With the realization of intelligent and networked low-voltage distribution system, a large number of electrical equipment with electronic components is used in the distribution system, which is extremely vulnerable to transient overvoltage in the system.

Transient overvoltage can also be called “surge”, it is caused by lightning discharge, electrical system operation, or electrostatic discharge. It enters the low power distribution system through the coupling of current, inductance, capacitance, etc., and makes a momentary current and voltage fluctuation in the system, among which the transient overvoltage caused by lightning discharge is the most harmful.

According to statistics, the number of lightning discharge on the earth up to 100 times /s, in the 1.5-2.0 km range of power lines and communication signal lines as the center of the lightning strike, the transient overvoltage is high enough to cause interference or even damage to the electrical equipment connected to these lines. All kinds of surge protectors and related overvoltage protection came into being.

Surge protectors generally referred to as SPD. By studying the mechanism of lightning discharge, various kinds of surge protectors for low-voltage distribution system and telecommunication signal network have been developed to effectively protect the system. There are complete lightning protection schemes for building power distribution systems and industrial power distribution systems, and generally Type 2 and Type 3 SPD are used.