Space Charge Formation in LDPE/MgO Nano-composite Film under Ultra-high DC Electric Stress

Abstract

Space charge characteristics under high DC electric field of more than 100 kV/mm in a nano-composite film of the low density polyethylene (LDPE) mixed with a nano-size filler of MgO were studied using a pulsed electro-acoustic (PEA) method. To measure the space charge distribution using the PEA system under the high electric field in a thin film, a spatial resolution of the PEA system was improved. Using the improved system, the time dependence of space charge formation in LDPE and LDPE/MgO nano-composite under the high electric field was observed. It is found that a huge amount of packet-like charge generation in LDPE makes a local electric field in the bulk higher. On the other hand, there is almost no such huge packet-like charge observed in LDPE/MgO with MgO content of more than 0.5 phr, while it was observed in that of 0.2 phr. It is found that the generation of the packet-like charge under the high electric field strongly depends on the content of MgO in the LDPE/MgO nano-composite.