Estimating transmission line parameters of three-core power cables with common earth screen

The propagation modes of travelling wave in a threecore power cable (XLPE or PILC) with common earth screen can be uncoupled into three modes: one shield to phase (SP) mode and two phase to phase (PP) modes. A generic model approach is applied in this paper to estimate the transmission line parameters of three-core cables with common earth screen, which includes the effect of different layers on series impedance and admittance. The characteristic impedance, the propagation velocity and the attenuation for SP and PP modes of two cable types, PILC and XLPE are modeled and compared with test results. Calculated parameters match within 5% for the characteristic impedances of different modes and 5% for the velocity for the PILC cable. Larger deviations occurred for XLPE cable, due to difficulties in appropriate modeling the semiconducting insulation screens around each conductor. The attenuation for both PILC and XLPE is hard to predict because data on complex permittivity, being the dominant factor, is hardly known.