Should The Surge Protector Installed In The Distribution Box On The Roof Be Primary Or Secondary?

In a subsystem on the roof of an industrial plant, a surge protector needs to be installed in the incoming control cabinet of this subsystem. Within the protection range of the lightning rod, should the surge protective device installed in the distribution box on the roof be of level one or level two? If level I is selected, how to determine the value of Iimp? If level II surge protector is selected, what is the value of In kA?

Article 3 of Section 5.4.3 of the national standard GB 50343-2012 stipulates: For AC power supply lines entering a building, at the junction of LPZ0A or LPZ0B and LPZ1 areas such as the main distribution box of the line, a surge protector of type I test or a surge protector of type II test should be installed as the first level of protection;

The national standard stipulates that for buildings with different protection levels, the flow rate of the selected surge protector can be different. Therefore, the specific selection of the surge protector first requires the determination of the lightning protection level of the building.

National Standard GB 50343-2012 Section 4.3.1: Building electronic information systems can be classified according to Table 1-1 based on their importance, economy and value.

Should the distribution box on the roof use a level 1 or level 2 surge protection device? Buildings with other protection levels are analogous to the requirements in the table's graded protection standards. At present, the common Iimp value of a level 1 surge protector is 25kA, which is not much different from the cost of a 15kA level 1 surge protector. Therefore, considering the safety of the equipment, it is recommended that you choose a level 1 surge protector with a larger flow rate, which not only has a long service life, but also more effective lightning protection.