THERMALLY STIMULATED DISCHARGE CURRENTS IN CORONA-CHARGED ARAMID PAPER

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 carrie d out on paper thicknesses of 76 and 1 27 mum using a point-plane gap in air at atmospheric pressure. TSD currents were measured over a temp erature range of 0-200-degrees-C and the influence of various paramete rs, such as the poling voltage, rate of heating and effect of electrod e materials, were investigated. Corona-charged aramid paper with posit ive polarity voltage showed that the TSD current is of either polarity depending upon the temperature range. Three distinct peaks were obser ved, one in the low-temperature range, 20-25-degrees-C, and the other two peaks at higher temperatures. The low-temperature peak was conside red to be due to an abnormal TSD current, whereas the currents at high er temperatures were normal TSD currents. Activation energies were det ermined using the low-temperature tail of the TSD curves and were foun d to be dependent on extrinsic parameters such as the thickness of the sample. The activation energy for aluminium electrodes was observed t o be in the range of 0.5-2.0 eV. The TSD currents for the low-temperat ure peak was considered to be electronic. It is postulated that the ch arge carriers are generated within the material by the intense electri c field due to corona.