ITU-T Recommendations

Recommendation ITU-T K.46 specifies a procedure to protect telecommunication lines using metallic symmetric conductors against overvoltages and overcurrents imposed on the lines due to nearby lightning discharges. The protection procedure is related to the exposure of the line to the effects of nearby lightning discharges, and includes the earthing and bonding of the cable shield and the installation of surge protective devices (SPDs).This Recommendation follows the risk management procedure which requires that the expected risk of damage due to both direct flashes and flashes near a telecommunication line shall be not greater than the tolerable risk. The user shall refer to Recommendation ITU-T K.72 for the risk management procedure.The risk assessment is limited to the failure of insulation of telecommunication lines (buried or aerial cables, shielded or unshielded cables) which can cause the loss of service.The user shall refer to Recommendation ITU-T K.47 for evaluating the expected risk of damage due to direct lightning discharges, either to the line itself or to the structures where the line enters, and, if necessary, in order to select the protection measures to reduce the risk of damage due to direct flashes.Examples of application of this Recommendation are reported in Appendix IV.