Preliminary results of space charge injection under high Pressure in low-density polyethylene

Polyethylene is often used as insulation in HVDC cables. In order to reduce charge injection and thus increase cable time life, various interface barriers, such as fluorination, or bulk barriers, such as nano-filler compounds, can be used to modify the material properties at the atomic scale. At the atomic scale, the energy gained by an electron subjected to an electric field depends on its mean free paths. Reducing the mean free paths, reduces the gained energy as well, resulting in less material degradation. In this paper we investigate the charge injection process as a function of a high static pressure. Without adding foreign materials, the high static pressure is used to change the material properties. The mechanical deformation of the material, and thus the mechanical reduction of charge mean free path, has a direct influence on charge injection and migration in the material. Planar samples were subjected to up to 100 MPa and space charge measurements were carried out simultaneously with a system based on the Piezo-electric Induced Pressure Wave Propagation (PIPWP) method. Results are discussed and it is shown that high external pressure leads to less space charge injection.