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Thread: Ground rod in disturbed back-fill

  1. #21
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    Quote Originally Posted by kwired View Post
    I can recall many places where soil is sandy and you can nearly push a rod all the way in with bare hands.
    of course me me "drive it in with your bare hands" thus compliant

    here, as in so many areas, the resistance is normally so high one cant help but wonder if it s a lot of worry for nothing.
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  2. #22
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    Quote Originally Posted by augie47 View Post
    of course me me "drive it in with your bare hands" thus compliant

    here, as in so many areas, the resistance is normally so high one cant help but wonder if it s a lot of worry for nothing.
    i don't have any literature to back this up, but i believe(and know i could be wrong, i cannot find good published material on lightning related to this) ground electrode resistance is relative and should be viewed as relative to the location.

    what i mean by this is the less impedance a path has compared to the other options the current has the better. (you want lower impedance on the GEC compared to others, and relativity comes in here, the other paths are more resistive because of the "resistive" soil.)


    so 20 ohms in what we call "resistive soil" may be exactly as good as 5 ohms in what we consider "conductive" soil


    i believe most people visualize lightning somewhat as travelling along a conductor, while i visualize it similarly in a way but more of a emphasis on current flow of a battery. and relatively lower soil resistance changes the characteristics of the battery.

    again no good proof though, but if someone would point me to published literature telling me otherwise, i would appreciate it


    p.s. i know grounding electrode system is not a lightning protection system. this idea(pretty much pulled out of my a** theory) also applies to transient voltages although i know someone will say it doesn't.

  3. #23
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    <lecture>

    FWIW, I think the best way to think of a lightning strike is to consider a cloud or set of clouds as one plate of a capacitor and the earth as the other plate. A lightning strike is an internal dielectric breakdown of that capacitor.
    That accounts for the current flow without any external circuit or "return of current to it's source". It also explains the high frequency AC nature of the current (capacitance of the earth/clouds in series with the inductance of the path the lightning current follows.)
    The current flowing through the earth is simply the redistribution of charge across the larger area of the capacitor plate from a very localized dielectric breakdown.
    </lecture>

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  4. #24
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    Quote Originally Posted by GoldDigger View Post
    <lecture>

    FWIW, I think the best way to think of a lightning strike is to consider a cloud or set of clouds as one plate of a capacitor and the earth as the other plate. A lightning strike is an internal dielectric breakdown of that capacitor.
    That accounts for the current flow without any external circuit or "return of current to it's source". It also explains the high frequency AC nature of the current (capacitance of the earth/clouds in series with the inductance of the path the lightning current follows.)
    The current flowing through the earth is simply the redistribution of charge across the larger area of the capacitor plate from a very localized dielectric breakdown.
    </lecture>

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    i might agree with that, but i thought current didn't actually flow through capacitors though? you might not be saying it does. the dielectric breakdown is the part that makes me think you are though

    also i believe the more well versed people in lightning science call it a pulse current and not necessarily high frequency ac

  5. #25
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    Quote Originally Posted by Wire-Smith View Post
    i might agree with that, but i thought current didn't actually flow through capacitors though? you might not be saying it does. the dielectric breakdown is the part that makes me think you are though

    also i believe the more well versed people in lightning science call it a pulse current and not necessarily high frequency ac
    Normally current flows into and out of the plates of a capacitor rather than through it, but the physicists define an additional term called displacement current based on the rate of change of the electric field that lets you calculate as if current is in fact flowing through the capacitor.
    In the case of a charged capacitor with isolated plates (no external connections), current in the form of electrons (and maybe ions) actually does move from plate to plate.

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  6. #26
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    Quote Originally Posted by GoldDigger View Post
    Normally current flows into and out of the plates of a capacitor rather than through it, but the physicists define an additional term called displacement current based on the rate of change of the electric field that lets you calculate as if current is in fact flowing through the capacitor.


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    that's my understanding as well

  7. #27
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    Quote Originally Posted by GoldDigger View Post
    Normally current flows into and out of the plates of a capacitor rather than through it, but the physicists define an additional term called displacement current based on the rate of change of the electric field that lets you calculate as if current is in fact flowing through the capacitor.
    In the case of a charged capacitor with isolated plates (no external connections), current in the form of electrons (and maybe ions) actually does move from plate to plate.

    Sent from my XT1585 using Tapatalk
    That displacement current is what is happening when you connect a capacitor to AC voltage.
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