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The Main source earth loop impedance is high(with earth fault IDMT) , will the sub-main switch protected by the main switch?

simonNg

Hello there, I have a question about installation new 63A MCCB when the existing main source earth loop impedance is over the requirement 0.53Ohm. 

I am wondering if the new switch may be able to be protected by the building main switch 400A MCCB with IDMT Earth Fault protection relay.

Sorry for my clumsy English, I have also attached an image for a better explanation. 

Cheers!~

Parents
  • 0

    "tinkle a bit of the earth pit grounding, hoping to get the best result ."

    Is tinkling on the earth rods common practice? I can see how it might work.

    Grin

  • 0 in reply to OlympusMons

    yep it is, especially with military generator trucks, as is laying the rod in a puddle and then parking the trailer or the land-rover back wheel on it. Depends on how much of a hurry you are in .

    I suspect that there is a pithy  phrase for it, but right now it eludes me ;-)


    Mike

  • 0 in reply to mapj1

    Interesting!!! I didn't know that generator tucks need to laying rod for earthing.

    Normally, we clean off the earth pit and will replace the rod if required.

    For old building earth pits usually have a lot of junk, and sometimes people might steal the earth tape/cpc for money, so we do redo it often. Normally, after this work, the earth-loop will improve a bit.

      

Reply
  • 0 in reply to mapj1

    Interesting!!! I didn't know that generator tucks need to laying rod for earthing.

    Normally, we clean off the earth pit and will replace the rod if required.

    For old building earth pits usually have a lot of junk, and sometimes people might steal the earth tape/cpc for money, so we do redo it often. Normally, after this work, the earth-loop will improve a bit.

      

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