How does a Surge Protector work?

I want to know how they work.

1. What does the glowing green light for Wiring mean? What does the glowing red light for Surge mean?

2. What do I do to make sure it protects my equipments from surges, spikes?

3. Is it meant to be switched off when before I sleep? Does it only protect from spikes when it is switched On?

4. Why is there even a switch On and Off button?

5. Do I ALWAYS leave it on?

These are the questions I want to know about a Surge Protector.


The part that makes a surge protector "work" is called a Metal Oxide Varistor (MOV).

The protective action is obtained due to the MOV's electrical behaviour:

Normally, its resistance is almost infinite, but when the voltage across it

exceeds a certain value (usually about 3 times the normal line voltage)

the resistance suddenly drops, causing the MOV to pass a large current.

This essentially absorbs the surge before it can harm the devices

plugged into the protected outlets.

1. The "Wiring" light indicates that the surge protector

is correctly connected to the power line.

The "Surge" light could indicate either that a surge has occurred,

or that the protector is still good, depending on the design of the

protector. You would need to refer to the information for the

specific protector to find out which it is.

2. Making certain that it will actually do any good is impossible, but

using it as intended will most likely be better than doing anything else.

3. Switching it off is entirely optional with the user (you).

Switching it off is almost the same as disconnecting all the

things plugged into it, which is the best protection of all.

It actually doesn't do anything when switched off.

4. The switch is provided for convenience, so that if you want to

switch off the power to whatever is plugged into it, you can do so.

Many of the switches used in recently-made outlet strips are also

circuit breakers, and if tripped, they are reset by switching off, then back on.

5. See answer # 3.