Optical cable lines lightning protection and strong current protection are achieved by avoiding, guiding or discharging them underground to prevent lightning and strong current from causing damage to the optical cable lines themselves, communication equipment and personnel. The purpose of this guide is to provide a basic overcurrent protection philosophy for insulated power cables. There are many reasons to monitor for overcurrent conditions, such as: Long-term system reliability is affected by the amount of current. HV lines that combine overhead line segments with underground cable segments require a carefully designed protection scheme in order to ensure safety while maximizing the supply KPIs such as SAIDI. Faults on overhead segments are normally momentary faults (caused by birds, branches, lightnings. GRW200 is advanced numerical feeder differential protection IED implemented on Toshiba's next generation GR-200 series platform.