The self-contained oil-filled cable has been developed to meet increasing power requirements both in terms of voltage and ampacity. The paper gives details of power transmission capability for 230, 345 and 525 kV cable systems for a variety of natural and forced cooled conditions. The highest rating is obtained with internal oil cooling and at 525kV 4000 MVA can be transmitted using one cable per phase. Details are given of accessory design features that have been adopted to ensure that these components do not become a limitation to power transmission capability.