Space Charge Formation in Low-density Polyethylene up to Breakdown Influenced by Addition of MgO nano-filler under DC Ramp Voltage

To understand the space charge formation of nanosized magnesium oxide (MgO) / low-density polyethylene (LDPE) nanocomposite materials, the space charge up to the breakdown has been investigated under DC increasing ramp field. A negative charge was dominated in 0 phr sample. A positive charge was dominated in nanocomposite sample. The field increment (= the maximum field - the average field) of 0 phr increased with increasing average field and then was saturated with a few rises and falls before the breakdown. In case of 1 phr sample, after showing the peak, the field increment turned to decrease with further increase of the average field. In case of 2 phr and more, the clear decrease of the field increment was not observed due to a few positive charges. The space charge distributions of 1 phr shows different distribution between 1 st and 2 nd filed applications while that of 0 phr did not. From these results, it was considered that the homo space charge effect at the anode brought by charge trapping effect of MgO nanofiller controlled the space charge formation in nanocomposite..