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.

Electrical surges are disturbances to the electrical supply. 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.

   

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. 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.

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

• 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.

   

• 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.

 

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