Influence of Nanofillers on Resistance to Water Tree in XLPE Nano Composite

Cross-linked Polyethylene (XLPE) cables are widely used for medium voltage underground cables these days. However, void and impurity defects have been a major reason for the failure of cable insulations as these defects induce internal discharges and cause a significant change in the dielectric properties of the insulation. The objective of this paper is to investigate the effect of nanofillers in inhibiting water tree propagation. This is done by calculating electric stress at different points in unfilled XLPE and XLPE nanocomposite. For that various analyses are conducted viz. study and comparison of the electric field stress distribution in unfilled XLPE with the presence of water voids with and without nanofiller. It is found that the field effect is more at the edges of the ellipse shaped water voids. Water voids which experience the maximum electric field, form channels and lead to break down. Addition of nanofillers delays the path of electric field distribution and increases the breakdown strength. In this study four types of nanofillers are considered with different weight percentage loading. Electric field distribution has been varying for different weight percentage of nanofillers. Due to the high interface/volume ratio in nanocomposites, it is found that nanocomposites have higher resistance to water tree growth and scattering in the interfacial region inhibits tree growth.