3 Phase Surge Protector

How To Choose The Ideal Three Phase Surge Protection?

Created by: Glen Zhu | Updated Date: Sep 20, 2022

How To Choose The Ideal 3 Phase SPDs

Every electrical system requires a variety of components to control and secure the current flow because electricity has always been a life-threatening invention that also makes daily living easier.

New types of surge protectors are now necessary as a result of technological advancement, the three phase surge protector is one instance.

Everything you need to know about the 3 Phase surge protection device, including how they operate, their advantages, and how to choose one, will be covered in this blog post.

Understanding Three Phase Power

Three-phase power is a three-wire AC power circuit with each phase ac signal 120 electrical degrees apart. The diagram below shows a typical three-phase AC wavelength:

Typical three phase AC signal

What is a 3 Phase Surge Protector?

3 phase surge protection devices, or three phase SPDs for short, are unique and significant electronic tools used to safeguard the wiring in the consumer unit and other electrical installations against transient overvoltages on 3 phase alternating current (AC) power lines.

How does a three phase surge protection device work?

In the simplest terms, a solar SPD controls the transient voltage and directs the current back to its source or ground when a transient voltage arises on the protected circuit.

To function, there must be at least one non-linear component of the SPD, which under different conditions transitions between a high and low impedance state.

The SPDs are in a high-impedance state and have no impact on the system at typical operating voltages. When a transient voltage occurs on the circuit, the SPD moves into a state of conduction (or low impedance) and diverts the surge current back to its source or ground. This limits or clamps the voltage to a safer level. After the transient is diverted, the SPD automatically resets back to its high-impedance state.

Application of 3 phase industrial surge protectors

Application of 3 phase industrial surge protectors

Three phase SPD is not typically used in residential applications except for clothes dryers or electric ovens. Instead, it is typically used in industrial applications and commonly mounted on a DIN rail in a panel.

These devices can safeguard machinery and systems in factories and other industrial settings, including safety interlock circuits, control systems, and telecommunications. They are costly to the company owner: the price may be enormous and the failure, or even replacement, of those devices, would incur a major financial loss, possibly putting the very existence of the company at stake. The key aspects, from the perspective of trade unions, are the employees: they operate electrical equipment and, in the event of a surge, their lives might be at risk.

3 phase industrial surge protection devices are thus necessary to protect electrical equipment from voltage transients on three phase alternating current (AC) power lines.

3 Phase Surge Protector Working Principle

Surge protection devices contain at least one non-linear component (a varistor or spark gap), the electrical resistance of which varies with the voltage applied to it. Their purpose is to redirect discharge or impulse current and limit overvoltage at downstream equipment.

To completely comprehend the mechanism underlying three phase SPD. Here’s a more in-depth explanation of how it works:

  • During normal operation (e.g., in the absence of surges), the surge protection device has no influence on the system where it’s installed. It acts as an open circuit and maintains the isolation between the active conductors and the earth.
  • When a voltage surge occurs, the surge protection device reduces its impedance within a few nanoseconds and diverts the impulse current. The surge protection device behaves like a closed circuit, the overvoltage is short-circuited and limited to an acceptable value for the electrical equipment connected downstream.
  • Once the impulse surge has stopped, the surge protection device will return to its original impedance and return to the open circuit condition.
The working principle of surge protector

3 Phase Surge Protector Wiring Diagram & Intallation

Wiring Diagram:


3 Phase Surge Protector Installation

4 Signs You Should Replace Your 3 phase SPD

Unfortunately, it is a mistake to assume that your devices are 100% protected from surges with a surge protector. There are many reasons surge protectors may fail. For instance, surge protectors simply are not designed to last forever.

> How Many ‘Hits’ Has it Received?

When determining whether a surge protector is defective, one should take into account how frequently it has been put to use.

A surge protector’s capacity is measured in joules, rather than years.

Typically, this is a fixed amount, like 1000 joules. This is the maximum amount of electricity the gadget can take in before losing steam.

For example, if your protector receives ten ‘hits’ of 100 joules, then it will be tapped out.

> Check the Light

You might be able to tell when to replace the surge protector simply by checking for the end-of-life indicator on the SPD which signals the status of the device. Not all surge protectors have these, but many modern ones have them as a standard feature.

Simply look at the visible window of your 3 Phase surge protector to see if you can see a red (End of life) or green (Normal) sign.

Thanks to pluggable cartridge for easy replacement when failing without shutting down the power

> Check Your Insurance

One thing that is worth noting is that many insurance policies will NOT cover power surge damage if there is no surge protector in place.

Likewise, some insurance providers may even choose not to cover your losses if you are found to have been relying on an old, expired surge protector.

Insurance depends on responsible owners. Cover your bases by keeping your surge protectors up-to-date.

> Call an Electrician

A three phase surge protector won’t help you if your electrical system is broken. Make sure to contact a qualified electrician to get any broken electrics working properly once more & replace with a suitable product.

Finally, replace the device right away if you see any frayed wires, it isn’t functioning properly and/or is hot to the touch, or it doesn’t have an internal circuit breaker in your model.

How To Choose The Ideal Three Phase SPDs?

3 phase surge protection devices are an important part of any electrical system, especially in industries where sensitive equipment is used. They are available in a variety of designs and ratings, and choosing the right one is critical to ensuring the safety of the equipment.

Now that you know what a 3 phase surge protector is and how it functions, you should be ready to purchase one for your electronics.

The following are the key points to bear in mind:

> Choose a suitable SPD according to the parameters in the table below:

Three Phase Surge Protection Device SPD family

EN 61643-11:2012

IEC 61643-11:2011

VDE 0675-6-11:2002

In (80/20μs)

Imax (8/20μs)

Iimp (10/350μs)

Uoc (1.2/50μs)

Type 1

Class I

Class B

25 kA

100 kA

25 kA


Type 1+2

Class I+II

Class B+C

20 kA

50 kA

7 kA



Type 2

Class II

Class C

20 kA




Type 2+3

Class II+III (or III)

Class C+D (or D)

10 kA



20 kV

5 kA

10 kA

10 kV

AC SPDs standards and test classification

> Get the right number of ports or outlets.

Be careful to select the appropriate surge protector for your requirements. What equipment will be connected to it? Amount of ports required?  Currently, some protectors have up to 12.

> Check to see whether it is a transient voltage surge protector and if it has a TUV mark.

Verify the device’s TUV mark. Never take the tag off the protector because it provides crucial testing information that you’ll require in the event of a problem.

> Check the clamping voltage and energy absorption rating.

Check the device’s energy absorption rating to find out how much energy it can withstand before failing. The ideal range is between 600 and 700 joules; the greater the number, the better.

> Make sure it has an indicator light.

Choose one with an indicator light that lets you know when the MOV has worn out. Many will continue to work but without surge protection in place.

Simply said, the more informed you are before you buy, the better your chances of protecting your expensive equipment.

Which Device To Install upstream of Your Three Phase SPD, Fuse or Circuit Breaker?

As well known, coordination between a surge protective device and its circuit breaker(or fuse) is critical in an electrical system. Which device should be installed upstream of the three phase SPD in your project? We’ll give the answer below:

*Coordination between the surge protective device & its circuit breaker in the event of a short circuit.

Below table shows: the rating, curve and short circuit current level of the circuit breaker coordinated with the SPD.

Coordination between the surge protective device and its disconnect circuit breaker in the event of a short circuit
*Coordination between the surge protective device and its fuse in the event of a short circuit
Coordination between the surge protective device and its disconnec fuse in the event of a short circuit

Differences Between Circuit Breaker & Fuse

> Different protection methods

The fuse’s protection method is fusing, and when the fault phenomenon is eliminated, it is necessary to replace the fuse to restore the power supply, making it inconvenient for maintenance.

The circuit breaker uses tripping as its protection method. After the fault is removed, the normal power supply can be restored only by closing the circuit, making it far more convenient to maintain and recover than a fuse.

> Different speed of action

The fuse’s fusing action speed can reach the microsecond (s) level, which is much faster than that of the circuit breaker. This capability is typically more appropriate for installation in situations requiring similar fast cut-off.

The circuit breaker’s tripping action speed is millisecond (ms), which is much slower than that of the fuse, so it can only be used in situations where the cut-off speed requirement is not very high.

> Different times of use

After performing fault protection and blowing the fuse, the fuse must be replaced. On the contrary, the circuit breaker can be reused in most cases.

> Different working principle

Fuse: mainly based on the thermal effect of the current. When the current exceeds the fixed value, the internal fuse will cause the occurrence and fuse to break the circuit and protect the equipment from being burned out by the large current.

Circuit breakers: There are many types of circuit breakers and there are differences in structural principles. Typically, it is because the current is too large that the excitation of the trip coil will cause the circuit breaker to perform the trip action. Of course, the circuit breaker can not only operate automatically, but also manually control the circuit breaker’s opening and closing action.

Refer to the above to choose suitable fuse or circuit breaker in front of your three phase SPD.

How Much Are 3 Phase SPDs?

Knowing the significance of three phase surge protection devices, one might assume they are quite expensive. Surge protection devices, however, are less expensive than most people expected.

Equipment for surge protection typically ranges in price from $70 to $300. A high-end system could cost $300 or more, but a low-cost system might only cost about $70.

The price estimate provided, however, is for the surge protection device alone. Along with the installation fees, it could be slightly higher depending on the electric system and the electrician, as well as the other necessary components for installing the SPDs.

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Three Phase Surge Protector Price

LSP’s reliable 3-Phase Surge Protection Device SPD is designed to be installed close to equipment to protect against transient overvoltages.

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