Surge Protectors Are Classified By Purpose

According to their use, Surge Protectors can be divided into two types: power line SPDs and signal line SPDs.

(1) Power line SPD

Since the energy of lightning strikes is very huge, it is necessary to gradually discharge the lightning energy to the ground through a graded discharge method. In the non-lightning protection zone (LPZ0A) or at the junction of the direct lightning protection zone (LPZ0B) and the first protection zone (LPZ1), a surge protector or a voltage-limiting surge protector that has passed the Class I classification test is installed as the first-level protection to discharge the direct lightning current, or when the power transmission line is directly struck by lightning, the huge energy conducted is discharged. At the junction of each sub-zone (including the LPZ1 zone) after the first protection zone, a voltage-limiting surge protector is installed as a second, third or higher level protection. The second-level protector is a protective device for the residual voltage of the previous level protector and the induced lightning strike in the zone. When a large amount of lightning energy is absorbed in the previous level, a part of the energy that is quite huge for the equipment or the third-level protector will be transmitted and needs to be further absorbed by the second-level protector. At the same time, the transmission line passing through the first-level lightning arrester will also induce lightning electromagnetic pulse radiation. When the line is long enough, the energy of the induced lightning becomes large enough, and the second-level protector is required to further discharge the lightning energy. The third-level protector protects the residual lightning energy passing through the second-level protector. According to the withstand voltage level of the protected equipment, if the two-level lightning protection can limit the voltage to be lower than the withstand voltage level of the equipment, only two levels of protection are required; if the withstand voltage level of the equipment is low, four or even more levels of protection may be required.

(2) Signal line SPD