Calculation of losses in electric power cables as the base for cable temperature analysis

Abstract

Power losses refer to the heat generated in cable conducting parts (phase conductors and sheaths) and in cable insulating parts. It is necessary to know the exact data regarding heating powers for the calculation of heath transfer and cable temperatures. Heating power in phase conductors and sheaths mainly depend on current values. Exact calculation of those powers is very difficult. This paper develops a mathematical model of heating power calculation in three phase single-core cable conductors and sheaths. This model is used to determine filament currents and heating powers in phase conductors and sheaths. Geophysical features of the cable route are also considered. Three-phase single core electric power cables of 35 kV rated voltage are taken as an example. Two laying conditions (trefoil and flat formation) are considered. Sheathes are bonded and grounded at both ends. Calculation results for cables in flat configuration show that heating powers in cable sheaths do not have equal magnitude and increase with distance. The least heating power occurs in the sheath of the middle cable. Heating powers in sheaths of outer cables are of unequal magnitude too