AC supply voltage variation

Discussion in 'Power Electronics' started by jaco_boon, Jun 23, 2016.

  1. jaco_boon

    Thread Starter New Member

    Jun 22, 2016
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    What could cause a drastic variation in voltage on a municipal supply to a house?
    Is it possible that something on the house circuit side of thee main switch is causing it? Or can it only be something on the supply side?
     
  2. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    The described difficulty may owe to any of several conditions - prominent among them being:

    1) Defective watt-hour meter/socket contacts.
    2) Problems with the primary fuse, distribution transformer proper, or service drop line (similar considerations apply to secondary network systems).
    3) Feeder or system-wide 'brown-out' conditions.

    The good news is that all of the above are the 'POCO's responsibility:D -- Though it may behoove you to identify the fault prior to reporting difficulty (inasmuch as most utilities bill for 'unfounded' service calls...)

    Assuming proper load-center OCP installation and absence of conspicuous arcing at or inbound of said load center - No!:)

    Best regards and good luck!
    HP:)
     
    Last edited: Jun 23, 2016
  3. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    Addendum:

    Re: 120V--N--120V service - an open neutral may produce the described symptoms Re: the 120V circuits --- Said circuits being thence 'stacked' in a 'series-parallel' arrangement line to line - permitting an EMF range at any 120V receptacle of (essentially) 0V-240V (dependent upon load distribution)...

    Best regards
    HP
     
    Last edited: Jun 23, 2016
  4. jaco_boon

    Thread Starter New Member

    Jun 22, 2016
    15
    2
    Tnx!
    Its an intermittent problem so I will have to wait for it to happen again and maybe make a video of my testing procedure and readings as proof before I can call out the municipality, because if they pitch up there and test to find nothing wrong (as at this moment) they'll probably think I'm "nuts" like some of the guys on this forum.( I spent some time discussing the problem on the forum last night while it was happening, sharing readings as I measured them and got the feeling that the very helpful members comments suggested that its not really possible).
    Thanks for your input, appreciate it!
     
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  5. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    A good start would be to check the integrity of your neutral connection via observation of the 'cross-line' EMF (i.e. any 240V circuit) during an 'event' -- Stability of the 240V supply under said conditions implicates the neutral connection -- Be warned that a 'bad' neutral may damage 120V loads via an 'over-voltage' condition!

    Best regards and, again, good luck!
    HP:)
     
  6. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Ground rods that connect to neutral at your breaker box do NOT last forever.
    It is a bare copper to copper connection between rod and wire using only a compression collar.

    Drive a new rod and make a new connection on clean copper.
    Also know that very dry ground, such as you would experience during drought can cause a high resistance neutral conductor condition, and cause voltage fluctuations based on current draw.
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    define "drastic"?
    State where/how you are determining there is a problem? Where are you measuring? What tool are you using?

    If you are measuring at an outlet in the room then the problem could be anywhere upstream.. And up to an including the distribution box is your issue.. Before that would be the utilities problem and sometimes they will throw a logger on and check it over a period of time..
     
  8. jaco_boon

    Thread Starter New Member

    Jun 22, 2016
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    Hi!
    Did all measurements at the point of supply entry on the main switch in the db box with a fluke T150 voltage tester
     
  9. jaco_boon

    Thread Starter New Member

    Jun 22, 2016
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    Voltage readings at this point of entry ranged between 0volts and 102 V (it is supposed to be, and is at the moment 230V
     
  10. Aleph(0)

    Member

    Mar 14, 2015
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    In usa ground and neutral aren't same thing cuz neutral is just center tap from transformer which is tied to ground and house wiring both so you still have neutral if you lose ground:cool:.
     
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  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Is your incoming supply via underground cabling or overhead cables? If overhead, can the cables at any point be touched by tree branches (which can cause intermittent shorting of line to neutral, or leakage from line to ground)?
     
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  12. Aleph(0)

    Member

    Mar 14, 2015
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    If you checked it before main house breakers its utilities trouble and you should call right now cuz is probably arcing which is major fire hazard!
     
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  13. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    yep.. call them immediately.. If your readings are correct then its already arcing and a fire/total loss of electricity is soon to follow..
    But its their problem not yours..
     
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  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I have yet to see the country of origin, although the problem could apply universally the distribution/measured voltage will be different according to country?o_O
    Max.
     
  15. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
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    FWIW I wish to add my voice to those of @Aleph(0) and @mcgyvr --- Don't await recurrence of the malfunction! - Please report your observations ASAP! Additionally, please be advised that transformer explosion is possible in the event of internal arcing! ('Praise' be to supplanting chlorinated dielectric compounds with combustible hydrocarbon substitutes:rolleyes::rolleyes::rolleyes:)

    Please take care!

    Best regards
    HP
     
    Last edited: Jun 23, 2016
  16. jaco_boon

    Thread Starter New Member

    Jun 22, 2016
    15
    2
    Thanks for al the input and advice, I really appreciate it.
     
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