Novel ZnO Varistors for Dramatically Improving Protective Effect of Surge Arresters

Abstract

The insulation level of power apparatus is based on the protection level of overvoltage in power systems. Deeply suppressing the switching overvoltage of UHV systems will reduce the manufacturing cost and technical bottlenecks of UHV power apparatus. We studied the effects of multielements doping on the electrical properties of ZnO varistors co-doped with Al2O3, Ga2O3, and In2O3 Scanning electron microscopy, current–voltage testing, capacitance–voltage testing, and X-ray diffraction were performed. The results showed that the residual voltage ratio of sintered varistors decreased as the indium dopant concentration was increased. The samples with 0.03 mol % indium, 0.2 mol % aluminum, and 0.42 mol % gallium showed excellent overall performance, exhibiting a nonlinear coefficient of 61.2, a leakage current of 1.63 $\mu A /cm2$, a 1-mA residual voltage of 435 V/mm, and a residual voltage ratio of 1.52. These optimized properties will be of great utility in the manufacture of metal oxide arresters. The protective effects of this kind of novel surge arresters for lightning and switching overvoltage in UHV systems are analyzed. With the low residual voltage ZnO varistors applied to surge arresters will dramatically improving the protective effect of surge arresters, to realize the target to deeply suppress the lightning and switching overvoltages, and then reduce the insulation level and manufacturing bottleneck of UHV power apparatus.