Critical Conductor Temperatures in Submarine Cables Equipped with Protection Pipes

Sammendrag

Submarine cables used in harsh environmental conditions are often strengthened by means of protective structures, in addition to the armour, for  enhanced mechanical durability. The added exterior protection shields the cable against damage during installation and operation. These, polymeric or
metallic protective structures, contribute to the temperature increase in the cables by reducing the natural cooling processes. 
In this paper are described investigations on the thermal conditions in and outside a three-phased armoured submarine cable equipped with a fully enclosed mechanical protection. The investigations are conducted through a full-scale experiment, including mitigation techniques. 
In the full-scale experiment, the effects of the protective pipe result in a temperature increase when compared to an experiment using a cable with no protective pipe. The measurements show that the addition of the mechanical protection may result in the phase conductor temperatures to reach and
exceed the critical 90 °C limit, even under otherwise normal operating conditions.
The effect of measures to mitigate the increase in phase conductor temperature was also investigated. At set intervals a symmetrical distribution of holes
were drilled into the protective pipe. This mitigation technique resulted in a temperature decrease of approximately 9 °C in phase conductor temperature.