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Electrical Ground Question

  1. Aug 25, 2011 #1
    Earth acts as an electrical ground for the electrical supply that come to our home. But the ground, usually made of cement or stone is not a conductor like metal then how does it acts as an electrical ground.
     
  2. jcsd
  3. Aug 25, 2011 #2
    There is a "common" ground point somewhere outside house that goes to ground. Usually it is a thick wire without insulation on it. You can probably find yours if you look around your house, it is probably coupled with a pipe or something else so that it doesn't need its own hole coming out of the wall.
     
  4. Aug 25, 2011 #3
    Dear could you please make it more detailed. I am a student of science, so it will not be a problem if you make it a little technically detailed.
     
  5. Aug 25, 2011 #4

    dlgoff

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    http://en.wikipedia.org/wiki/Earth_ground" [Broken]

    This can be a serious problem for high voltage substations, power plants, or transmission lines. When there's a ground fault (say a transmission line down), the potential of the earth rises. This is called http://en.wikipedia.org/wiki/Earth_potential_rise" [Broken]. Depending on the soil conditions the fault can cause a potential difference between the feet of a person standing near an energized ground.
     
    Last edited by a moderator: May 5, 2017
  6. Aug 25, 2011 #5
    What do you understand an electrical ground to be?
     
  7. Aug 25, 2011 #6

    Problem:

    As you have stated, there is a desire to form a common ground in the electrical system of a building to the Earth. This common ground isn't inherent in the building design because as you pointed out most buildings sit on concrete which isn't a good conductor and therefore isolate the electrical system of the building from the Earth.


    Solution:

    Take a metal wire from the electical system of the building and run it outside of the building and into the Earth.


    This is how the Earth acts a common ground for the electrical supply that comes into your home even though the your home sits on cement and stone.


    I don't know how to state it any more technically, it is a very simple concept. It also sounds like you don't really understand how the common ground and electrical return work and differ.
     
  8. Aug 25, 2011 #7
    soil with minerals mix with water become quite a good conductor. Electricians get earth ground by pounding a 6' copper rod into the ground and use it as earth ground. Nobody said it is a perfect conductor nor you suppose to use it as signal or power return, it just establish a reference and provide safety.
     
  9. Aug 25, 2011 #8
    Something I found out the hard way when I was a teenager:

    Concrete conducts electricity pretty well.
     
  10. Aug 25, 2011 #9
    it is the moisture and minerals that conduct, not the concrete.
     
  11. Aug 26, 2011 #10
    Minerals?

    Care to expound on that a bit more?


    thanx!
     
  12. Aug 26, 2011 #11
    Ionized compounds that dissolves in water make the solution conductible. Like putting salt (NaCl) will make water conducting electricity. There are a lot of mineral salts that acts the same.

    Concrete is porous and it is like a sponge contacting the earth.
     
    Last edited: Aug 26, 2011
  13. Aug 26, 2011 #12

    jim hardy

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    "Ground" is widely misunderstood.

    Conceptually "ground" is just another wire in the circuit. The difficult part to grasp is that it goes everywhere.

    An electrical system will operate fine with no connection to "ground" just as it does in a flashlight or airplane.. The British call it "earth" which i prefer because that distinguishes it from 'circuit common'. In household electical systems 'circuit common' is tied solidly to 'earth' or 'ground' so that you, when touching an appliance, will not form the path of least resistance from circuit common to earth-ground.

    Simplify your thinking - there's a lot to be learned about 'grounding' just by contemplating the humble flashlight.

    Google "IEEE Green Book"

    old jim
     
  14. Aug 26, 2011 #13
    Hear Hear.

    The property which makes something a 'ground' is that it does not change its potential regardless of the current that flows in or out - within the limits of operation.
    There is no requirement for the ground to possess low resistance.

    In many instances the planet Earth can act as such a source or sink.

    https://www.physicsforums.com/showthread.php?t=382007&highlight=earth&page=2
     
    Last edited: Aug 26, 2011
  15. Aug 26, 2011 #14

    dlgoff

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    This isn't necessarily ture.
    http://en.wikipedia.org/wiki/Single-wire_earth_return" [Broken]
     
    Last edited by a moderator: May 5, 2017
  16. Aug 26, 2011 #15

    jim hardy

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    I have a neighbor who wired a barn that way, SWER. I told him it was a hazard.

    I was not aware it is used in some places for medium voltage distribution. I was aware of its use in HVDC transmission where there is sophisticated protective equipment to keep it safe.

    From same Wiki:
    ""Many national electrical regulations (notably the U.S.) require a metallic return line from the load to the generator.[12] In these jurisdictions, each SWER line must be approved by exception.""
    and ""SWER systems are designed to limit the voltage in the earth to 20 volts per meter to avoid shocking people and animals that might be in the area."
    I hope they age gracefully. I wouldn't get close to one of them.

    But as stated, ground is "just another wire" that goes everywhere.
    If an engineer decides to use it for one of his current carrying conductors in an area frequented by humans, well, it's on his conscience.


    old jim
     
  17. Aug 26, 2011 #16

    phinds

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    So you don't believe that electronics in flashlights and airplanes will always work unless they are connected to earth ground? I'm being sarcastic, of course, but I'd like an example of when you think it WOULD fail.
     
  18. Aug 26, 2011 #17

    dlgoff

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    By "fail", you mean an open earth?
     
  19. Aug 26, 2011 #18

    phinds

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    No, I mean FAIL, which is what you said it would do. The original statement was "An electrical system will operate fine with no connection to "ground" just as it does in a flashlight or airplane.

    Seems to me the opposite of "operate fine" is "fail".
     
  20. Aug 27, 2011 #19

    dlgoff

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    Where did I say FAIL. Sure flashlighs will work without a ground. What's the problem?
     
    Last edited by a moderator: May 5, 2017
  21. Aug 27, 2011 #20

    phinds

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    The original statement was "An electrical system will operate fine with no connection to "ground" just as it does in a flashlight or airplane." and you said that is not necessarily true.

    Seems to me the opposite of "operate fine" is "fail". THAT's what I was responding to. Don't see what's confusing about that.


    as for your statement:

    I absolutely agree but this has nothing to do with electronics (radio's, TVs, flashlights, etc), it's about power distribution.
     
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