Space charge dynamics in silica-based polyethylene nanocomposites

Space charge formation is a well known phenomenon that affects the overall dielectric properties of insulation systems. Space charge occurs when the rate of charge accumulation is different from the rate of removal and involves moving and trapped charges, which modify the electric field distribution within the material. As a result of this, the internal field within the dielectric is locally increased, which then leads to faster degradation and premature failure. Several techniques have been used to probe the space charge behavior of novel dielectric materials, especially in connection with the emerging topic of polymer nanocomposites - material systems that exhibit unique insulation characteristics due to the presence of nanometer-sized inclusions. In this paper, we report on an investigation into space charge dynamics in silica-based polyethylene nanocomposites, where the nanofiller has been modified with respect to its surface chemistry. For this, the pulsed electro-acoustic technique has been used. Experimental observations indicate that the incorporation of nanosilica into polyethylene results in homocharge development near both electrodes. However, with appropriate surface treatment of the filler, homocharges formation was successfully suppressed. Possible relationships between the space charge development and dielectric breakdown properties of the nanocomposites are discussed.