Surge Protective Devices（Direct Current SPD ）

Scope of Application

SPD is suitable for all kinds of low-voltage distribution systems with grid voltage below 1000 volts and frequency of 50/60HZ, such as post and telecommunications, railways, financial systems, oil fields, high-rise buildings, houses and office buildings. To protect the electrical appliances (such as computers, instruments and equipment, household appliances, etc.) of these power users from lightning strikes, transient overvoltage and other surge overvoltage damage. Ensure equipment and personal safety. It is an ideal overvoltage protection device.

Main structure and working principle

In the three-phase four-wire system, protectors are connected between the three phase wires and a neutral wire to the ground wire (see the figure below). Under normal circumstances, the protector is in Levin state, and when the power grid is subjected to surge overvoltage due to lightning or other reasons. The protector will be quickly turned on in nanosecond time, introducing surge overvoltage into the earth, thus protecting the electrical equipment on the power grid. When the surge overvoltage passes through the protector and disappears, the protector returns to the high resistance state again. So as not to affect the normal operation of the power grid.

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