Insulation morphology effects on the electrical treeing resistance

Samples of 220 kV cross linked polyethylene (XLPE) insulated cables were studied by means of video microscopy and electrical treeing tests. The morphology of extruded dielectric has been shown to be of importance. The tree initiation voltage level improved some 20% when the morphology was influenced by means of screw engineering. Crystal sheaves sizes were reduced with the help of improved melt homogeneity.