Space charge and conductivity measurement of XLPE nanocomposites for HVDC insulation-permittivity as a nanofiller selection parameter

Abstract

Cross-linked polyethylene (XLPE) insulation is successfully used for high-voltage AC transmission. However, it is still under development for high-voltage DC application due to space charge accumulation, which distorts the internal electrical field distribution and leads to its aging/failure. Therefore, the space charge should be measured and carefully analysed. On the other side, conductivity measurement helps to forecast the degradation probability of the insulation. Higher conductivity represents the severe degradation. Nanofiller addition, such as SiO2, TiO2, MgO and so on (< 5 wt%), particularly surface-modified nanofiller due to its better dispersion significantly suppresses the space charge accumulation and conductivity. Nevertheless, the choice of suitable nanofiller has still remained a challenge. With this context, space charge and conductivity of XLPE-silica and XLPEmagnesium oxide (MgO) surface-modified nanocomposites are measured. This study proposes a parameter for nanofiller selection that will deliver optimal properties for the intended application. Results show that nanocomposites with higher nanofiller permittivity (i.e. MgO) have less space charge accumulation and low conductivity and are justified with the help of a band gap theory model.