BS eart electrode resistance

[Doggie]

Could somebody tell me where I can find the final resistance value an earth electrode should reach? Former BS where stating it, but now is everything confusing...
The sites I have to protect are Telecom's RBS (small antennae sites) power supplies, and there is a lot of confusion regarding the said value. Keep in mind that impedances are stated, but to explain and impedance to our Clients will not be easy... much better the resitance.
Thanks for the help.

 

[marktb]

Depends on the protection device. The better the protective device the greater the impedance can be - but ideally you want the impedance to be as low as possible so that you get maximum benefit from the protective device.