- What is a surge protector?
- Why use it?
- How surge protection works
- Blow a fuse, not your equipment
- Insidious spikes and sags?
- Line noise
Why use it?
Components in today's electronic devices (including everything from computers and entertainment systems to home appliances like microwave ovens) are smaller and more delicate than their predecessors, and thus more sensitive to fluctuations in current. Microprocessors, in particular, require stable current at the right voltage -- a nice, steady flow of 240V mains power.
Unfortunately, electrical power quality changes frequently, even hourly. Anything over the standard voltage is called a "transient" and, depending on its severity and duration, can also be called a "spike" or "surge". Even though they may be so brief that they are measured in nanoseconds (billionths of a second), they can still damage your equipment. A surge lasts three nanoseconds or more; a spike only lasts 1-2 nanoseconds but both can cause damage.
Surges, spikes and sags occur daily. Many are virtually unnoticeable, but inevitably, some stronger power pulses will cause damage -- either immediately or over a period of time.
The time before and after an outage (blackout), especially during a thunderstorm, is characterised by noticeable surges and sags, much like how tremors are felt before and after an earthquake. Even if you do not personally notice these fluctuations, your unprotected electronic equipment will.
How surge protection works
A surge protector usually works by channelling any extra voltage into the electrical outlet's "earth" or "ground" wire, thus stopping it from reaching your equipment. At the same time, it still allows the normal voltage to continue.
In the most common type of surge protector, the extra voltage is diverted by a component called a metal oxide varistor, or MOV. A MOV provides strong surge protection, but degrades each time. It may even last only once.
Another common (and cheaper) type of surge protection is provided by a gas discharge arrestor (gas tube). It uses an inert gas which only becomes conductive under a strong surge of electricity, then diverts the excess harmlessly to "ground".
Silicon Avalanche Diodes (SADs) are known for their fast response time and low voltage clamping level. Clamping voltage is the maximum amount of voltage that a surge protector will let through before it suppresses the surge by conducting electricity to the ground line. The lower the clamping voltage the better the protection. A plus for SADs is that unlike MOVs, they don't degrade with repeated surges so they last longer. But MOVs provide better strong-surge protection.
The best -- but naturally, more expensive -- surge protectors include a combination of SADs and MOVs and possibly gas tubes as well.
Blow a fuse, not your equipment
Some models also have a fuse within the surge protector. When a surge occurs, the protector routes the increased voltage to the grounding wire, but if the voltage is too great, it will blow the fuse. The unit can be re-used when the fuse is replaced. Happily, so too can your equipment.
While computers typically come with some measure of surge protection built into the power supply unit (PSU), this is nowhere near as robust as a dedicated surge protection device, which may also include line conditioning and data line protection, along with surge protection for several devices.
TIP: A power filter device can be, and should be, used for more than just protecting your computer. To be safe from harm, ALL electronic equipment around the home or office should be connected to mains power via a power filter, as all this equipment is sensitive to power fluctuations and can be damaged.
Insidious spikes and sags
It is important to note that not all damage to electronic equipment is caused by a massive electrical surge. Most often, power-related equipment failure is due to the "wearing down" of your components over months or years of exposure to relatively mild electrical spikes until, eventually, they burn out.
Sags, also known as brownouts, also cause long-term damage. These are momentary drops in voltage often shown by dimming or flickering lighting. Like spikes, they are very common and can cause hardware crashes and even damage. On a computer, they can also create instability such as computer "freezes" or unexpected reboots, lost settings or even data corruption.
Some surge protectors have a line-conditioning system for filtering out "line noise" (smaller fluctuations in electrical current). Noise can be generated by equipment on the same power circuit or by nearby devices, such as heavy machinery, motors, compressors, radio transmitters etc. Like spikes and sags, noise can cause intermittent and hard-to-trace problems with equipment, and eventually cause equipment failure.