What is a surge protection device and how does it work?

What is a Surge Protection Device (SPD)?

A surge protection device (also called 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 must protect, but 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.

How does a surge protection device (SPD) work?

1. In normal situations (no surge)
- The SPD is in high impedance mode and does nothing.
- The electrical current flows directly to the installation and equipment.
2. In the event of a voltage spike (e.g., lightning, switching spike, etc.)
- The SPD detects that the voltage exceeds its threshold (clamping voltage).
-  It switches to low impedance at lightning speed.
- The excess energy is diverted to earth or back to the source, instead of continuing to the equipment.
- Once the surge is over, the SPD returns to high impedance.

This prevents voltage surges from damaging sensitive electronics such as PLCs, IT equipment, security systems, and HVAC controls.

What types of surge protectors are there?

SPD is designed to limit transient overvoltage (coming from atmospheric origin or switching surges due to network operations) and evacuate the peak voltage to earth, to limit the amplitude of this overvoltage to a value that is not hazardous for the electrical installation.
Today, standards define three types of SPD for low voltage electrical installations: Type 1, Type 2 & Type 3 SPDs.
Depending on the environment and on the current and voltage waves, you might use some of those types.

•    Type 1 SPD, such as our range Acti9 iPRD1, PRD1

•    Type 2 SPD, such as our ranges Acti9 iQuick-PF, iQuick-PRD or Acti9 iPRD

•    Type 3 SPD, such as our range Acti9 iPRD

Released for: Schneider Electric Belgium