The ZGG40-275 Modular Power Supply SPD can be used for protection of L-N and L/N-PE. It is applied in the low voltage AC power distribution system, and connected between AC power supply and system equipment in parallel. It can prevent equipment from the impulse surge and transient overvoltage caused by the outside environment (such as lightning, EMI, etc.) or by the system (such as switching effects of the system, startup or shutoff of the inductance and capacitance load, etc.).