In the case of earth fault in high or medium voltage a.c. network significant earth potential rise (EPR) can occur in the earthing structure where the current is discharged to the earth, typically in the earthing grid of substation involved in the fault. When the earthing grid is connected metallically to long conductors like earth wires, neutral conductors, counterpoises, cable sheaths, pipes and rails, the EPR can be transferred far away well beyond the zone of influence. This Recommendation describes the mechanism of potential transfer to the customer's premises with special view of the transfer through the neutral conductor of the low voltage network and the sheath of the telecommunication cable. Calculation techniques are given for the determination of the magnitude of EPR and transferred potential. Mitigation techniques for preventing the transfer of EPR are proposed. Different isolation techniques are proposed as possible mitigation applicable in the telecommunication plant.