Three steps lightning and surge protection for power systems

1. Why power system need three step lightning surge protection?
First step lightning protection purposes: to prevent the surge voltage transmission directly from LPZ0 into LPZ1, the tens of thousands to hundreds of thousands of volts of surge voltage to 2500 ~ 3000V
Second step surge protection purpose: to mine through the first level of residual surge voltage to 1500V ~ 2000V, on the implementation of LPZ1 ~ LPZ2 equipotential connection.
Third step lightning surge protection purpose: the ultimate means of protection equipment will reduce the value of the residual surge voltage to less than 1500V, the surge of energy not to damage the device.

2. How to determine whether power supply system should be carried out three steps lightning surge protection?
It should be determined based on the pressure level of equipment to be protected, if only twos steps surge protection can be done to limit the voltage of equipment to be protected, it only needs to do two steps lightning and surge protection; if the residual voltage of equipment to be protected is very low, maybe it needs four step lightning and protection or more steps.
Because the energy needs of three progressively lightning discharge, the transmission line will be sensitive LEMP, with information systems for buildings, three mine is a lower cost, more adequate protection of choice.

3. Which is the maximum and minimum distance between the surge arresters(surge protection device, SPD)and the protected equipment, and between two different surge protectors?
The distance with between the surge arresters and the equipment to be protected should be as close as possible, and within 10m. The distance between Class II surge arresters (switching type SPD) and Class III surge protectors (voltage limiting type SPD) should be no less than 10m; the distance between Class III surge protection devices (voltage limiting type SPD) should be no less than 5m.