We present summaries of those generally accepted designs. The best way for equalization of potentials utilizes a suitable earthing system in the form of a ring or foundation earth. For this purpose the most effective earthing encloses the object to be protected. The potential increases on the earthing and on all earthed metal parts of the object relative to the zero potential at a distant point. It may reach a very high value but it does not cause any danger if the potential differences inside the object to be protected are limited.
Potential equalization is realized by the bonding of all extended metal objects.
It ensures the connection of all metal supply lines entering a building, including power and communication cables, to the lightning protection and earthing system by direct junctions across disconnection spark gaps, or arrestors in the case of live conductors. This recommendation is in addition to any made grounding electrodes, such as the lightning ground ring. However, in general, a low earth resistance is recommended. This effectively minimizes voltage differentials on the ground plane which exceed a value that will produce noise or interference to communications circuits. The resistance to earth of the earth electrode subsystem should not exceed 10 ohms at fixed permanent facilities.