What is the best way to protect an equipement against the lightning if we have a sandy ground?

Question

If we know that in summer a dry ground

and all classical methodsare inefficient like salt and carbon for example

Answer 1

First measure your current ground rod resistance to establish a baseline. Anything over 25 Ohms is a problem and 5 ohms or less would be ideal. (You will need a special ground rod resistance tester.).

For sandy soil electrolytic ground rods are usually the only effective ground rod soltion.  These are 20-30 foot long copper pipes  filled with a salt compound.   The salt is designed to leach out over time and help to form conductive pathways in the soil to further improve ground rod resistance.

A drill rig is necessary for installation. A 4-6 inch bore holed is dug the rod inserted in the bore hole and backfilled first with bentonite clay then sand or special filler.

The potentials from a lightningstrike are not only high voltage but high frequency as well.  Ground straps made of braided copper should be used  to bond equipment cases to the grounding system.   The surge voltages also tend of travel in a straight line and don't follow bends well.    Keep ground wire as straight as possible and avoid sharp bends.

Surge suppression equipment is only as effective as the ground system it is connected to. With a poor ground the surge cannot be drawn away from the protected circuit fast enough.