- 29 July, 2005 10:41
Let's get this sorted right upfront: ALL electronic equipment that plugs into a wall, needs protection. Without it, your expensive home theatre, sound system, TV, entertainment centre or computer equipment will likely be damaged by the surges, spikes, sags and brownouts that afflict our electrical systems. You may not see the damage until the system fails, but it can still be there, gradually "eating away" at your electronics. Power protection devices are most commonly called "surge protectors". Types vary, but the solution is simple. The best devices include combined surge/overload protection, power conditioning and noise/interference filtering. Let's look at how they can save you from the damage caused by unregulated mains power.
What is a surge protector?What is a surge protector?
Basically, this is a device that sits between your PC or other electronic equipment and the electrical mains (AC) outlet (ie, wall plug) and protects your equipment's power supply (and possibly communications lines) from electrical surges. Any power from the mains must pass through the surge protector to reach your gear. A surge protector regulates the current to connected equipment by either blocking or shorting to ground any "unsafe" voltage. Usually set up in a "strip" or box form, surge protectors have several power outlets to plug into. Better versions will also have at least one data outlet to protect a telephone, fax machine or modem as these are also in danger from a nasty surge of electricity through a phone line.
Why use it?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 worksHow 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 equipmentBlow 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?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.
Line noiseLine noise
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.
Why do we get power spikes and surges?Why do we get power spikes and surges?
The lower voltage surges that afflict modern household and business electrical wiring can come from many sources - internally and externally. External causes can include the startup or shutdown of nearby heavy equipment, fallen power lines, electrical storms, or even the normal "switching" of a nearby electrical substation. Internally, heavy equipment such as refrigerators and air-conditioners draw large amounts of current when switching on and off their motors/compressors. This creates surges through local electrical wiring -- a problem magnified when the wiring is also faulty. What is a line conditioner?
Line/power conditioners use a fairly simple system that relies on a built-in electromagnet to smooth out the small increases and decreases in current. This "conditioned" current is more stable, and therefore easier on your delicate equipment. Conditioners can also filter electromagnetic interference (EMI) from a power source and "smooth out" the rhythmic cycle of alternating current - this is called harmonic filtering. Harmonic voltage distortion can show up in various ways, such as increased heating of electrical components and cables, electronic miss-timings, capacitor overloads and fluorescent lights flickering.
Not a UPSNot a UPS
Note however, that a line conditioner will not provide battery backup power like an Uninterruptible Power Supply (UPS). A quality UPS should include both surge protection and power conditioning but with the added benefit of a battery backup and intelligent power management software for your PC to shutdown automatically and "safely".