Surge Protection


surge protection

Surge Protection Devices

Most commercial, industrial and residential premises now play host to a wide range of electronic equipment. This can range from industrial control equipment to security alarms, computers, television and microwaves. All electronic items can be vulnerable to power surges, or transient overvoltages, which can cause damage and degradation to the electronic equipment.

What Is A Transient Overvoltage?​

A transient overvoltage (or surge) is an increase in voltage between two or more conductors which lasts for a short duration. This could be for a time period from microseconds (millionths of a second) to a few milliseconds (thousandths of second). Although the surge lasts a minuscule amount of time, the damage that can be caused by such surges can lead to early degradation of equipment, downtime need to repair damage caused by such surges or irreparable damage to electronic components by overloading or shorting out the electrical components.

How to protect from transient overvoltage?

Surge Protection Devices (SPDs) can be installed to provide protection against transient overvoltages, which will prevent electrical and electronic equipment being damaged by such surges as may result from switching of transformers, lightning, motors and lighting. The Surge Pro­tec­tion Device attempts to lessen the voltage supplied to electrical and electronic equipment by either blocking or shorting to ground any voltages above a safe standard, thereby protecting the electrical and electronic equipment from the voltage surge. Once installed, the SPD needs minimal maintenace.  The unit usually has an indication window which shows if they are operational or if they have reached ‘end of life’ and need replacing.  Usually there is a cartridge which can be easily replaced to ensure the device is operational again. 

Why should a Surge Protection Device be installed?​

A Surge Protection Device will help protect sensitive electrical and electronic equipment from transient overvoltages, ensuring the longevity of your equipment, saving you time and money.  There is also a legal requirement in some cases to ensure a Surge Protection Device is installed - the latest edition of the BS7671 regulations (18th edition) now stipulate that such protection must be provided in certain circumstances – see below for more information.

Current Regulations:

The 18th Edition BS 7671 now stipulates that protection against transient overvoltages must be provided where the consequences caused by an overvoltage could:

  • Result in serious injury to, or loss of, human life, or
  • Result in serious interruption of public services and/or damage to cultural heritage
  • Result in interruption of commercial or industrial activity, or
  • Affect a large number or co-located individuals.

For all other cases, a risk assessment according to regulation 443.5 shall be performed in order to determine if protection against transient overvoltages is require. If the risk assessment is not performed, the electrical installation shall be provided with protection against transient overvoltages.

For a single dwelling unit it will be a decision for the house owner to make whether the consider the small additional cost of the surge protection device justified to protect their installation and equipment against these damaging overvoltages.

Contact us now for advice on suitable surge protection for your premises from one of our experienced Electrical Engineers.

At a Glance | Surge Protection 

All of the key info you need to know about Surge Protection Devices provided courtesy of Hager 

Bitesize Guide | 18th Edition 

Hager’s helpful guide to everything you need to know about the 18th edition.   

Hager’s Residential Distribution Catalogue contains all of their 18th edition solutions for residential applications.

Reality check Infographic

Hager’s helpful Reality Check Infographic 


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