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6 comments
Participant

Join Date: Oct 2012
Posts: 2

Earthing

10/13/2012 12:02 AM

what is the earthing resistance and there value in min and Max?

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Guru
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#1

Re: Earthing

10/13/2012 12:11 AM

Zero to infinity. (resisting the urge to say "And Beyond")

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#2

Re: Earthing

10/13/2012 6:14 AM
The "earthing" resistance it is a notion according to BS7430 or IEC 60364 and it is equivalent to "Grounding Resistance" according to IEEE 80.
In above BS ch.7 "Factors involved in effective earthing" it is written:
"Earthing of either a system or equipment involves the provision of a connection to the general mass of earth.
These include the size and shape of the earth conductor, the soil in which it is buried and the connection of the system to it."
As lyn mentioned it, theoretically, could be from 0 to infinite.
Practically no minimum is required by any standard or official regulation but only the maximum is limited sometime by norms.
The earthing resistance has to be so reduced that the phase-to-earth or phase-to-earth-to phase short-circuit current could act the protection
and in the same time to limit the potential rise to a value less than a maximum permitted in order to protect the personnel which will touch the grounding system.
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#3
In reply to #2

Re: Earthing

10/13/2012 12:00 PM

Can you please check your post formatting settings? There are dividing lines coming through that break up your text as though it were in a spreadsheet. The information is good, but it is awkward to read.

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#4

Re: Earthing

10/13/2012 1:29 PM

I am really sorry for this inconvenient. I'll have to copy from excel to word previously.

The "earthing" resistance it is a notion according to BS7430 or IEC 60364 and it is equivalent to "Grounding Resistance" according to IEEE 80.

In above BS ch.7 "Factors involved in effective earthing" it is written:

"Earthing of either a system or equipment involves the provision of a connection to the general mass of earth.

These include the size and shape of the earth conductor, the soil in which it is buried and the connection of the system to it."

As lyn mentioned it, theoretically, could be from 0 to infinite.

Practically no minimum is required by any standard or official regulation but only the maximum is limited sometime by norms.

The earthing resistance has to be so reduced that the phase-to-earth or phase-to-earth-to phase short-circuit current could act the protection and in the same time to limit the potential rise to a value less than a maximum permitted in order to protect the personnel which will touch the grounding system.

I hope it is better this time.

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#5
In reply to #4

Re: Earthing

10/13/2012 1:35 PM

Yes, that looks better. Thank you, and GA. And welcome to CR4!

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Guru

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#6

Re: Earthing

10/21/2012 9:15 AM

No Standard on Earth - I repeat, no STANDARD on Earth (pun unintended) specifies a certain maximum persmissible value of earth resistance. Everywhere it is only specifies that it shall be "low enough" as to cause the protective device to operate in quick time - during an earth fault - before a person or a living being gets hurt.

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