Improving the protective effect of surge arresters by optimizing the electrical property of ZnO varistors

Abstract

In the present research, we studied ZnO varistors having multiple dopants and optimized their microstructure and electrical properties by tailoring the sintering process. At certain concentrations of the rare-earth elements yttrium and indium, the voltage gradient decreased from 683.7 to 293.0V/mm as the sintering temperature was increased from 1160 to 1320°C. In addition, the nonlinear coefficient first increased and then decreased as sintering temperature was increased. When sintered at 1240°C, the multiple doped ZnO varistors samples showed excellent performance, exhibiting a voltage gradient of 520V/mm, a residual voltage ratio of 1.55, and a density of 63.7A/cm2 under a current waveform of 8/20μs, and a nonlinear coefficient of 74.5. These optimized properties will be of great utility in the manufacture of metal oxide arresters. When the high-performance varistors were used in surge arresters of ultra-high voltage grids, the overvoltage level along the transmission line and in the substation were reduced by 31.14% and 33.53%, respectively. This combination of characteristics will dramatically improve the protective effect of surge arresters for deeply suppressing over-voltages in power systems, significantly reduce the insulation requirement and cost of power apparatus as well as greatly increase the safety of power systems.