Grounding PV system

Discussion in 'The Projects Forum' started by Cerkit, Jul 4, 2013.

  1. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Hi, can someone explain the effect of grounding the positive or negative conductor of a PV array. I guess in many ways I view it as though grounding the positive or negative of a battery terminal, how does this affect the voltage between the terminals?
    I guess from an intuitive perspective what exactly happens, because the electrons can then flow from the ground? Bit confused here.

    Any explanation would be very much appreciated.

    Thanks!
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    It has absolutely no effect on the voltage between the terminals.

    What is does is insure that one of the terminals is at ground potential, which is typically the potential of your feet, thus making any an accidental contact with either conductor safer.

    Well... I'm going to ignore the electrons and just talk current. A grounded solar installation compliant to the National Electronic Code (NEC or just "to code") has three wires just like an AC outlet: hot, neutral, and ground.

    Somewhere in one single place, neutral and ground are connected together. A single connection is used to keep stray current out of the ground lead: it is just there for faults. So anywhere you find neutral it will be very close in voltage to ground.

    The hot lead may be either + or - and still meet code, though + is more common.

    Current still flows + to - no matter where ground is connected.
     
  3. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    If by ground you mean the 'safety' GROUND connected to a ground rod or central grounding point in a building there is no effect on current flow during normal operation because the grounding wire is not a 'hot' conductor during normal operation.

    ftp://sunsite.unc.edu/pub/academic/...ces/homepower-magazine/archives/18/18pg26.txt
     
  4. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    I am referring to tieing the plus or minus DC to ground. Not about earthing for protection.

    Thanks
     
  5. MrChips

    Moderator

    Oct 2, 2009
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    You can connect the -ve terminal to ground or you can choose to leave it not grounded. Makes no difference except for safety reasons.
     
  6. ErnieM

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    Apr 24, 2011
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    You keep using that word. I do not think it means what you think it means.

    You would need to explain what YOU mean by "ground" in this context to receive any kind of reasonable answer.
     
  7. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Connecting to an earth rod nearby.
     
  8. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    Your inverters should already be tied to ground so it does not need to be done at the panels.

    If your inverters are in isolated type (designed not be to grounded) then you don't ground your panels either.

    In both cases you don't ground any wire connection to the panels.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
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    This is one of the problems, 'Ground' is banded about for any power supply common, regardless.
    Chassis or Logic common, may, or may not be connected to Earth Ground.
    Max.
     
    Last edited: Jul 23, 2013
  10. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Hence why I am trying to clarify that I am talking about connecting the conductor to ground. (Not the frame of the modules or the frame of the inverter)
     
  11. MrChips

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    The purpose of Earth Ground is to conduct charges on the frame or chassis to ground. This is a safety feature.

    You can leave the PV voltage "floating".

    AC/DC wall adapters are usually "floating".
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    In rare instances Earth Ground is used as a conductor, but the more common approach is to use earth ground as a Reference or 'Neutral' , but not a circuit conductor per se.
    IOW all circuit functions are fed by assigned conductors direct from the respective supply.
    Whether AC or DC either of the supply terminals can be referenced to earth ground, although in the case of DC, it is usually the -ve side of the supply.
    Max.
     
  13. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Ok. Of course you wouldn't use the earth conductor as 'the' conductor in any case but you can reference the -ve or +ve to ground. What I am unclear about is if the +ve DC side is referenced to earth don't electrons from the earth immediately fill the holes created in the modules?
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    An electrical circuit requires a complete circuit (return path), if no path provided there should be no flow of electrons?
    The are examples, past and present where earth ground is/was used as a conductor, electric fencing is one example, and around the 1900's, rural telephone systems used one wire with ground conductor return.
    Max.
     
  15. MrChips

    Moderator

    Oct 2, 2009
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    You can connect the +ve or -ve side to earth.
    Forget about what happens to electron or charge flow.
    All it means is that the terminal that is connected to earth is now at a reference potential, i.e. earth potential, whatever that may be. It is all relative.

    It is like saying my swimming pool is now at sea level. There is no flow of water between the pool and the sea.
     
  16. Cerkit

    Thread Starter Active Member

    Jan 4, 2009
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    Thanks for all your help. Has made things clearer.
     
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