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Muthuvel
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Number Earth Pit

09/25/2012 7:21 AM

How to calculate number of earth pit for neutral (plate) earthing?
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PWSlack
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#1

Re: Number earth pit

09/25/2012 7:38 AM

Just apply the principles embedded in British Standard 7671.

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lyn
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#2

Re: Number Earth Pit

09/25/2012 12:16 PM

In the USA it's NEC.
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wareagle
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#3

Re: Number Earth Pit

09/25/2012 2:08 PM

Usually it will be 2 ground rods unless you can show that the grounding impedance is less that 25 ohms. That figure came from a telephone company requirement.

PW does BS 7252 actually specify a specific number of electrode for special installations?
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TonyS
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#4
In reply to #3

Re: Number Earth Pit

09/25/2012 8:20 PM

BS 7671 doesn't specify transformer earthing arrangements. I've got the relevant reg's somewhere, but for the life of me I can't lay my hand on them. To be honest they are so open to interpretation each distribution company seem to have there own.

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wareagle
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#5

Re: Number Earth Pit

09/25/2012 9:24 PM

How about the customers wiring. Is there any requirements regarding the gnd electrode?
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pnaban
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#6

Re: Number Earth Pit

09/25/2012 11:49 PM

I have seen the utility having 3 earth pipes(about 6ins dia C.I) for a distribution transformer-1 for neutral,1 for transformer body and 1 for lightning arrester. They normally follow BS.

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67model
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#7

Re: Number Earth Pit

09/27/2012 3:35 PM

Search this section of CR4 for "Earth Grid" and similar. There is much previous posting. I got a reference to a pdf document ["Earthing - Myths and Facts" by Jayanta Khan of Larsen and Toubro Ltd, referencing BS, IEE, IEC etc guidance and presenting good design procedure] from CR4 and downloaded it. Sorry, but I do not have the web download source used then. After some searching now, I believe Document came from website apqi.org.in, reference 13041.pdf - you may need to register on that site to download it.

The design of an earth system will vary greatly depending on

  1. Required earth grid resistance.
  2. Resistivity of earth in which buried.
  3. Possible current into earth system.

- so no-one can answer your question without more information.

67model
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67model
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#8

Re: Number Earth Pit

09/27/2012 5:50 PM

You may find this useful....

http://s.pangonilo.com/index.php?sdmon=files/Earth_Rod_Resistance.pdf
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electricalexpert65
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#9

Re: Number Earth Pit

09/28/2012 9:56 PM

Calculation procedure is given in IS 3043.
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67model
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#10

Re: Number Earth Pit

09/29/2012 2:59 PM

A final point, Methuvel,

It is generally found, from the resistance formulae etc given that plates [which you mention], even if made of copper, are inferior in effectiveness and cost to the galvanised steel rods driven into the ground provided by specialist earthing suppliers.

Incidently, if you are still there, write some reply, if only "Thank you, and goodbye".
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Users who posted comments:

67model (3); electricalexpert65 (1); lyn (1); pnaban (1); PWSlack (1); TonyS (1); wareagle (2)

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