Simultaneous measurement of space charge and conduction current on LDPE/MgO nanocomposite

In this paper, the simultaneous measurement of the space charge and conduction current were performed under constant DC field or increasing a dc ramp field to comprehend the breakdown phenomena of LDPE/MgO nanocmoposite. In the measurement under a dc constant field, the conduction current on LDPE increased clearly due to the positive charge injection by enhanced local field at the anode with negative charge formation in the bulk. The conduction current on LDPE/MgO nanocomposite with MgO content of 1 phr also increased slightly due to hetero space charge effect at the anode. In case of the measurement under DC ramp field, the conduction current on LDPE increased monotonically with increasing average field with increase of amount of negative space charge in the bulk. The field at which the conduction current on LDPE/MgO nanocomposite with MgO content of 1 phr showed rapid increase agreed with that at which a positive charge turned to decrease. From these results, it was suggested that the conduction current controlled by the space charge near the electrodes due to charge trapping of MgO nanofiller, brought the breakdown.