DC conduction and electrical breakdown of MgO/LDPE nanocomposite

To understand basic electric properties of nano-sized magnesium oxide (MgO)/low-density polyethylene (LDPE) nanocomposite under DC voltage application, the volume resistivity, the space charge distribution, the breakdown strength and the short circuit tree were investigated. By the addition of nano-sized MgO filler, both the DC breakdown strength and the volume resistivity of LDPE increased. At the average DC electric field of about 120 kV/mm, a positive packet-like space charge was observed in LDPE without MgO nano-filler, whereas a little homogeneous space charge was observed in MgO/LDPE nanocomposite material at the front of electrode. The initiation probability of short circuit tree is decreased by addition of MgO nano-filler. And also, the length of short-circuit tree in the film with MgO nano-filler is shorter than that without MgO nano-filler. From these results, it is confirmed that the addition of MgO nano-filler leads to the improvement of DC electrical insulating properties of LDPE.