Evaluation of space charge accumulation processes in small size polymeric cable models

Polymeric insulation materials have not been used in HVDC cable systems until recently because of the tendency of polymers to deplete accumulated charges very slowly. Research on space charge injection, conduction and trapping mechanisms can reveal information about which new materials are the best candidates for HVDC cable insulation. In this paper, the space charge accumulation processes are evaluated in mini cable models consisting of several different XLPE based insulation materials and PE based semi-conductive layers. The main difference between the materials can be found in the type and concentration of additives. The influence of the semiconductor-insulation interface on the space charge accumulation threshold is investigated with the help of polarization characteristics obtained with space charge measurements conducted with the Pulsed Electro-Acoustic (PEA) method for cable geometry objects.