In a three-phase four-wire system, protectors are connected between the three phase lines and one neutral line and the ground. Under normal circumstances, the protector is in a high-resistance state. When the power grid deals with surge overvoltage due to lightning strikes or other reasons, the surge protector will immediately conduct rapidly within nanoseconds, introducing the surge overvoltage to the ground, thereby protecting the electrical equipment on the power grid. When the surge voltage passes through the protector and disappears, the protector returns to a high-resistance state, thus not affecting the normal operation of the power grid.

Lightning protection modules (surge protectors) are mainly applicable in gas lines with a (50HZ or 60Hz) impulse current capacity not exceeding (200KA). They limit the amplitude of transient overvoltage, absorb, consume or discharge the energy of surge current, and are suitable for use in situations with high overvoltage categories. It can convert the protected electrical components from one overvoltage category to a lower one, and is suitable for household and similar place electrical appliances.