The XLPE cable should at least have a conductor cross section adequate to meet the system requirements for power transmission capacity. The cost of energy losses can be reduced by using larger conductor. Load losses in XLPE cables are primarily due to the ohmic losses in the conductor and the metallic screen. XLPE cables can be loaded continuously to a conductor temperature of 90°C. The dielectric losses of XLPE insulation are present also at no load. Those losses depend on the operation voltage applied and shall be considered above 100 kV. Dielectric losses in XLPE cables are lower than for EPR and fluid-filled cables. The current rating of submarine cables follows the same rules as for land cables. However there are some differences:
− Three-core submarine cables usually have steel wire armour. Single-core cables have non-magnetic armour.
− Single-core cables can be laid separated or close. Close laying gives lower losses. Separation eliminates mutual heating but means higher losses in the armour. The induced current in the armour can be high, up to the same value as in the conductor.