What is the function and principle of surge protector?

Surge refers to the peak value that exceeds the stable value instantaneously, including surge voltage and surge current.
The surge in the power supply system mainly comes from two reasons: external (cause of lightning) and internal (start and stop of electrical equipment and failure, etc.). Surge is often characterized by a very short time (overvoltage caused by lightning is often in microseconds, and overvoltage caused by electrical equipment is often in milliseconds), but the instantaneous voltage and current are extremely large, which is very likely to affect electrical equipment and electrical equipment. Cables are a hazard, so surge protectors are needed to protect them.

Surge protector is an electronic device that provides safety protection for various electronic equipment, instruments, and communication lines. It is mainly used to limit overvoltage and discharge surge current. The surge protector is generally connected in parallel with the protected equipment. When overvoltage occurs, it can play the effect of shunt and voltage limiting. Prevent excessive current and voltage from causing damage to the equipment.
The core component of the surge protector is an internal nonlinear component. According to the different nonlinear components, surge protectors can be divided into switching type (the core component is mainly discharge gap) and voltage limiting type (the core component is mainly varistor).

Although the working principles of the discharge gap and the varistor are different, the basic characteristics are very similar: when there is no overvoltage, their impedance is very high, usually megohm level, almost equivalent to an open circuit. When an overvoltage occurs, the impedance drops rapidly to a few ohms, and the surge current flows into the ground through the surge protector without entering the device. At the same time, because the impedance of the surge protector is very small at this time, its two The pervasive voltage is also relatively small, and because it is connected in parallel with the protected equipment, it prevents the equipment from being subjected to large surge voltages. In this way, it has the effect of leakage and pressure limiting.