Influence of space charge related to water trees on the breakdown voltage of power cable insulation

A three-dimensional computation of the electric field and breakdown voltage in power cable insulation containing water trees and space charges is presented. The breakdown voltage and the conductivity of cylindrical samples of cable insulation containing water trees were measured. The samples have been aged in wet environment under ac voltages of frequencies comprised between 1 and 5 kHz. Exponential and parabolic spatial variations of permittivity and space charge density and the electrostatic, electro-kinetic and quasi-stationary regimes of the electric field were considered. The best correlation between the experimental breakdown voltage and the calculated one has been obtained in quasi-stationary regime.

► Electric field computation in treed cable insulation in the space charge presence.
► Electrostatic, electro kinetic stationary and quasi-stationary regime are considered.
► The time variations of the conductivity and permittivity are taken into account.
► Breakdown voltage experimentally obtained is compared with the computed one.
► The best correlation is obtained for electro kinetic quasi-stationary regime.