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Difference between surge protector 4P and 3P+N

September 26,2023

4P surge protector refers to the common connection of four independent surge protectors.


In the field of low-voltage lightning protection, there is usually another   surge protector  named 4+0 structure for this type of structure.

3PN surge protector refers to the zero connection of three independent surge protectors, and then through another surge protector to achieve the protection structure between zero ground, in the field of low-voltage surge protection, this type of surge protector is called  3PN structure surge protector, or 3+1 structure surge protector.

For these two types of surge protectors, there are similarities and differences, mainly in the following aspects:


1, 3PN (3+1) structure surge protector and 4P (4+0) structure surge protector in the protection of the phase line, most of the use of voltage limiting components as the core, mostly for the pressure sensitive resistor, there are also manufacturers use switch type components as the core, such as graphite gap;

2, 3PN surge protector and 4P surge protector appearance size is basically the same;

3. In terms of parameters, the key parameters of the phase line are basically consistent.

(2)The difference:

1, the internal structure principle is different

The three phase lines of the 3PN surge protector are connected to zero, and the three phase lines of the 4P surge protector are connected to the zero line together.

2. Different protection modes.

The surge protector of 3PN structure is full mode protection, in which the differential mode protection (L-N) is between the three phase lines and the neutral line, and the common mode protection (N-PE) is between the zero ground. The three phase lines and neutral lines of the 4P structure surge protector are all common mode protection (L-PE, N-PE).

(3)the internal N-PE protection between the use of different components.

The 3PN surge protector uses discharge tube or multi-layer combined discharge gap and other switching components between N-PE, while the protection between N-PE with 4P structure SPD uses varistor, a voltage limiting component.


(4) Different application scenarios.

The 3PN structure surge protector is suitable for TN-S, TT power supply system, TN power supply system and IT power supply system of the lead line. The 4P surge protector can only be used in the TN-S power supply system, the TT system (installed behind the TT system residual current protector) and the IT power supply system that does not lead to the middle line (actually only used 3P).

(5)Different backup protectors are matched.

The GB50057-2010 standard stipulates that the 3PN structure surge protector only needs to match the 3P special backup protector, and the 4P structure surge protector must match the 4P special backup protector.

(6) Security.

SPD of 3PN structure Because the N-PE is a switching component, it is isolated and off. When the surge protector between L-N and PE deteriorates, the voltage to ground of the device does not increase, thus avoiding electric shock accidents caused by SPD deterioration and failure.

Because there is no isolation effect between N-PE and 4P SPD, when a certain SPD phase deteriorates, if the device is improperly grounded, an electric shock accident may occur.

In addition, because in the same transformer power supply range, the PE line in the TN-S system is mostly connected, when a phase surge failure, it will cause the grounding fault, the fault voltage will be transmitted along the PE line to other equipment, thus threatening the safety and stability of other equipment in the same transformer power supply range, if the equal potential connection of a device in the system is poor, Equipment damage will occur.

In the actual project application, it is very important to choose the right SPD, careless selection will cause lightning protection safety risks, first consider the power supply system, and then the voltage level and protection level (through flow and limit voltage level). At the time of purchase, it is best to provide us with drawings and relevant information in order to provide you with the correct selection. WPX is a manufacturer specializing in the production and development of lightning arrester. WPX box signal lightning arrester includes: network signal lightning arrester, control signal lightning arrester, limited TV signal lightning arrester, POE signal lightning arrester, antenna feed signal lightning arrester.telephone signal lightning arrester, video signal lightning arrester, etc., can provide users with three-pole protection from B to F. Users can choose the signal lightning arrester according to the specific parameters of the system equipment, and our company can also provide customized services for users to create a signal lightning arrester exclusive to you.

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