Single Phase Surge Protector

How To Choose The Right Single-Phase Surge Protection Device?

Created by: Glen Zhu | Updated Date: Sep 23, 2022

How to choose single phase surge protector SPD

Understanding Single Phase Power

Single-phase power is the most common form of AC power delivery. As you could expect, single-phase power produces a single wave of power, The diagram below shows a typical single-phase AC wavelength:

Typical Single phase AC signal

What Is A Single Phase Surge Protection?

Single phase surge protection device (single-phase SPD) is designed to protect equipment from transient overvoltages present on single-phase alternating current (AC) power lines.

How Does A Single Phase Surge Protection Device (Single Phase SPD) work?

Simply said, a single-phase surge protector limits the transient voltage and guides the current back to its source or ground when a transient voltage occurs on AC single-phase power lines.

One single surge arrester contains at least one non-linear component (a varistor or spark gap), its electrical resistance varying in the function of the voltage which is applied to it. Their function is to divert the discharge or impulse current and to limit the overvoltage at the downstream equipment.

Single Phase Surge Protector Working Principle

In normal use (no overvoltages): Single phase 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 there is an overvoltage: Single phase surge protection device becomes active and guides the current back to its source or ground. 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.

When the overvoltage has been discharged: Single phase surge protector will return to its original impedance and return to the open circuit condition.

The working principle of surge protection device

Single Phase Surge Protection Device Wiring Diagram

How To Install A Single Phase Surge Protector?

Our LSP team recorded a video for better clarity for you:

How to Install Single Phase Surge Protector

Installation Rules To Follow

Surge Protection Device SPD Installation and Wiring Diagram

> Connection Length of SPD Circuit

When installing a single-phase surge protector, remember that the golden rule for cable lengths and clearance distances is “the shorter, the better.”, which determines surge protectors’ overvoltage absorption capacity.

* The 50-centimeter installation rule- between cable & SPD

The ’50-centimeter rule’ is a general guideline for how long a cable should be between a single-phase surge protector and the mains network. Overlong cables might damage loads. Inductance increases under fast rise time conditions, causing high transient voltages to accumulate in long cables.

Indeed, the shorter the connection, the more effective the protection. More than any other parameter cable length determines a surge protector’s ability to dissipate overvoltage up to a given value.

* The 10 meters installation rule- between single phase surge protectors & equipment

If they are longer than 10 meters, install a second surge arrester as close to the equipment as possible. Use the same surge arrestor brand and follow the manufacturer’s coordination table.

> Location of Single Phase SPDs

In order to limit overvoltages as much as possible, note that the first level of surge protection device must be installed as far upstream as possible of the installation in order to reduce as much as possible the induced effects of the lightning by electromagnetic coupling.

Don’t forget about it. Transients can enter a building or facility via phone lines, computer networks, CCTV systems, and any other means. Install single-phase surge arrestors on any device or system that is vulnerable to overvoltage.

> Coordination

If the surge protection device exceeds its limitation capacity, it may be destroyed by short-circuiting itself. Coordination between a surge protective device and its circuit breaker (or fuse) is therefore critical in an electrical system.

> Compatible With the Earthing System

It is essential to check that the surge protection devices used are compatible with the earthing system

End Of Life Of Single Phase Surge Protection

However, single-phase surge protectors simply are not designed to last forever.

The single-phase SPD is a device whose end of life requires particular consideration. Every time lightning strikes, its parts get older.

At the end of life, an internal device in the single-phase surge protection device disconnects it from the supply. The visible window of your single-phase surge protector indicates this status (red sign – end of life), which requires the replacement of the module concerned.

Application Of Single Phase Surge Protectors In Home Or Whole-house

Most homeowners know that power surges can damage sensitive electronic equipment. Many assume that lighting strikes are the only cause for concern.

However, surges generated from devices within the house are far more common, occurring up to 100 times a month, cumulatively shortening the lifespan of household electronics.

Single-phase power is the most common form of AC power delivery. Because residential power requirements are generally much less than business power requirements, single-phase SPD is sufficient for our home.

Single Phase Protection Single Phase SPD For Home Whole-House

How can you prevent power surges for your home?

  • Install a single-phase surge protector throughout the entire home. (Even if your home has a single-phase surge protector for the whole thing, it’s still important to install extra security for sensitive electronics like laptops and refrigerators.)


  • Single-phase surge protectors for cable lines and phone lines.


  • Use the proper UPS and power strips to safeguard computers and other electronic sensitive equipment.

Application Of Single Phase Surge Protectors In Small Business

Single Phase Protector for business Single Phase SPD

Small businesses are often overlooked when it comes to surge protection. But the truth is, they are just as vulnerable to power surges as larger businesses.

In fact, power surges are one of the most common causes of sensitive electronic equipment (for example office computers) damage and data loss in small businesses.

Investing in single-phase surge protection is an important step in protecting your small business. Not only will it help to safeguard your business from damage, but it can also help to protect your employees and customers.

Single-phase surge protection devices are thus necessary for small businesses to protect sensitive electronic equipment from voltage transients on single-phase AC power lines.


To keep your sensitive electronic equipment safe, select the best single-phase surge protector at all times.

Visit if you’re looking for durable single-phase SPDs to assure dependable performance over a long period of time for your business or home. Our LSP team would be happy to assist you with professional & experienced engineers backing up.

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Single Phase Surge Protection Device SPD Price

LSP’s reliable single-phase surge protection device SPD is designed to be installed close to equipment to protect against transient overvoltages.

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