Calculation of the transmission capacity of long-distance EHV single-core submarine cable systems

A general calculation method for the analysis of transmission capability of a long-distance single-core AC submarine cable system is presented. The method is based on modal transformation of voltages and currents in multiconductor cable systems. Using this method, numerical calculations on 500kV submarine cable systems have been performed with particular reference to the effect of the distance between bonds connecting metallic sheath, outer conductor and armour on the transmission capacity of the system. It was clarified by the analysis that the transmission capcity of the system increased with decreasing bond intervals. Examination of the current distributions between various conductors along the length showed that this increase of transmission capacity was mainly due to the dispersion of the charging current into the metallic sheath, outer conductor and armouring at the bonding points. Finally, analytical results for the transmission capacities of long-distance 500 kV single-core oil-filled submarine cable systems are given by comparing the two cases of single-armoured and double-armoured cables