A surge protective device (Surge Protective Device, abbreviated as SPD), also known as a lightning surge protector or a lightning arrester, is an indispensable overvoltage protection device in modern electrical systems. It can quickly conduct and discharge the surge current in the instant when lightning induction, line operation or static electricity generate instantaneous high voltage, thereby clamping the line voltage within a safe range. This effectively protects distribution cabinets, distribution boxes, precision instruments, household appliances and various weak electrical equipment from breakdown, burning or malfunction damage.