What are the recommended resistances for different levels of earthing pits?

[i.mehrzad]

There are different levels of earthing pits. Like transmission stations, local substations, etc. Can someone specify the resistances of the earthing pits that each of them in level should actually have.

 

[m.s.j]

Earth pit can be a portion of earthing systems although it can be a grounding system entirely.
For typical amount of grounding systems you can refer to Grounding riddle No.19 from http://electrical-riddles.com

Are you iranian?

 

[i.mehrzad]

I read that earthing pits should be around 5 ohm for transmission stations, and 2 ohms for distribution station.