connecting equipment and arrester to earthing mat 1

[simatic7]

Hi all
I just have a question in the mind as I read in a book that arrester common (neutral) and equipment neutral should not be connected together ?
can anyone please give the reason why these two neutrals can not be connected together and what is the hazards during the lightning if they are connected together ?
thanks

 

[waross]

One thing to be avoided is connecting the arrester conductor to an equipment neutral or neutral grounding conductor ahead of the ground grid.
The impedance of a conductor as seen by the steep wave front of a lightning strike may be many times the simple resistance of the conductor. That impedance times a large current will produce a voltage difference in accordance with Ohm's law.
Should an equipment ground or a system neutral share a conductor with an arrester, the voltage drop between the grounded equipment and the ground grid caused by a high current surge, such as a lightning strike, may develop lethal voltages between grounded equipment surfaces and true ground.
A man standing on the ground beside a grounded piece of equipment that is sharing a conductor with an arrester may experience a lethal touch voltage. That is often a once in a lifetime experience.

Bill
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"Why not the best?"
Jimmy Carter

 

[simatic7]

Thanks Bill. It seems its a simple answer but to me its a great answer in a very clear and simplified way.
Thnaks a lot.
Simatic7

 

[waross]

Thank you simatic. I appreciate your kind words.
Yours
Bill

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[prc]

Waross,That is a good explanation deserving a star !