Study on Space Charge Characteristics during Aging Process of DC ZnO Varistors

ZnO varistors are widely used in UHV arrester, the properties of ZnO varistors affect the safe and stable operation of the system, and there are relatively few micro characteristics of the aging process of dc ZnO varistors. In order to research the aging process of DC ZnO varistors, an aging experiment based on the actual working condition of UHV DC arrester is designed, combined with conventional Scanning Electron Microscope (SEM), Energy-Dispersive Spectrometer (EDS) and volt-ampere characteristic test, the ZnO varistors aging mechanism has been discussed from the perspective of space charge and barrier height change in this paper. Volt-ampere characteristic test and Scanning Electron Microscopy (SEM) aging test have found that AC and DC aging have obvious characteristic differences, The results of energy spectrum analysis revealed that there was the migration of zinc ion and Bi cation in the process of direct current aging, and has obvious accumulation phenomena in the single side. Space charge test results show that as the aging time increases, the space charge accumulates, and the surface charge density, the trap energy level and the trap charge are also increased, and the height of schottky barrier is obviously reduced, making the macroscopic electrical properties changes.