Application of Finite Element Analysis to externally forced water cooled cable circuit ratings

In order to increase the available current carrying capacity of high voltage cables, utilities may employ forced water cooling within power transmission networks to remove the heat from cable groups. For example the transmission network of England and Wales includes externally forced cooled circuits, i.e. cooled by pumping water through pipes buried in the vicinity of high voltage transmission cables. At the present time a simple and expedient computer program is used to rate these circuits. This model is similar to that of Electra 66. To attribute confidence limits to cable ratings attained using this method an extended 2-D heat-transfer FEA model has been constructed to allow the calculation of the cable core temperature for a typical water-cooled three-phase circuit of three single-core cables buried in flat horizontal arrangement within a backfilled trough. A sensitivity analysis of the model to changes in ac resistance, burial depth, dielectric loss, soil thermal resistivity and surface boundary condition has been performed and is presented.