Lightning protection devices are connected in series and parallel according to different models and functions:
Surge protector access mode: In the TN standard, in general, the surge protector only needs to be used in a common mode connection method, that is, it is connected between the phase neutral line and the protective ground line. However, at the starting position of the TN-S standard, there is no need to connect the surge protector between the neutral line and the protective ground line. Only differential mode connection is required for power ports of particularly important equipment at the third, fourth and B lightning protection levels in Class A lightning protection levels, that is, to add surge protectors connected between the phase line and the neutral line.
In the TT standard, when the first stage surge protector is located behind the leakage protector, the above common mode connection method can be performed. When the first-stage surge protector is located in front of the leakage protector and the high-voltage system is the center point grounding system, the surge protector should be connected with a "3+1" method, that is, three phase lines connect one surge protector to each of the neutral lines, and one surge protector to the protective ground line. In the IT standard, the surge protector is only used for common mode connection.
