Disconnector is an accessory of surge arrester, connected in series with arrester. When arrester in fault, the power frequency current flow will make the resistor inside the disconnector heat up and operate, then the fault arrester will be disconnected from the power system, and cut the grounding short circuit fault current, preventing the further expansion of the fault, and gives the fault arrester with visibility disconnecting mark, so that maintenance personnel can find the fault point easily and replacement in time.