Thermally stimulated discharge currents in corona-charged aramid paper

Abstract

Thermally stimulated discharge (TSD) currents were measured in corona-charged aramid paper to study the mechanisms of charge storage and its subsequent release from the bulk of the material. Studies were carried out on paper thicknesses of 76 and 127 μm using a point-plane gap in air at atmospheric pressure. TSD currents were measured over a temperature range of 0–200 °C and the influence of various parameters, such as the poling voltage, rate of heating and effect of electrode materials, were investigated. Corona-charged aramid paper with positive polarity voltage showed that the TSD current is of either polarity depending upon the temperature range. Three distinct peaks were observed, one in the low-temperature range, 20–25 °C, and the other two peaks at higher temperatures. The low-temperature peak was considered to be due to an abnormal TSD current, whereas the currents at higher temperatures were normal TSD currents. Activation energies were determined using the low-temperature tail of the TSD curves and were found to be dependent on extrinsic parameters such as the thickness of the sample. The activation energy for aluminium electrodes was observed to be in the range of 0.5–2.0 eV. The TSD currents for the low-temperature peak was considered to be electronic. It is postulated that the charge carriers are generated within the material by the intense electric field due to corona.