POLEpig

Discussion in 'General Electronics Chat' started by na5m, Jul 19, 2012.

  1. na5m

    Thread Starter New Member

    Jul 19, 2012
    14
    0
    To what does the other end of the primary side of a residential step-down transformer
    get connected to? Obviously, one end of the primary is connected
    to the high-voltage distribution line. The other end I don't really know
    where it goes

    [​IMG]
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    In a 3 wire distribution system the obvious connection for the primary of a single phase transformer would be between any two phases.
     
  3. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    Around here we have the 3 phases running on crossbars on the pole and a grounded neutral running below them. Each residential transformer drop is tied from a phase to this neutral.
     
    Last edited: Jul 19, 2012
  4. PackratKing

    Well-Known Member

    Jul 13, 2008
    850
    215
    I can't speak to 3-phase due to insufficient experience........

    In residential 240, where the bus bars are 180° apart regarding phase, providing either 120 or 240vac.

    As wired to normal household outlets, you would hook one transformer primary lead ---- Via a switch and fuse or circuit breaker to the hot [ black ] lead and the other lead to neutral, which in some places is also run to earth ground....

    If you have a transformer rated for 240, ----- Via a properly wired outlet and a plug intended for 240 applications, such as a clothes-dryer receptacle.
    You would connect one primary lead to each hot line, with your primary center-tap if present -- to neutral, or to earth ground.
    The item so powered demanding a switch, DPDT that will break both hot leads simultaneously, and fuse or circuit breaker on each leg.
     
    Last edited: Jul 20, 2012
  5. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
    At my house, the local transformer is fed from a kilovolt line and it must be using a neutral wire or an earth ground. I can tell because only one energized wire is approching and it has 2-disk insulators.
     
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
    1,153
    304
    I'll bet if you look around the pole you'll see a bare copper wire about a #6 stapled to the pole and going down into the ground.
     
  7. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
    There is a bare wire coming from another pole but I don't know if that is the ground because I'm too lazy to walk over there and look. Point is: some local transformers are not fed from 2 phases of a 3 phase supply.
     
  8. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    It may be a little difficult to follow, but here's a diagram showing how the entire system works:

    [​IMG]
     
    Sensacell, PackratKing and BSomer like this.
  9. na5m

    Thread Starter New Member

    Jul 19, 2012
    14
    0
    The conductor that I have dotted in red, where is it physically located?
    I can see the three high-voltage phase conductors up on the power pole, but
    it looks like this neutral conductor dives into the ground at the base of the power pole
    in my neighborhood.

    THANKS for all the replies!

    [​IMG]
     
  10. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
    That's because it IS ground.
    One of those dots is inside a transformer. The rest are called, "neutral" by electricians.
     
  11. na5m

    Thread Starter New Member

    Jul 19, 2012
    14
    0
    The conductor I have highlighted in red, can it be strung
    above ground on the pole, or, alternatively, laid underground?
    In the following picture, it seems that the power company
    has placed this conductor underground because there is a
    conductor running down the pole and disappearing into the
    earth.

    [​IMG]
    .
    [​IMG]
     
  12. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    As mentioned before, the conductor going down the pole and into the ground is just that--ground.
     
  13. na5m

    Thread Starter New Member

    Jul 19, 2012
    14
    0
  14. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    Looks about the same as in the diagram I posted :D

    So yes, I would say it is accurate.
     
  15. na5m

    Thread Starter New Member

    Jul 19, 2012
    14
    0
    So in post #11, the red line is actually terra firma earth, and not an actual wire?
     
  16. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
    No. The red line is a wire that is CONNECTED to terra firma.

    Are you having trouble with Ground = neutral = earth = terra firma?
     
    DerStrom8 likes this.
  17. DerStrom8

    Well-Known Member

    Feb 20, 2011
    2,428
    1,328
    As #12 said, the Red line is neutral, which is ground, which is connected to earth. It's all one and the same, in this scenario.
     
  18. na5m

    Thread Starter New Member

    Jul 19, 2012
    14
    0
    So from the ground (terra firma), how does the current get back to the generating station & complete its circuit? Does it behave like SWER?
    Like in my revised picture below?

    [​IMG]

    Thanks for all your helpful answers.
     
  19. #12

    Expert

    Nov 30, 2010
    16,247
    6,744
    The current travels on a grounded conductor called a wire to get back to the generating section. The local ground is just a safety ground, not a current carrying ground. The red wires you put in that last drawing forgot to include the current carrying neutral wire.
     
  20. na5m

    Thread Starter New Member

    Jul 19, 2012
    14
    0
    So you're saying that there is a neutral wire returning to the power generator, like in the below picture?

    [​IMG]