Surge Arrester with High Performance Metal Oxide Varistors for Deeply Suppressing Overvoltage in AC UHV Systems

Overvoltage and its protection are the key problems for power system. For ultra-high voltage system, switching overvoltage is the key factor of the insulation standard of power system. The suppression of the switching overvoltage in ultra-high voltage systems will reduce the manufacturing cost and technical bottlenecks of ultra-high voltage power apparatus. This paper studied the influence of multi-elements doping on the electrical performance of zinc oxide varistors. The easurment of scanning electron microscope, electric field-current density characteristics from small to large current region, capacitance-voltage were proceeded. The consequence of the experiments indicated that the residual voltage ratio decreased first and then increased. The zinc oxide varistor samples showed good properties with the composition of zero point four five mole fraction gallium and zero point zero three mole fraction indium. Showing a residual voltage ratio of one point five four, a nonlinear coefficient of sixty five, and a voltage gradient of four hundred and forty one volt per millimeter. Applying the high performance ZnO varistors to surge arresters will decrease the overvoltage level from 1.6-1.7p.u. to 1.2-1.3p.u., to realize the target to deeply suppress the switching overvoltage. This will further reduce the insulation level and manufacturing bottleneck of UHV power apparatus. This study is of great significance to promote the protective effect of the equipment assembled by zinc oxide varistor and the stabilization of the power system.