and give them the readings you have they should come out and test it at your property first then at various points back to their transformer. If the fault is on their side and not on yours which it definitely sounds is the case there shouldn’t be a charge to you. Also ask them what the fault was and get them to write down the Ze next to your meter. I have seen it too many times where they come out and you never know if they have
    A) found anything
    B) rectified it
    So when you phone up they can never answer you. This is especially useful when you carry out an EICR and find Ze reading is borderline or over and you have a circuit where the Zs is too close to maximum value allowed under working conditions. So you have to go back out to recheck for yourself. Customers usually don’t like this as they get charged again for it.
     
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  14. marconi
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    marconi Regular EF Member

    My interpretation of the readings:

    With the earth connected to the rod
    L to N 240v
    L to E 345v
    N to E 148v

    and some on-line research which says TT is generally used in rural Spain, and areas which were once 3 phase 120V have been upgraded to 3 wire 220/240V distribution system

    is that your property has a 220/240 supply derived from a connection across 2 phases. Neither supply phase is earthed. Whether the secondary of the distribution transformer is star or delta I do not know but I would assume star so that the star point can be earthed. (There are ways of providing a star point for a delta winding using an earthing transformer see: Grounding transformer - Wikipedia - https://en.wikipedia.org/wiki/Grounding_transformer).

    The local potential of the earth rod with respect to the transformer ground/earth depends on all the earth leakage currents from each phase. See Millman's theorem: http://www.tandfonline.com/doi/pdf/10.1080/20464177.2003.11020168

    If all these leakage currents were absolutely equal then there would be no potential difference between local and transformer earths - which is impossible. If there is more leakage current from one phase than the others the local earth potential will be closer to that phase's potential.

    The readings to me indicate to me:

    1. the supply voltage is 240V.
    2. neither phase is earthed.
    3. the local star point is closer to the 'N' live conductor than the 'L' live conductor.
    4. the installation does not have a Neutral conductor it has two line conductors. Thus the use of N is wrong.
    5. If I am correct all switching will/must be double pole.

    This is my interpretation only - you need a Spanish sparks to check your installation is correct and that there are no external faults in the distribution circuit to your home.



     
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  15. DaveL
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    DaveL EF Member

    Location:
    Monforte de lemos
    Thank you for your responses. I've had a chat with one of my neighbours, sometime in the past everything in the area was 3 phase and has been converted to 1. The actual date wandered around a bit as we discussed the issue so not too sure how reliable the info is. I've found a friendly electrician who when I explained the issue nodded sagely and will be coming out to have a look at the weekend.

    The network here in Galicia is good in the towns but patchy in the sticks where we are. Our little hub is right on the end of the line and there are abandoned and collapsed barns and houses around. It was common practice here to splice into the mains and give yourself electricity in the barns and sometimes the houses for free. Where these have fallen into ruin and there is no record of an installation I guess it is very possible that the problem could stem from there.

    I'm surprised that nothing was picked up when they installed the new smart later but then again I suppose the problem could have manifested after the install.

    Anyway, I'll have a clearer understanding after the weekend. Thank you for you replies.
     
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  16. DaveL
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    DaveL EF Member

    Location:
    Monforte de lemos
    Hello Marconi,

    I've just seen your response as I was typing my note above. The new(ish) specs now state that only double pole RCDs and MCBs are to be used. In fact in my local building merchants they now only stock/sell double pole items.

    Now I now what to look for a little digging on the internet appears to confirm you theory of a 2 phase supply. Sorry, my nomenclature is probably wrong but I understand what you are saying regarding both Lines being energised.

    I'll post an update on Monday if anyone is interested.
     
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  17. Lucien Nunes
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    Lucien Nunes Mercury Arc Rectifier Trusted Advisor

    Location:
    London
    It does not matter whether it is supposed to be regular single-phase with earthed neutral, two lines from 3-phase delta, 2-phase or whatnot... No circuit conductor of a 230V supply should be 345V from earth. If those readings are correct, either what you think is earth isn't, or there's something badly wrong at the supply end! Get it checked en seguida!

    The fact that the voltages are all under 230 when you disconnect the rod, but the L-E is near the line voltage of a 3-phase system when it is connected, suggests the rather worrying scenario that the star point of the transformer has lost its earth, and one line (not the one feeding you) is leaking heavily to, or shorted to earth. This will be affecting all other consumers on your line and the other unfaulted line similarly, while the ones on the faulted line will be seeing what looks like a polarity reversal.
     
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    Last edited: Dec 6, 2017
  18. Percyprod
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    Percyprod Regular EF Member

    Location:
    Cumbria
    Definitely sounds like neutral fault on supply side and if a 3 phase this often happens. 3 phase in street, not necessarily to the property.
     
  19. marconi
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    marconi Regular EF Member

    LN wrote: ...suggests the rather worrying scenario that the star point of the transformer has lost its earth, and one line (not the one feeding you) is leaking heavily to, or shorted to earth.

    I wonder if you think these small changes are allowable:

    ....suggests the rather worrying scenario that:

    a. the star point of the transformer has lost or has a weak earth;
    or
    b. one line (not the one feeding you) is leaking heavily to, or shorted to earth;
    or
    c. in another installation fed by the transformer one line has been deliberately/erroneously connected to earth to create an earthed neutral.
     
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  20. Lucien Nunes
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    Lucien Nunes Mercury Arc Rectifier Trusted Advisor

    Location:
    London
    We can reasonably assume that the neutral conductor is properly continuous to the star point as the L-N voltage is correct and the OP doesn't mention connected equipment malfunctioning as would happen if the L-N voltage varied widely. We can probably also assume that it is 3-phase at the substation, rather than split-phase, since on a split-phase system with a lost earth reference the L-E voltage would be the algebraic sum of the L-N and N-E. Since this is not the case here, it is likely that the source of the voltage between N (approx same as star point) and mass of earth is out of phase with that of the OP's line, hence probably unusually high leakage from another line. Therefore the highest voltage anywhere on the secondary must be 415V, of which 345V appear to be between the zero wire (that should be neutral) and mass of earth.

    Unfortunately here our data runs out. We don't know the phase angle between the L-N and N-E voltages, so we can't use triangulation to calculate the relative magnitudes of the zero sequence leakage (which tends to hold the star point near earth due to symmetry) and the leakage that is causing the abnormal voltage. Therefore we can't calculate the relative impedances of the faulty N-E connection and the leakage. Academic anyway, as it's someone else's job to fix!
     
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  21. marconi
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    marconi Regular EF Member

    In my interpretation (#14) I have assumed a 3 wire 3 phase system without a neutral - 3 lines used for distribution, 240V between lines. Also poor ground conditions for the flow of earth currents hence my use of the term 'local star point' and the implied consequence of relatively high impedance between local and transformer earths.

    I could well be wrong - but it came from a comment in an IET forum on how the 120V was upgraded to 240V in rural areas. ( see mdhamish at IET Forums - Wiring in Spain - http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=6282)

    I could not find much information on Spain's LV network other than Schneider saying Spain has 400V using 3 and 4 wire distribution.

    Perhaps the OP can look out the window and tell us how many conductors he sees on any poles carrying the current to homes?

    As you say - enough speculation. :)
     
  22. DaveL
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    DaveL EF Member

    Location:
    Monforte de lemos
    I will certainly have a good look tomorrow.
     
  23. Lucien Nunes
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    Lucien Nunes Mercury Arc Rectifier Trusted Advisor

    Location:
    London
    The problem with that assumption is that, on a 3-phase delta system, there shouldn't be anything as high as 345V present anywhere, even with any combination of faults (barring freaky scenarios such as both a lost reference and someone having a large step-up autotransformer with a fault on the output pushing the whole distribution system off centre). The highest voltage that can be expected to appear with a combination of faults would be if the two lines other than the OP's line were leaking with equal impedance to E, and his line was not leaking at all. That would put the E midway along the vector between those two lines, creating an L-E voltage of *not what I just said, hang on..* f the readings are correct, I maintain that by far the most likely configuration is a 240/415V 3-phase 4-wire system.
     
  24. marconi
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    marconi Regular EF Member

    As you point I have made a blunder. One would need a 4 wire star system 240/415V and not a 4 wire star 140/240V nor 3 wire delta 240V to obtain 345V L-E.

    :)
     
  25. Lucien Nunes
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    Lucien Nunes Mercury Arc Rectifier Trusted Advisor

    Location:
    London
    And I too made the error of adding the phasors, expecting a voltage between 240 & 415, out of sheer force of habit, which I got. Of course the voltage in that situation would be sqrt((240)²-(240/2)²)=207V.
     
  26. DaveL
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    DaveL EF Member

    Location:
    Monforte de lemos
    Apologies just for confirmation. All I saw was " the readings are correct".

    Assuming my feed is 2 conductors from the 4 wires is that the case?

    I'll go into my field tomorrow as the supply line passes through it and see if I an tell how many conductors there are.

    I won't be cancelling the electrician either way as I want him to confirm everything is OK from my side before I call FENOSA.

    I would like to have an understanding of what system I may have so I can prepare the Spanish words and understand what he tells me with regards to the supply.

    Thank you
     
  27. marconi
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    marconi Regular EF Member

    Good. You need a Spanish electrician to attend.
     
  28. pirate
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    pirate Active EF Member

    Location:
    Glasgow
    Potencia, retorno, tierra...
    all you need to know. My experience of Spanish electricians is all good. OK, some existing (and some new) installations are just carp, but I have found that bringing an electrician in is just such good value and well worth it. They are well used to the old junk, and quite clued in to the newer ways...indeed, my CU has had to be updated twice in the last 10 years...I'm just waiting for Endesa to tell me I need a metal one! And don't forget, they do a good job at €17/hour...
    I first-fix at 12...includes a pie and a beer at 9am on a 20 minute break for breakfast...in the sun! Perfect!
     
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