A shunt fault is a type of fault that occurs in

submarine communications cable A submarine communications cable is a cable laid on the sea bed between land-based stations to carry telecommunication signals across stretches of ocean and sea. The first submarine communications cables laid beginning in the 1850s carried te ...

s. Many such cables use underwater repeaters or amplifiers to boost signals being passed along the cable. These repeaters or amplifiers are powered from either end of the cable using Power Feed Equipment. This is achieved by applying a voltage to the metallic (usually copper or aluminium) core of the cable that surrounds the

optical fiber An optical fiber, or optical fibre in Commonwealth English, is a flexible, transparency and translucency, transparent fiber made by Drawing (manufacturing), drawing glass (silica) or plastic to a diameter slightly thicker than that of a Hair ...

. Typically both ends share the current generation with one end providing a positive voltage and the other a negative voltage. A

virtual ground In electronics, a virtual ground (or virtual earth) is a node of a circuit that is maintained at a steady reference potential, without being connected directly to the reference potential. In some cases the reference potential is considered to be th ...

point exists roughly halfway along the cable under normal operation. The amplifiers or repeaters derive their power from the potential difference drop across them. A shunt fault occurs when the cable insulation becomes damaged, such that there is a short circuit from the metallic core to the seawater directly. In this situation the apparent location of the

will move to the shunt fault location. As long as the power feed equipment farthest from the shunt fault has the capability of generating the additional voltage required to maintain the same current, the cable system will continue to carry traffic. This damage can be from

ship anchors A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...

fishing trawler A fishing trawler is a commercial fishing vessel designed to operate fishing trawls. Trawling is a method of fishing that involves actively dragging or pulling a trawl through the water behind one or more trawlers. Trawls are fishing nets tha ...

s, backhoe dredgers, currents dragging the cable along the sea floor, or even sea creatures. A repair will be scheduled at a convenient time whilst the cable continues to operate.

External links

* *{{cite web , title=Effective Subsea Cable Repairs , url=http://www.flagtelecom.com/media/PDF_files/Effective%20Subsea%20Repairs%20v1.2.pdf , accessdate=2007-06-09 , archiveurl = https://web.archive.org/web/20070403204132/http://www.flagtelecom.com/media/PDF_files/Effective%20Subsea%20Repairs%20v1.2.pdf , archivedate = 2007-04-03 Submarine communications cables