Dielectric model of water trees in an XLPE cable

Abstract

In this paper a water-tree degraded insulation is modeled as a matrix composed of cubic cells. In the model there are three types of cells: pure XLPE, XLPE with water inclusion and the XLPE cell with a cylindrical water channel. Voltage dependant dielectric properties of the water-trees are modeled by an elongation of the inclusions and appearance of the conducting channels caused by the Maxwell stress. Afterwards the modeled effective permittivity of the insulation matrix is compared with the dielectric spectroscopy measurements of a field aged XLPE cable.