Numerical Simulation of Space Charge Injection in LDPE under Relatively Low Electric Stress

In this report, we tried to simulate the behavior of space charge injection in low-density polyethylene (LDPE) under relatively low electric stress. In our previous paper, we found an interesting packet-like charge behavior in LDPE under high DC electric field of more than 100 kV/mm. It is thought that the huge packet-like charge must strongly affect to breakdown characteristics of LDPE. To analyze the feature of the packet-like charge behavior in LDPE, we have carried out a simple numerical simulation based on the experimental results in the previous paper. In the proposed model, by giving a few parameters of the sample, we can easily simulate the packet-like charge behavior. To investigate which parameter is dominant for the packet-like charge behavior, we attempt to apply our proposed model to various kinds of polyethylene which show different packet-like behavior from that in LDPE. However, the space charge accumulation process in LDPE under around or below 100 kV/mm has not explained using the model yet. From the experimental results, it was identified the space charge spread uniformly in the bulk under relatively low electric stress. To explain the behavior using the proposed model, it is necessary to concern the complicated parameters of charge injection and conductivity distribution. Therefore, as a first step, we tried to fit the numerical simulation results to the actual experimental results.