What is the P-number of surge protectors

A surge protector is a device used to protect electrical equipment from lightning or other transient overvoltage effects. It can limit excessive voltage to a safe range and guide excess current into the ground wire, thereby avoiding equipment damage. The P-number of surge protector refers to its protection mode, which means it can provide protection between which lines. Different P numbers are suitable for different power systems and wiring methods.

Generally speaking, there are several P-numbers for CHYT surge protectors:

1P: indicates that there is only one protection module, usually used in single-phase TT systems, and the protection mode is L-PE, which is the protection of live wire to ground.

1P+N: Refers to two protection modules, namely the voltage sensitive module for the live line to zero line and the discharge tube module for the zero line to ground line. They are usually used in single-phase TT or TN-S systems, and the protection modes are L-N and N-PE, that is, the protection of the live line to zero line and the zero line to ground.

2P: Refers to having two protection modules, usually used in single-phase TN or IT systems, with protection modes of L-PE and N-PE, that is, protection for live wire to ground and neutral wire to ground.

3P: Refers to three protection modules, usually used in three-phase TN-C or IT systems. The protection modes are L1-PE, L2-PE, and L3-PE, which respectively protect the three-phase live wire against ground.

3P+N: Refers to four protection modules, namely the voltage sensitive module for three-phase live wire to neutral and the discharge tube module for neutral wire to ground. They are usually used in three-phase TN-S or TT systems, and the protection modes are L1-N, L2-N, L3-N, and N-PE, that is, the protection of three-phase live wire to neutral and neutral wire to ground.

4P: Refers to four protection modules, usually used in three-phase TN-S or TT systems. The protection modes are L1-PE, L2-PE, L3-PE, and N-PE, which are full mode protection for three-phase live wire to ground and neutral wire to ground.

When selecting the P-number of surge protectors, comprehensive consideration should be given to factors such as the actual power system type, grounding method, and distribution method. Generally speaking, surge protectors that can provide full mode protection should be selected as much as possible to improve the lightning protection effect. At the same time, the requirements for the selection, installation, and coordination of surge protectors in the national standards GB 50057 "Code for Design of Lightning Protection of Buildings" and GB 50343 "Technical Code for Lightning Protection of Building Electronic Information Systems" should be followed.

Here are some examples of application scenarios for CHYT surge protector P-numbers:

In a single-phase 220V TT system, users need to install a first level surge protector at the main distribution box, a second level surge protector at the branch distribution box, and a third level surge protector at the equipment end. So users can choose 1P+N type primary surge protector, 2P type secondary surge protector, and 1P+N type tertiary surge protector.

In a three-phase 380V TN-S system, users need to install a first level surge protector at the main distribution box, a second level surge protector at the branch distribution box, and a third level surge protector at the equipment end. So users can choose the first level surge protector of 4P or 3P+N type, the second level surge protector of 4P or 3P+N type, and the third level surge protector of 4P or 3P+N.

In a three-phase 380V TN-C system, users need to install a first level surge protector at the main distribution box, a second level surge protector at the branch distribution box, and a third level surge protector at the equipment end. So users can choose the 3P type primary surge protector 9, the 3P type secondary surge protector 10, and the 3P type tertiary surge protector.