Shunt fault

From Wikipedia, the free encyclopedia

A Shunt fault is a type of fault that occurs in submarine telecommunications cables.

Many such cables use underwater repeaters or amplifiers to boost signals being passed along the cable. These repeaters or amplifiers are necessarily powered, and this is achieved by applying a voltage to the metallic armouring of the cable. The amplifiers or repeaters are powered by a current generated by the potential difference between the cable armour and the surrounding seawater.

A shunt fault occurs when the current carrying armour has its insulation damaged, such that there is a short circuit from the metallic armour to the seawater directly, bypassing the amplifier or repeater. This damage can be from ship anchors, or fishing trawlers, or even sea creatures.

For this reason, it is usual to design the cable system to allow voltage to be applied to the cable at either end of the cable segments, so a single shunt fault does not prevent continued operation. This allows a repair to be scheduled at a convenient time while the cable continues in operation.