What is Surge Protection Device and How it Works?

Surge Protective Devices (SPDs), also known as surge suppressors or surge arresters, the main function of a surge protective device is to divert excess voltage and current away from the equipment being protected, thereby limiting the voltage level.

These surges can occur due to lightning strikes, grid switching, electrical faults or other reasons and can damage sensitive electronics and equipment.

How do surge protectors work?

1. Voltage monitoring

A surge protection device continuously monitors the voltage level of the electrical system to which it is connected.

Surge protection devices kick in when the voltage rises above a certain threshold (indicating a surge or transient event).

2. Inrush current shunt

Surge protectors provide a low impedance path for surge current to flow.

Surge protectors typically consist of metal oxide varistors (MOVs), gas discharge tubes (GDTs), or other components with fast response times and high surge handling capabilities.

3. Metal Oxide Varistor (MOV)

MOVs are the most commonly used components in surge protection devices.

Metal oxide varistors have a nonlinear voltage-current characteristic, meaning that their resistance decreases as the voltage across them increases.

When a surge occurs, the MOV quickly diverts excess current away from the protected equipment, effectively clamping the voltage to a safe level.

4. Gas discharge tube (GDT)

GDTs are another element used in surge protection devices.

A gas discharge tube contains a gas-filled chamber where ionization occurs when the voltage exceeds a certain level. This ionization creates a low-resistance path for the surge current, diverting it away from the device.

5. Absorption and dissipation

Once the surge current is diverted, the surge protection device absorbs the excess energy and dissipates it as heat. This prevents energy from reaching connected devices and causing damage.

6. Reset or replace

In the event of a severe surge or multiple surges, the surge protection device may reach its maximum capacity and be permanently damaged. In this case, the surge protection device can be replaced or manually reset, depending on its design.

Where is the surge protection installed?

Surge protection devices are typically installed at the main electrical service entrance to protect the entire power system, or at specific points of use to protect individual units or equipment.