Surge Protection

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The main job of a surge protector is to protect electronic devices from “surges.” So if you’re wondering what a surge protector does, the first question is, “What are surges?” And then, “Why do electronics need to be protected from them?”

A power surge, or transient voltage, is an increase in voltage significantly above the designated level in a flow of electricity.The standard voltage is 240 volts. If the voltage rises above 240 volts, there is a problem, and a surge protector helps to prevent that problem from destroying your computer and other sensitive electronics in your home.

If the surge or spike is high enough, it can inflict some heavy damage on your electronics. The effect is very similar to applying too much water pressure to a hose. If there is too much water pressure, a hose will burst. Approximately the same thing happens when too much electrical pressure runs through a wire — the wire “bursts.” Actually, it heats up like the filament in a light bulb and burns, but it’s the same idea. Even if increased voltage doesn’t immediately break your machine, it may put extra strain on the components, wearing them down over time.

What can surge protectors do to prevent this from happening?

When a surge is detected the surge protector diverts the extra electricity to earth smoothing out the power supply to your equipment

The most common type of surge protector, uses a component called a metal oxide varistor, or MOV, which diverts the xtra voltage. As you can see in the diagram below, an MOV forms a connection between the active (Hot wire) power line and the grounding line(earth).


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A MOV has three parts: a piece of metal oxide material in the middle, joined to the power and grounding line by two semiconductors.

These semiconductors have a variable resistance that is dependent on voltage. When voltage is below a certain level, the electrons in the semiconductors flow in such a way as to create a very high resistance. When the voltage exceeds that level, the electrons behave differently, creating a much lower resistance. When the voltage is correct, a MOV does nothing. When the voltage is too high, a MOV can conduct a lot of current to eliminate the extra voltage.

As soon as the extra current is diverted into the MOV and to ground, the voltage in the active conductor returns to a normal level, so the MOV’s resistance shoots up again. In this way, the MOV only diverts the surge current, while allowing the standard current to continue powering whatever machines are connected to the surge protector. Metaphorically speaking, the MOV acts as a pressure-sensitive valve that only opens when there is too much pressure.