The Ultimate Guide to Surge Protection Device

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Electricity has always been an invention that is renowned for making tasks of daily living easier, as well as being an invention that also possesses life-threatening risks, which is why every electrical system is composed of various components to both regulate and safeguard the electrical flows.

Surge Protection Devices are a device that safeguards the electrical system from man-made or natural errors. 

Now, if anyone is new to the topic of Surge Protection devices, here is a detailed topic on them and other necessary facts that one should know.

What Is a Surge Protection Device? 

Surge protection devices, or in short form, SPDs, are special and important electronic devices that are used to protect the electrical installation, which consists of the consumer unit, wiring from electrical power surges which is referred to as transient overvoltages.

Electric flow is not constant. There are times when minor hindrances might occur and cause a splurge of electric power surges which might cause temporary, permanent, or even worse damage to the electrical system. To avoid such instances, Surge protection devices are mounted in every household and industry electrical system.

Additionally, sensitive electronic devices such as laptops, televisions, washing machines, and safety circuits like fire detection systems and emergency lighting are protected by SPDs when they are connected to the installation. Transient overvoltages have the potential to harm equipment with delicate electronic circuitry.

What Are Transient Overvoltages?

Transient overvoltage consequence
Source: Unsplash

Transient overvoltages are short-lived electrical surges caused by the unexpected release of previously stored or artificially produced energy. There are two types of transient overvoltages: natural and man-made.

How Do Transient Overvoltages Occur?

Man-made transients are caused by the switching of motors and transformers, as well as certain types of lighting. Previously, this has not been an issue in household installations. Still, with the introduction of new technologies such as electric vehicle charging, air/ground source heat pumps, and speed-controlled washing machines, installations are changing, making transients far more likely to occur.

Most frequently, natural transient overvoltages result from direct lightning strikes on nearby overhead power or phone lines, which causes the transient overvoltage to move along the lines and inflict serious damage to the electrical installation and related equipment.

The damages caused by transient overvoltages are classified into disruptions, degradation, damage and downtime.

  • Disruptions produce little physical damage but disrupt electronic systems, causing data loss, software corruption, system crashes/lock-ups, and spurious tripping.
  • Degradation is the progressive deterioration of components caused by long-term lower-level transient overvoltages, which reduces component life and makes them susceptible to early failure.
  • Damage appears as burnt-out circuit boards as a result of overheating, insulation failure, and the consequent power aftereffects. Damage may also result from improper operation or a short circuit brought on by a transient overvoltage.
  • Downtime is any interruption to work or activities that results in lost revenue and higher expenses.

According to the most recent version of the IET Wiring Regulations, BS 7671:2018, protection against transient overvoltage must be provided in situations where overvoltage could result in:

  • cause great harm to or the death of a person.
  • Either cause a disruption of public services or harm to cultural heritage.
  • Cause a halt to business or industrial activity.
  • Impact a large number of people who are nearby.

How Do Surge Protector Devices Work? 

Fully functional surge protection devices
Source: Pinterest

In a nutshell, an SPD limits the transient voltage and directs the current back to its source or ground when a transient voltage arises on the protected circuit.

To fully understand the precise mechanism underlying surge protector devices. Here is a detailed explanation of how surge protector devices work:

  • The electrical current from the outlet travels through a conventional surge protector to a number of electrical and electronic devices plugged into the power strip. The surge protector directs any excess power into the outlet’s grounding wire in the event that the voltage from the outlet surges, spikes, or increases above the acceptable level.
  • The additional voltage is diverted by a part known as a metal oxide varistor (MOV) in the most popular form of the surge protector. Similar to a pressure-sensitive valve, the MOV operates. The MOV reduces resistance when it notices high voltage levels. Resistance rises when voltage levels are too low. It will automatically engage in rerouting extra voltage. Three components make up the MOV: two semiconductors connecting the grounding and power lines to the central piece of metal oxide material.
  • These semiconductors exhibit a voltage-dependent variable resistance. The electrons in semiconductors flow in such a way as to provide an extremely high resistance when the voltage falls below a particular threshold. The behavior of the electrons changes when the voltage is higher, leading to a considerably reduced resistance. A MOV is inactive at the proper voltage. A MOV may conduct a lot of currents to remove excess voltage when the voltage is too high.
  • The MOV’s resistance increases once more as soon as the excess current is switched to the MOV and to the ground, which causes the voltage in the hotline to revert to normal. This allows the surge protector to continue powering any attached machines while the MOV just redirects the surge current.

The Different Types of Surge Protection Devices

Beny Surge protection devices
Source: Beny

There are several types of surge protection devices, and since each is designed for a distinct purpose, it is important to grasp the varieties. Surge protection equipment mostly comes in three different varieties. These are what they are:

  • Type 1 Surge Protector Device (SPD)

At the location of the power energy supply, an SPD Type 1 is fixed on the line side of the main service entrance. This kind is utilized for outdoor applications and has a current wave that lasts 10/350 seconds.

It guards against external power surges brought on by lightning or the switching of utility capacitor banks. It is regarded as the house or office’s first line of protection.

  • Type 2 Surge Protector Device (SPD)

In order to eliminate all overvoltage from supply circuits that are unlikely to be directly struck by lightning, SPD Type 2 is positioned on the load side of the main service entry. An 8/20 s current wave serves as this type’s defining feature.

Its primary job is to protect Mp/Mc-based boards and delicate devices by limiting transient voltage. Applications in business and industry use it.

  • Type 3 Surge Protector Device (SPD)

To safeguard the end user from overvoltage, SPD type 3 devices are employed. They could be added to supply networks that already have SDP types one and 2. Voltage waves (1.2/50 s) and current waves (8/20 s) make up Type-3 SPD.

Its primary purpose is to restrict low-level surges that could harm delicate electronic circuits in TVs, computers, and other electrical appliances. Power strip surge protectors are regarded as the last line of defense in a network that protects against surges.

Aside from the main three types, there are two more types of SPDs one ought to know, Type 4 and Type 5.

  • Type 4 Surge Protector Device (SPD)

Devices of the SPD type 4 are regarded as component SPDs. Typically, one or more Type 5 components are assembled to form component SPDs. Type 4 SPDs must be incorporated into other systems because they are not designed for standalone use.

These safeguard servo motors, PLCs, and other equipment used in industrial applications. They are also known as surge protection modules.

  • Type 5 Surge Protector Device (SPD)

Discrete component surge suppressors, or SPD type 5 devices, can be installed on a printed circuit board, connected by leads, or offered inside an enclosure with mounting hardware and wiring terminations. These devices include MOVs.

Applications of Surge Protection Devices

Applications of Surge Protection Devices
Source: Unsplash

Almost every household and industry’s electrical system structure must include surge protection devices. Here are a few real-world examples of surge protection device applications to help everyone understand how they might be used in various settings. 


Industrial surge protection devices protect machines. These devices can safeguard machinery and systems in factories and other industrial settings, including safety interlock circuits, control systems, and telecommunications. Devices for industrial surge prevention are commonly mounted on a DIN rail in a panel.


Industrial and commercial surge prevention are similar in many ways. The protective devices, however, are frequently put in building management systems for offices and commercial purposes. Systems and tools including elevators, data centers, emergency lighting, computing, and other electronics and control systems may fall under this category.


Compared to their industrial and commercial equivalents, domestic surge prevention devices are often better suitable for lighter-duty applications. To connect home appliances and electronic equipment, residential gadgets can be installed in consumer units, electric control panels, or surge-protected socket strips. Surge prevention for appliances can reduce safety risks from transient voltage and electrical surges and offer peace of mind.

Why Do We Need Surge Protection Devices? 

Light bulbs under surge protection
Source: Unsplash

Every household and enterprise needs surge protection devices to safeguard electrical equipment security. These gadgets are crucial for safety reasons in addition to helping to avoid loss or damage to delicate electrical equipment.

Below are some of the major reasons for power surges:

  • Downed power lines
  • Lightning storms
  • defective or damaged wiring
  • When supplying electricity, the utility company causes surges.
  • Turning high-powered electrical divorces off and on rapidly

Electrical protection is also advised and recommended in industrial areas by several regulations, such as the IET 18th edition standards. Power surges and transient voltage can pose a serious risk to people and equipment.

Knowing the risks connected with voltage spikes or surges will enable anyone to appreciate the value of surge prevention. Even while these occurrences only last a few nanoseconds or microseconds, the strain they exert on electrical equipment can be extremely strong.

Here are some benefits of surge protection devices that should further explain the importance of the devices: 

  • Protecting any area from potential dangers with surge protection devices is a cost-effective option. It is easy to safeguard any property with simple installation.
  • Surge protection devices can lengthen the lifespan of any electrical equipment and appliances by preventing burnout.
  • Surge protection devices can safeguard appliances, HVAC systems, and more because they control excessive voltage. The number of maintenance calls that are being made will go down as a result.

How to Choose the Ideal Surge Protection Device? 

Surge protection device connection
Source: Pinterest

Knowing the value of a surge protection device, the next move is probably to get the right surge protector for any electrical equipment. However, many different types of surge protection devices are available on the market, and they all have unique models and sizes designed for certain uses. 

Consider the following advice to choose the proper surge protection device less difficult rather than pondering which one suits the needs.

  • The structure’s proximity to lightning strikes
  • The equipment’s value and sensitivity call for protection
  • The kind of machinery used
  • The equipment’s location
  • The installation’s amount of exposure

Once people have the answers to these inquiries, they should be able to correctly identify the demands and choose a surge protection device that fulfills them. 

Next, after choosing the ideal surge protection device, check out whether it has the following aspects to ensure that the device is authentic or not.

  • Has the appropriate number of outlets or ports.
  • Make that it is a transient voltage surge protector and that it has the UL seal.
  • Check the energy absorption rating and clamping voltage.
  • Try to find a warranty.
  • Ensure that it has an indicator light.
  • Any surge protector that is being purchased must be UL-certified and adhere to a minimum of 1,449 requirements. To be referred to as a “transient voltage surge protector,” this is necessary.
  • Check the clamping voltage and energy absorption rating. First, the surge protector must withstand at least 600 to 700 joules of energy before failing. The voltage that activates the MOV is known as the clamping voltage. This should ideally be 400 volts or less.

The above-mentioned points will prepare anyone to purchase after confirming that the SPD truly possesses the attributes mentioned above. 

Common Surge Protection Device Options

Common surge protection device options
Source: Beny

When picking a surge protector, it is crucial to be aware of the available options as there are many types of surge protection devices. Types of common surge prevention equipment include:

  • Surge Protection Sockets

These are surge protection devices built into sockets or multi-socket strips. They are frequently applied in home settings.

  • Surge Protection Plugs

These are often plug-in adaptors or power connectors that connect to mains outlets and have surge protection incorporated into the gadget.

  • Telephone Surge Protection Devices

These serve as adapters for the linked RJ11 or RJ12 connection and provide built-in surge protection.

How Much Are Surge Protection Devices?

Knowing the significance of surge protection devices, one might quickly assume they can be quite expensive. But contrary to the expectations, surge protection devices are less expensive than anyone might expect.

Surge protection equipment typically costs between $70 and $300. This means that a high-end system may cost $300 or more, while a cheap system might only cost around $70.

However, the price estimate provided is for the surge protection device alone. Along with the installation charges, the price can be a little more expensive depending on the electric system and the electrician, and the other essential components required for installing the SPDs.

How To Install A Surge Protection Device? 

Man Installing A Surge Protection Device
Source: Unsplash

Surge protection equipment is designed to provide the highest level of security for any electrical equipment. The best option is to follow the step-by-step installation guide provided below to guarantee that the surge protection device is fitted correctly and performs its function flawlessly.

At the source of the supply to the property, surge protection (type 1 or type 2) ought to be installed. This can be fitted inside the current consumer unit, fed from it and fitted in its enclosure, or supplied from the supply tails and fitted in its enclosure.

After the main switch but before any RCDs, surge protection devices should be installed, and an appropriate fuse or circuit breaker should protect them.

Coordination of Protectors

Numerous institutions require multiple protective measures. In doing so, a higher discharge capacity is achieved while a reduced residual voltage is guaranteed.

A minimum distance of 10 m must be kept between protection devices to achieve coordinated actuation of protection stages based on various technologies. As a result, most of the energy is released by activating P1, the initial phase of protection. The second step (P2) will then reduce the residual voltage at the first protection device’s output.

A combination protection device must be employed, or decoupling coils must be installed to replicate the cable clearance in panels where the two protection stages are centrally located, and there is no 10 m clearance.

Connection Cabling

The length and kind of cabling are essential for the device to receive as little electricity as possible. The efficiency of overvoltage protection is decreased as feed wires to the protection device get longer. These conductors should be as brief as feasible for the best protection. The efficiency of a V-cable can diminish this effect on the input and output device.

Regarding the current path, the total length of the conductors should be between 0.5 and 1 meters.

LIVE + CPC = <0.5M (Max 1M)

NEUTRAL + CPC = <0.5M (Max 1M)

To further eliminate smaller transients, type 3 protection should be positioned close to the equipment it protects if it is necessary for sensitive electronics.

End of Life of the Surge Protection Device

The surge protection device needs special consideration regarding its end of life. Every time there is a lightning strike, its parts get older.

A surge protection device’s internal device disconnects it from the supply when it reaches the end of its useful life. The status that necessitates the replacement of the pertinent module is shown by an indicator fixed in the protector and alert feedback.

  • Visual Indication: Models with a viewer for local end-of-life signaling of the protective device are available.
  • Remote Indication: Dry contacts are used in models with the remote indication (IR) to remotely signal the protector’s end of life.

The surge protection device may short circuit and be destroyed if its limit capacities are exceeded. The surge protection device must consequently have a device fitted in series upstream of it.

Back-up Fuses

Surge protection devices are connected in parallel with the installation to be protected downstream of a circuit breaker or fuse. Installing a second disconnection element, F2, may be necessary, depending on the size of the fuse. In particular, where the caliber of F1 exceeds a specific value, the installation of the F2 element is required. The technical literature for each protector specifies this value, which varies for each protection.

Safety Tips to Follow

A safety helmet
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Surge protectors protect electrical devices from accidental voltage spikes that may harm the electrical devices and the person using them. So naturally, when it comes to installing it, everyone should follow some safety tips. They are:

  • Never connect a surge protector to an extension cord, power strip, or another surge protector.
  • Install surge protectors indoors in a dry area. Aquariums should not be used with surge protectors.
  • Verify that the surge protector can support the current amperage demands of the connected devices.
  • Never exceed the surge protector’s electrical rating.
  • If the surge protector comes with a power cord, keep it exposed and unwound before use.
  • Examine the surge protector regularly to check for wear indicators like frayed wires or damaged outlets and whether it feels warm to the touch.
  • The electrical devices may suffer from a lightning strike or other power surges. Choose the best surge protectors for any residential home to lessen the risk of voltage bursts harming the electric appliances, such as televisions, sound equipment, computers, and laptops.


Surge protection devices are a must in every household and industry. These devices ensure that the electric system and the people nearby are safe from any unprecedented electric power surge. With the appropriate Surge protection device, one can feel at ease at the home, office, and anywhere. If you are on a hunt for SPDs for your business or wholesale, you could visit which provides you with a range of durable SPDs that ensure seamless performance for a long time.

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