In case of extension of an existing earthing system , client request automatic disconnection between new and old parts of the earthing grid to avoid mutual transmission of fault currents due to doubts on existing ancient earthing system good working.
My question is on the feasibility of separation and the relevant correct equipment to be used for such pourpose.
My personal knowledge is that the earthing system shuold be one and equipotential, so no separation is foressen by the international codes.
Can anyone help me??

many thanks