TSC Characteristics of Aged ZnO Varistors under Different Applied Voltage Ratios

ZnO varistors have high nonlinearity, which are widely utilized in protecting power systems and electronic devices against the dangerous over-voltages or surges, and the ac aging characteristic of ZnO varistors is widely concerned. In this paper, the thermally stimulated current (TSC) characteristic, U-I characteristic and power loss characteristic performance of aging ZnO varistors have been investigated in different conditions. The experimental results show that with the increase of aging voltage, the power loss increases, U-I characteristic drifts, the trapped charges experimented by TSC increase that causes the decrease of the height of Schottky barrier aggravating, which would lead to the aging of ZnO varistors; the trend of power loss characteristic and U-I characteristic is consistent with the trend of TSC characteristic. Consequently, the thermally stimulated current experiment is an effective method to present the aging degree of ZnO varistors.