Choose The Appropriate Surge Protector According To The Power Supply System

To ensure the safety of buildings and electronic information systems and prevent lightning strikes, many locations require lightning protection devices (SPDs). However, different locations require different types of surge protective device. When selecting a SPD, what should be considered?

Confirming the Power Supply System
First, we should determine our power distribution system, whether it's TT, TN, or IT. Only after determining the distribution system can we select the surge protector protection mode and wiring configuration, and thus the appropriate surge protection device.

For example, TN-C uses a 3P SPD, TN-S uses a 4P SPD, and TT uses a 3P+N SPD.

Selecting the Maximum Discharge Current (Imax)

The peak current of the 8/20 μs current wave flowing through the SPD is used for Class II classification testing. Imax and In have many similarities; both use the peak current of the 8/20 μs current wave for Class II classification testing. However, the difference is also obvious: Imax only tests the SPD once, without substantial damage; whereas In can be tested 20 times without substantial damage. Therefore, Imax is the current limit of the impact, so the maximum discharge current is also called the limiting impact current capacity. Obviously, Imax>In.