Computer simulation on formation of space charge packets in XLPE films

The packet-like space-charge behavior in an oxidized crosslinked polyethylene (XLPE) film doped with antioxidant is discussed through computer simulation. The model is based on the following assumptions, (1) both electrons and holes are injected from the electrodes and they migrate to the opposite electrodes by hopping transport, (2) holes are also supplied from acceptor sites depending on the field, (3) the holes are excited to the hopping level only via an intermediate level. In this model, a space-charge packet is not caused by the excess of mobile electrons but by the deficiency in mobile holes. The ionized accepters left behind by hole migration form an apparent negative space charge packet and it propagates towards the anode as the high field region moves.