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Electrical Spikes and Surges

This web page describes:

  • What an electrical spike is.
  • Why it is called an electrical spike.
  • What problems an electrical spike causes.
  • How to protect against electrical spikes.

What Is An Electrical Spike (Surge)?

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


Why Is The Increase In Electrical Supply Called A Spike?

Short-term increases in the electrical supply voltage, or current or both, are called ‘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.


The image below is an oscilloscope display.


The oscilloscope display shows the electrical supply voltage level (red line).


Electrical spike displayed on an oscilloscope


The normal UK electrical supply voltage is 240 volts.


The red line on the display shows that the electrical supply voltage is 240 volts most of the time.


An electrical surge causes the supply voltage to increase from 240 volts to 600 volts for a short period of time.


The short-term increase in voltage causes the oscilloscope display (red line) to increase; the supply voltage soon goes back to 240 volts and the red line goes back down.


The red line that represents the supply voltage value looks like a spike, hence the name ’electrical spike.


What Problems Does An Electrical Spike (Surge) Cause?

RCD Problems

Electrical spikes often cause RCDs to trip.


The effect of an RCD tripping can be no electrical power to a house or workplace or part of a house or workplace; reset the RCD to restore power.


RCDs are safety switches that prevent high currents and voltages flowing in an electrical circuit.


About RCDs


Find, reset and investigate a tripping RCD


How to reset and RCD


Damage To Electrical Appliances

The surge in voltage, or current or both, can damage electrical appliances, for instance PCs, televisions and sound systems. The electrical surge can damage any electrical appliance that is plugged in.


An electrical spike can also damage internet routers and modems if the electrical spike ‘gets into’ the telephone circuit.


More often than not the only solution is to replace the electrical appliance.


How To Protect Against Electrical Spikes

It is possible to prevent, or lessen, the damage from an electrical spike.

Putting electrical spike protection into an electrical circuit is called ‘surge protection’.

Surge protection can be as simple as putting an adaptor into an electrical socket; electrical surge protection can also be complex and expensive.


About Electrical Surge Protection


Judge Electrical Limited
15 Mulberry Court, Huntington, York, YO32 9TU
Telephone 01904 764845 (Landline), 07919 033113 Mobile)
Email info@judgeelectrical.co.uk
VAT No. 852917405. Company Number 6359328