The first stage is installed on the low-voltage side of the household power transformer. The surge protector should be a three-phase voltage switching power supply lightning arrester, and its lightning flux should not be less than 60KA. This level of power supply lightning arrester should be a large-capacity power supply lightning arrester connected between each phase of the entrance line of the user's power supply system and the earth.
The second stage is installed at the line output of the distribution cabinet. The surge protector should be a voltage-limiting power supply lightning arrester. Its lightning current capacity should not be less than 20KA and should be installed at an important location. Or branch distribution points that supply power to sensitive electrical equipment. These power surge arresters can better absorb the remaining surge energy that has passed through the surge arrester at the user's power supply entrance, and have an excellent suppression effect on transient overvoltage.
The third level is installed at the AC power incoming end of electronic information equipment. The power supply lightning arrester should be a series voltage-limiting power supply lightning arrester, and its lightning current capacity should not be less than 10KA.
The last line of defense can be to use a built-in power lightning arrester in the internal power supply of the electrical equipment to completely eliminate tiny transient overvoltages.
Extended information
Surge protectors can be divided into voltage switching type, voltage limiting type and combination type.
⑴Voltage switching SPD. It presents a high impedance when there is no instantaneous overvoltage. Once it responds to a lightning instantaneous overvoltage, its impedance mutates to a low impedance, allowing lightning current to pass through. It is also called a "short-circuit switch type SPD".
⑵Pressure-limiting SPD. When there is no instantaneous overvoltage, it has high impedance, but as the surge current and voltage increase, its impedance will continue to decrease, and its current and voltage characteristics are strongly nonlinear, sometimes called "clamp-type SPD".
⑶ Combined SPD. It is composed of a voltage switching type component and a voltage limiting type component. It can display characteristics of voltage switching type, voltage limiting type or both, depending on the characteristics of the applied voltage.
Baidu Encyclopedia-Surge Protector