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 is designed to limit transient overvoltages of atmospheric origin and divert current waves to earth, so as to limit the amplitude of this overvoltage to a value that is not hazardous for the electrical installation and electric switchgear and controlgear.
SPD eliminates overvoltages
- in common mode, between phase and neutral or earth;
- in differential mode, between phase and neutral.
In the event of an overvoltage exceeding the operating threshold, the SPD
- conducts the energy to earth, in common mode;
- distributes the energy to the other live conductors, in differential mode.