What is Surge Protection : Working, Types and Its Applications

All the electronic equipment, devices, and gadgets are helping us to do our daily works very comfortably. Day by day the electronic devices are available in the market at different prices. Here one of the reasons for the price difference is durability and how long the device works properly. This mainly depends on how the internal circuit of the device can capable to handle the voltage fluctuations. If the device gets the fluctuations in the input voltage then it leads to the damage of the device because the fluctuations in the supply voltage may harmful to the device. Here in this article, we are going to know what is surge protection, definition, function, and applications.

What is Surge Protection?

Definition: The surge current may occur because of voltage imbalances, radio interferences, interferences in transformers and differences in potential. Surge can be defined as, it is a sudden change in the voltage, current or power in a circuit. Generally, the standard voltage level which is supplied to homes from power stations is varied from one country to another country. In India, the standard voltage level is 220V-230V and in the USA the value is 120V. Because of a few problems, the supply voltage may suddenly increase beyond its standard value. The surge protector also called a surge suppressor.

  • If the voltage suddenly increases lasts for 3 or more nanoseconds, that is called as “surge”
  • When the sudden voltage lasts for one or two seconds, then it is called as “spike”

Surge Protection Device Working

The importance of surge protection devices (SPD) is to prevent voltage spikes and surges. This device must perform two tasks for protecting electronic devices. They are

  • It should limit the surge voltage in terms of amplitude. So, the electric devices won’t exceed the voltage.
  • It should discharge the surge voltage to the ground without causing any damage to the devices.

The need for this device or surge suppressor is to prevent sudden changes in AC voltage than the standard voltage level. To avoid the surge effect surge protection devices are useful. These devices forward the voltage from ports to the devices through power lines. If the surge occurs this surge suppressor device passes the extra voltage to the grounding wire.

Surge Protection Device Function

The surge protection device has three basic components like voltage sensor, controller and latches/unlatch circuit. The voltage sensor observes the line voltage and the controller reads the voltage level and decides whether it is maintaining the standard voltage level or not. If there are any differences then it can be solved by the latch/unlatch circuit. There is another type of surge protector that has built-in electronic devices for their safety.

These are widely used in electronic devices to prevent the damages that occurred due to surge. In switch mode power supply devices, these types of devices are used. The above surge protection device is a widely used device in the switch mode power supply. There are three surge protector lines in the surge protection device. Surge protector 1 across AC Line 1 and AC Line 2 is called differential mode surge suppression. Surge protector 2 and surge protector 3 are called common mode surge protection.


Differential mode surge protection is established between two wires. This differential surge protection part clamps any voltage spikes between AC lines 1 and 2. And surge protector2 and surge protector 3 both are clamps the voltage transitions on the hot wire to ground. Surge protector 1 from this device prevents the voltage spikes and in case of heavy voltage spikes, surge protector 2 and surge protector 3 is useful.

Circuit Diagram

The below figure indicates the surge protection device circuit diagram. This device passes the electrical current from the ports to the electronic devices. If any spikes or surge voltage occurs those can be forwarded to ground lines with help of MOV. It is a component in SPD’s plays an important role while forwarding the surge voltage to the ground wire. MOV is known as Metal Oxide Varistor.

surge-protection-device circuit-diagram

It’s the connection between the hot power line and the ground wireline. G1 and G2 are the gas discharge tubes. From the above-simplified surge protection device circuit diagram, common-mode surge voltage appears between L-PE and N-PE. And these can be limited by M1-G1 and M2-G2 and G1-G2. Differential surge voltage appeared between L-N and it is limited by M1-M2.

Different Types

These devices are classified into two different types based on the connection and type of voltage. In those two types, one type of SPD is connected between the active conductors. And another type of SPD is connected between conductor and protective conductor.


The two different surge protection devices diagrams are shown below. This one also indicates the surge protection device connection diagram.


Surge Protector Rating

This detailed description will indicate the complete characteristics and limitations of the surge protection device. And also this rating indicates how much of surge voltage can SPD handles and how much of surge voltage can forward to ground etc.

Clamping Voltage

This feature indicates at what voltage the MOV’s can conduct the electricity to ground. If the clamping voltage level is 300V means, it can prevent and save the device up to this level. And if the input voltage level to this SPD device is more than this 300V, this particular SPD won’t work. So, higher clamping voltage is always best for the surge protection devices.

Energy Absorption

This value is given in the form of joules. And this value indicates, how much energy can absorb by this SPD device.

Indicator Light

This light helps to find out whether all components of the device is working or not. By this glow of the light, we can estimate the working condition of the surge protection device.

Surge Protection Device Applications

  • Every year there are many electronic devices are going to be damaged due to transient voltages. So this should be avoided by the surge protection devices.
  • These are used in the electrical installation systems as protection to them. They going to prevent the surges.
  • Used in lighting application systems and distribution boards.
  • These devices are very helpful in data applications. Like protecting the equipment which is connected to the data lines.
  • Has wide applications and importance in product-based companies.
  • In all electronic devices for larger durability.
  • Especially useful for very low voltage devices that are operated between the 3-48V range.

Thus, this is all about an overview of the surge protection device. Here, voltage surges and spikes can be caused due to interference of radio waves, interference in the transformer & some natural reasons. These surges always be a reason for the damaging of the electronic devices and sometimes these surges can lead to big losses. So to overcome and prevent purpose, these devices are introduced. Based on the voltage connection, surge protection devices are categorized into two types. These devices handle the large surge voltages by using various techniques.