What is surge protection device

 Surge Protection Devices (SPD) are used for electric power supply networks, telephone networks, and communication and automatic control buses.

    The Surge Protection Device (SPD) is a component of the electrical installation protection system.

    This device is connected in parallel on the power supply circuit of the loads that it has to protect. It can also be used at all levels of the power supply network.

    This is the most commonly used and most efficient type of overvoltage protection.
    SPD connected in parallel has a high impedance. Once the transient overvoltage appears in the system, the impedance of the device decreases so surge current is driven through the SPD, bypassing the sensitive equipment.