Surge Protectors Are Classified According To Their Working Principles

According to its working principle, SPD can be divided into voltage switching type, voltage limiting type and combination type.
⑴ Voltage switching type SPD. It presents high impedance when there is no transient overvoltage. Once it responds to lightning transient overvoltage, its impedance suddenly changes to low impedance, allowing lightning current to pass through. It is also called "short-circuit switch type SPD".
⑵ Voltage limiting type SPD. When there is no transient overvoltage, it is high impedance, but with the increase of surge current and voltage, its impedance will continue to decrease. Its current-voltage characteristics are strongly nonlinear, sometimes called "clamp type SPD".
⑶ Combination type SPD. It is composed of voltage switching type components and voltage limiting type components. It can show the characteristics of voltage switching type or voltage limiting type or both, which depends on the characteristics of the applied voltage.