Second level of protection
The purpose is to further limit the value of the residual surge voltage through the first level of lightning protection to 1500-2000V, the LPZ1-LPZ2 implementation of the equipotential connection.
Sub-distribution cabinet line output power supply lightning arrester as the second level of protection should be voltage limiting power supply lightning arrester, its lightning current capacity should not be less than 20KA, should be installed in the power supply to important or sensitive power equipment at the branch distribution. These power supply lightning protector for the user through the power supply entrance surge discharger residual surge energy for better absorption, for transient overvoltage has an excellent suppression effect. The use of the power supply lightning arrester requires the maximum impact capacity of 45kA per phase or more, the required limit voltage should be less than 1200V, called CLASS Ⅱ power supply lightning arrester. General users of the power supply system to achieve the second level of protection can reach the requirements of the operation of power-using equipment
The second level of power supply lightning protector using Class C protector for phase - in, phase - ground and in - ground full mode protection, the main technical parameters are: lightning through-current capacity greater than or equal to 40KA (8/20μs); residual voltage peak is not greater than 1000V; response time is not greater than 25ns.
The third level of protection
The purpose is the ultimate means of protecting equipment, the value of the residual surge voltage is reduced to within 1000V, so that the energy of the surge does not damage the equipment.
In the electronic information equipment AC power inlet end of the power supply lightning protector installed as the third level of protection should be series-limited power supply lightning protector, its lightning through-current capacity should not be less than 10KA.
The last line of protection can be used in the internal power supply part of the power equipment with a built-in power supply lightning arrester, in order to completely eliminate the purpose of the small transient overvoltage. The power supply lightning arrester used there requires a maximum impact capacity of 20KA per phase or less, the required limiting voltage should be less than 1000V. For some particularly important or sensitive electronic equipment with the third level of protection is necessary, but also to protect power-using equipment from the transient overvoltage generated within the system.
For microwave communication equipment, mobile station communication equipment and radar equipment, such as the use of rectifier power supply, depending on its working voltage protection needs are appropriate to choose the working voltage of the appropriate DC power lightning arrester as the last level of protection.
Fourth level and above
According to the voltage level of the protected equipment, if two levels of lightning protection can be done to limit the voltage below the level of the equipment, only two levels of protection are required, if the level of voltage resistance of the equipment is low, it may require four or more levels of protection. The fourth level of protection whose lightning through-current capacity should not be less than 5KA. [3]