Electrical Surge Protection


Electrical Surge Protection

This web page is about electrical surge protection. What an electrical surge is, what causes electrical surges, what damage an electrical surge can cause, how electrical surge protectors work and how to protect against an electrical surge.


What Is An Electrical Surge?

An electrical surge is a temporary, very short (less than a second), increase in the electrical supply voltage or current or both.

Another name for an electrical surge is a ‘spike’ in the supply. People call electrical surges ‘spikes’ because if you look at the electrical supply with some types test equipment, for instance an oscilloscope, the rise in voltage (or current or both) looks like a spike on the oscilloscope display.

Electrical surges can vary in size from a couple of hundred volts to many millions of volts. This is why Electrical Surge Protection is so important


What Causes Electrical Surges

Electrical surges are disturbances to the electrical supply. This is why Electrical Surge Protection is so important


Many different events can cause electrical disturbances for instance:

    • A nearby lightning strike.


    • Power coming back on after a power cut.


    • Turning on a major domestic appliance, for instance a fridge or cooker.


    • Contractors severing a nearby power line.


What Damage An Electrical Surge Can Cause

An electrical surge can destroy microcomputers.

Microcomputers are the most vulnerable domestic appliance.

A PC contains many microcomputers. ‘Electronic appliances’ like TVs, Hi-Fi and game consoles also contain microcomputers.

Most domestic appliances contain microcomputers, for instance washing machines, cookers, and central heater timers.

An electrical surge can destroy a microcomputer so making the parent appliance, for instance the PC or game console, useless.

An electrical surge can damage any electrical appliance that is plugged in. This is why Electrical Surge Protection is so important

All electrical parts are vulnerable to electrical surges. Electrical parts are designed to withstand an electrical surge of a certain level, usually about double the normal electrical supply.

An electrical surge of more than about double the normal supply can damage electrical parts. Most domestic appliances are not ‘built for repair’, damaging an internal electrical part usually means replacing the appliance, for instance a lamp or air-conditioner. This is why Electrical Surge Protection is so important


How Electrical Surge Protectors Work

Electrical surge protectors work by diverting the extra energy in the electrical surge away from the main circuit, usually to ’earth’.


Electrical Surge Protection


The diagram above shows the electrical surge protector when their is no electrical surge.


In normal circumstances the electrical flow is along the ‘Live’ line (red), through the electrical surge protector, through the electrical appliance and back to the mains supply by the ‘Neutral’ line (black).

Electricity flows through the electrical surge protector from connection 1 to connection 2 (green arrow).




If the electrical surge protector detects an electrical surge it diverts the extra electrical flow to earth.

When the surge protector detects an electrical surge it opens the path between connection 1 and connection 2 and closes the path between connection 1 and 3.

When their is an electrical surge the electrical flow is from the ‘Live’ line (red) through connection 1 of the electrical surge protector then to earth by connection 3 (green arrow).

The extra electrical flow taken away from the electrical appliance and sent to the earth line.

If the extra electrical does not flow through the electrical appliance it cannot damage the electrical appliance.


How to Protect Against An Electrical Surge (Domestic Property)

Electrical surge protection starts with good earth bonding. No electrical surge protector will work without good earth bonding. Electrical surge protectors work by diverting the extra electrical flow to earth. If the earth bonding of the electrical circuit is not good the surge protector will not work well.

Improving earth bonding is not expensive; the Judge Electrical 2015 guideline price for domestic earth bonding is £200 (UK).

Turn off and disconnect electrical appliances during a lightning storm or a power cut. Nearby lightning strikes and power restoration after a power cut are major causes of electrical surges.

If you disconnect electrical appliances during a lightning storm any nearby lightning strike will not affect the electrical appliances. If you disconnect electrical appliances during a power cut the electrical appliances will not be affected by any electrical surge when power is restored.


Use ‘Point Of Use’ Electrical Surge Protectors



‘Point of use’ means where you connect the electrical appliance to the electrical supply.


Most ‘point of use’ surge protectors look like a normal mains ‘multi-socket’ extension. The image above shows a UK ‘point of use’ electrical surge protection device.


The surge protector shown above costs about £13 (UK).


Use ’Internet Connection’ Electrical Surge Protectors

Electrical surges can happen on the telephone line. ’Internet connection’ electrical surge protectors fit into the telephone (data) line to a PC or laptop.

The telephone line (internet connection) cable normally plugs straight into the PC or laptop from a wall socket. Instead of plugging straight into the PC or laptop the internet connection plugs into the electrical surge connector. Another cable goes from the electrical surge protector to the PC or laptop.



The internet connection surge protector shown above is a Belkin ‘MasterCube’. The cost is about £10 (UK).


The MasterCube plugs into an electrical socket, the internet connection input and output lines are on the bottom of the MasterCube.


The MasterCube also has an UK electrical socket on the front so that you still have use of the socket that the MasterCube plugs into.


Contact An Electrician To Install Electrical Surge Protectors To Your Electrical Supply

There are many different types of electrical surge protectors that can fit to your electrical supply.

The costs (parts supplied) to install will be from about £150 (UK) upwards. The surge protectors are, in broad terms, the equivalent of the domestic surge protectors described above but they fit to the electrical supply.

Surge protectors that fit to the electrical supply are better as they divert the electrical surge away from many electrical appliances. An electrician can fit a surge protector to, say, the electrical line that supplies all the mains sockets. Fitting a surge protector to the electrical line that supplies the mains sockets protects all electrical appliances in the house.

Surge protectors that fit to the mains supply are usually better quality; they provide more protection than the simple ‘plug in’ surge protectors. This is an important part of Electrical Surge Protection


How to Protect Against An Electrical Surge (Commercial Property)

The first question to ask is ‘how valuable to your business are the electrical appliances in the property’? If the electrical appliances are ‘business critical’, spend the money to protect them.

Most businesses have many of the most vulnerable appliances – PCs, laptops, telephones. How would your business manage without any PCs, laptops or telephones?

The best approach is a ‘multilayer’ electrical surge protection system. A multilayer surge protection system means having more than one surge protector protecting electrical appliances. For instance a business may have a lightning rod, surge protectors on the main electrical supply line and ‘point of use’ surge protectors.

Specialist IT companies should consult a specialist IT Security Company. A specialist IT Security Company can supply the ‘complete package’; for instance electrical surge protectors, interruptible power supplies (UPS) and data backup.

No electrical surge protection system gives 100% protection. No system is 100% effective; no surge protector has exists that can protect against a direct lightning strike of millions of volts.

Costs of protecting commercial property range from about £500 (UK) for very basic protection to hundreds of thousands of pounds (UK). Spend the suitable amount of money for your business. This is why Electrical Surge Protection is so important




back-button Electrical Surge Protection Section Site Map