How To Choose Surge Protector Parameters - Very Important
As electrical practitioners, we often encounter a problem at work: How to choose the parameters of the surge protector? How large should it be? Today, the editor will talk to you about the selection of surge protection device parameters in terms of the energy coordination of the surge protective device on the line.
Selection of surge protector parameters On the line, the surge protector is designed and installed based on the principle of step-by-step discharge. For the first-level surge protector, its main function is to discharge current, which needs to discharge about 80% of the lightning current. Therefore, when selecting a level 1 surge protector, we focus on its maximum impact current parameter. The national standard requires a minimum of 12.5KA (10/350us). Of course, it is also necessary to select a higher level of current parameters according to the importance of the building.
Selection of surge protector parameters For the second-level surge protector, its main function is called voltage limiting. Their ultimate function is to limit the voltage of the lightning current to the range that the equipment can tolerate, that is, the protection voltage level Up of the second-level surge protector must meet the withstand voltage requirements of the protection equipment and will not cause damage to the electrical equipment.
Therefore, for the second-level surge protector, we focus on its UP value. Under normal circumstances, if the Up value of the surge protector + the sum of the resistance and inductance voltage drop on the line △U < 0.8 times the device's impulse withstand voltage, then we can say that this is a qualified surge protector, and the two-level surge protectors also perfectly achieve capacity coordination.
The selection of surge protector parameters is sometimes due to the long line, and there will be a distance between the SPD and the equipment, so the lightning current may be excited in the line, resulting in a reflected wave effect. In the actual design of the scheme, the maximum oscillation distance and the maximum coupling distance should also be considered to determine how many surge protectors to install.
