Gunnar Berthelsen gunnar.berthelsen@nexans.com
HIGH RELIABILITY – LOW COST SUBMARINE CABLE DEPLOYMENT
the coastline ou most dreaded s has been impe one. There organizations a large number organizations, be avoided. H find a route av often had to ma
Abstract: A method is developed to utilize the 6450 solutions are0605 expensive even for long systems, and Nexans Norway AS, PO.Box Etterstad, Oslo, Norway. topology A ofmethod the seabed and a to detailed discussion with veryand short coastaldiscussion cables (each in permitting the order parties Abstract: is developed utilize the topology of the seabed a detailed with the with the permitting parties to protect the submarine of some km’s up to 70 km) the cost would be to protect the submarine cables, so that burying has become un-necessary. cables, so that burying has become un-necessary. phenomenal. Thus, a concept has been developed (where cables be avoided and other commercial 11 INTRODUCTION INTRODUCTION are not buried) baseddue on to fivefishing principles: activity In most most parts parts ofofthe theworld worldsubmarine submarine systems In systems are are protected by burial of heavy cables into • Cable protection achievedby detailed by detailed protected by burial of heavy cables into the seabedthe to • Cable protection is achieved mapping of different depending the risk on of the external the allowable areas in order toparties identify route where seabed todepths, different depths, on depending risk discussions with the permitting to adefine damage. Normally veryNormally heavy cables andheavy deep burial is thethat cable is protected by thedue seabed topology of external damage. very cables areas must be avoided to fishing and used in shallow waters, choosing gradually lighter and deep burial is used in shallow waters, choosing other commercial activity • The protection is so successful that a lighter-thancables and shallower burial as the water depth gradually lighter cables and shallower burial as normal cable can be used increases. This leads to very high costs in installing the water depth increases. This leads to very high • Cable protection is achieved by detailed repeater-less submarine systems, which are normally • The cable is installed with a very high accuracy costs in installing repeater-less submarine systems, mapping allowable route areas in order to deployed in “shallow” waters. relativeofto the the pre-defined which are normally deployed in “shallow” waters. identify a route where the cable is protected by Norway has a coastline of more than 22.000 km with • seabed As the route lengths are short and the cables light, the topology many deep fjords and dotted islands along the coast, so very small, dedicated cable ships can be used. Norway has a coastline of moreway thanof22.000 km submarine cables is a natural deploying 2 protection ROUTE SELECTION with many deep fjords and dotted islands along • The is so successful that a lighterbroadband networks. (Fig 1) the coast, so submarine cables is a natural way of thannormal canfishing be used Norway hascable a huge industry, which works from deploying broadband networks. (Fig 1) the coastline out to the oceans, and since fisheries is the • The cable is installed a verytohigh accuracycable it most dreaded source with of damage a submarine has been imperative to co-operate with them from day relative to the pre-defined route
one. There are local and regional fisherman’s all along the coast, so there have been a • Asorganizations the route lengths are short and the cables large number of detailed discussions with these light, very small, dedicated cable ships be should organizations, in order to determine whichcan areas used. be avoided. However, it has always been possible to find a route avoiding fishing areas, but the cable has often had to make significant detours. 2 ROUTE SELECTION
by Gunnar Berthelsen 27
Fig 1: Map of Norway
However, it was very early (1985) realized that “normal” cables and heavy However,methods it was involving very earlyheavy (1985) realized that burial equipment would make the submarine solutions “normal” methods involving heavy cables and non-viable. This due to thewould fact that such are heavy burial equipment make thesolutions submarine expensive even for long systems, and with very short solutions non-viable. This dueoftosome the fact coastal cables (each in the order km’sthat up such to 70 km) the cost would be phenomenal. Thus, a concept has been developed (where cables are
When it has be to deploy the modern charts data. The na recently mappe means, and ch high resolution
Norway hasitahas huge fishing industry, which When been determined which areasworks can be used from to thedeploy coastline out to the oceans, and is since the cable the route selection based on fisheries is the mostgenerated dreadedfrom source of damage to modern charts multi-beam echo-sounder data. The national cartographic organization a submarine cable it has been imperative to co- has recently mapped a large of thearecoast operate with them from day portion one. There localby such means, and charts are therefore available with a very and regional fisherman’s organizations all along high resolution (objects <1m can be identified). Where the coast, so there have been a large number of data are not yet available, new data has to be generated detailed discussions with these organizations, in specifically for the project using the same technology. order to determine which areas should be avoided. Using these high resolution charts the cable route is However, it has always been possible to find a route selected, placing the cable in the “valleys” of the avoiding fishing areas, but the cable along has often hadslopes, seabed, avoiding deployment steep to make significant detours. avoiding ship wrecks, etc. (Fig 2)