Zinc Oxide Surge Arresters is the most advanced preventer against over-voltage in the world. Since ZOSA resistors are made up of zinc oxide films. Zinc Oxide Surge Arresters has a good voltage-ampere characteristics as compared with SiC arresters, it’s over-voltage and current flow are in creased greatly and resulted the essential changes of ZOSA characteristics.The microns ampere degree current flows only while ZOSA is operating under normal voltage, but the amount of current will be thousands am-peres when ZOSA withstand over-voltage, because of ZOSA has a good ! non-linear characterizatios. At that time it is in case of throughway state relief over-voltage energy, so that limit effectively the damage to the equiplments of transmit and transformation.