Simultaneous Measurements of Space Charge Distribution and External Current in Low Density Polyethylene

Abstract

Space charge distribution and external current in low density polyethylene (LDPE) under dc high electric field were measured simultaneously using an improved pulsed electro-acoustic (PEA) measurement system. They were usually measured independently using different devices. However, to investigate the relationship between the space charge behavior and the conduction current, it is necessary to measure them simultaneously in the same sample. Therefore, we developed an improved PEA system to measure them simultaneously. In this improved system, the space charge distribution and the external current measurements are carried out by alternate switching the current measurement circuit to the PEA measurement. As the result of simultaneous measurements, it is found when the external current increases during the injection and the traveling of the positive charge from the anode towards the cathode. To explain the phenomenon, we estimated a displacement current, a conduction current and a conductivity distributions in the sample from the results of the measurements. Moreover, we examined the relationship between those distributions and the charge behavior in LDPE.