Anomalous Discharging Currents due to Space Charge

Abstract

Discharging currents caused by the migration of space charge (e.g. due to electrons injected from the electrode) after removing an applied field were numerically calculated under various conditions. The calculated discharging currents flowed in the opposite direction to the charging current under the condition of ohmic electrodes, while the blocking electrodes resulted in the anomalous discharging currents flowing in the same direction as the charging current. The behaviors of the anomalous discharging currents are discussed in detail and they are in good agreement quantitatively with the experimental data obtained for high-density polyethylene. The temporal changes in the distributions of space charge and internal field, and the contribution of diffusion to the currents were also revealed.