Excellent electrical properties of zinc-oxide varistors by tailoring sintering process for optimizing line-arrester configuration

Abstract

We optimized the excellent electrical performance of zinc-oxide (ZnO) varistors doping of aluminum and indium by tailoring the sintering process. The surface morphology, nonlinear volt ampere properties, capacitance–voltage characteristics, and dielectric analyses were carried out. At a given aluminum and indium concentration, the average sample grain size ($d$) increased as lengthening sintering time from 0.5 to 2.5 h. The voltage gradient ($E_{1\text{mA}}$) decreased from 602.4 V/mm to 356.7 V/mm. The residual voltage of the sintered varistors at the lightning impulse current ($8/20\ \mu\mathrm{s}$) decreased as the samples sintering holding time extended from 0.5 to 2.0 h. When the ZnO varistor was sintered for 1.5 h, the samples showed an excellent performance, with a reference voltage of 479.3 V/mm at 1 mA DC. When assembled in the line surge arresters, the obtained high-voltage-gradient ZnO varistors can decrease their length and residual voltage, which allows for better coordination of the line surge arrester with the insulators. This study has great significance to optimize line-arrester configurations and improve power-system stability.