What Is Common Mode Protection And Differential Mode Protection Of Surge Protector?

6.1.1 of GB/T 18802.12-2014: SPDs located at or near the starting point of the surge protection device should be connected at least between the following points:

a) If there is a direct connection between the neutral line and PE at or near the starting point of the surge protector, or there is no neutral line; between each phase line and the main grounding terminal or between protective conductors, the shorter connection line is preferred;

b) If there is no direct connection between the neutral line and PE at or near the starting point of the surge protective device:

Connection type 1 (CT1) - between each phase line and the main grounding terminal or between protective conductors (L-PE), between the neutral line and the main grounding terminal or between protective conductors (N-PE), the shorter connection line is preferred.