How Surge Protectors Work
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Power surges occur when something boosts the electrical charge at some point in the power lines. This causes an increase in the electrical potential energy, which can increase the current flowing to your wall outlet. A number of different things can cause this to happen.
The most familiar source is probably lightning, though it's actually one of the least common causes. When lightning strikes near a power line, whether it's underground, in a building or running along poles, the electrical energy can boost electrical pressure by millions of volts. This causes an extremely large power surge that will overpower almost any surge protector. In a lightning storm, you should never rely on your surge protector to save your computer. The best protection is to unplug your computer.
A more common cause of power surges is the operation of high-power electrical devices, such as elevators, air conditioners and refrigerators. These high-powered pieces of equipment require a lot of energy to switch on and turn off components like compressors and motors. This switching creates sudden, brief demands for power, which upset the steady voltage flow in the electrical system. While these surges are nowhere near the intensity of a lightning surge, they can be severe enough to damage components, immediately or gradually, and they occur regularly in most building's electrical systems.
Other sources of power surges include faulty wiring, problems with the utility company's equipment, and downed power lines. The system of transformers and lines that brings electricity from a power generator to the outlets in our homes or offices is extraordinarily complex. There are dozens of possible points of failure, and many potential errors that can cause an uneven power flow. In today's system of electricity distribution, power surges are an unavoidable occurrence. In the next section, we'll see what this could mean to you.
You can also install a "whole-house" surge arrestor. You generally install these units near your electric meter, where the power lines run to your building. This protects all the circuits in your house or office from a certain range of voltage surges. Units designed for whole-house protection are generally built for outdoor installation. Better surge arrestors can handle surges up to 20,000 volts, while standard outlet surge protectors can't handle more than 6,000 volts. Some high-end arrestors can actually monitor weather conditions and will shut down the power supply to more sensitive electronics when lightning is in the area.
A whole-house surge protector will suppress power surges stemming from outside sources -- utility company problems, transformer switching, etc. -- but won't do anything to suppress the high number of power surges that originate inside your house, due to the operations of your appliances.
When to Use a Surge Protector
We have seen that power surges are a regular occurrence, unavoidable with our current system of providing electricity to homes and offices. This raises an interesting question: If power surges are an inherent part of our electrical system, why didn't we need surge protectors in our homes 50 years ago?
The answer is that a lot of the components in sophisticated modern electronic devices (such as computers, microwaves, DVD players) are much smaller and more delicate than components in older machines, and are therefore more sensitive to current increases. Microprocessors, which are an integral part of all computers as well as many home appliances, are particularly sensitive to surges. They only function properly when they receive stable current at the right voltage.
So whether or not you should get a surge protector depends on what sort of device you're hooking up to the power supply.
There's no reason to hook up a light bulb to a surge protector because the worst that is likely to happen due to a power surge is that your light bulb will burn out.
You should definitely use a surge protector with your computer. It is filled with voltage-sensitive components that a power surge could damage very easily. At the least, this damage will shorten the life of your computer, and it could very easily wipe out all of your saved data or destroy your system. Computers are very expensive items, and the data they hold is often irreplaceable, so it's only good economic sense to invest in a quality surge protector.
It's a good idea to use surge protectors for other high-end electronic equipment, such as entertainment center components. A surge protector will generally extend the life of these devices, and there's always a chance that a big power surge will causes severe damage.
One problem with surge protectors is that the MOVs can burn out with one good surge. This is why it's good to get a protector with an indicator light that tells you whether or not it's functioning properly.
Even if you connect surge protectors to all of your outlets, your equipment might be exposed to damaging surges from other sources. Telephone and cable lines can also conduct high voltage -- for full protection, you should also guard against surges from your telephone or cable lines. Any lines carrying signals into your home can also carry a power surge, due to lightning or a number of other factors. If your computer is connected to the phone lines via a modem, you should get a surge protector that has a phone-line input jack. If you have a coaxial cable line hooked up to expensive equipment, consider a cable surge protector. Surges on these lines can do just as much damage as surges over power lines.
Surge Protection Levels
This inexpensive, quality protector features basic MOV protection and line-conditioning systems.
All surge protectors are not created equal. In fact, there is a tremendous range in both performance and price of protection systems.
- At one end, you have your basic $5 surge protector power strip, which will offer very little protection.
- On the other end you have systems costing hundreds or even thousands of dollars, which will protect against pretty much everything short of lightning striking nearby.
Most systems have limitations of some sort; picking out a protector system that suits you is a matter of balancing the cost of the system with the cost of losing data or electronic equipment. As with insurance, you find the level of coverage you're comfortable with.
To protect your equipment from surges, you need individual surge protectors for each outlet. These power strips range a great deal in quality and capacity (as we'll see in the next section). There are three basic levels of power strip surge protectors:
- Basic power strip - These are basic extension cord units with five or six outlets. Generally, these models provide only basic protection.
- Better power strip - For $15 to $25 you can get a power strip surge protector with better ratings and extra features.
- Surge station - These large surge protectors fit under your computer or on the floor. They offer superior voltage protection and advanced line conditioning. Most models also have an input for a phone line, to protect your modem from power surges, and may feature built-in circuit breakers. You can get one of these units for as little $30, or you can spend upward of $100 for a more advanced model.
- Uninterruptable Power Supply (UPS) - Some units combine surge protection with a continuous UPS. The basic design of a continuous UPS is to convert AC power to DC power and store it on a battery. The UPS then converts the battery's DC power back to AC power and runs it to the AC outlets for your electronics. If the power goes out, your computer will continue to run, feeding off the stored battery power. This will give you a few minutes to save your work and shut down your computer. The conversion process also gets rid of most of the line noise coming from the AC outlet. These units tend to cost $150 or more.
An ordinary UPS WILL give you a high level of protection, but you should still use a surge protector. A UPS will stop most surges from reaching your computer, but it will probably suffer severe damage itself. It's a good idea to use a basic surge protector, if just to save your UPS.
Once you've decided what level of surge protection you need, it's time to shop around for a good unit.
Underwriters Laboratories Ratings
Shopping for a surge protector is tricky business because there are a lot of nearly worthless products on the market. Research into a particular model is the best way to ensure good results, but you can get a good idea of a product's performance level by looking for a few signs of quality.
First of all, look at price. As a general rule, don't expect much from any surge protector that costs less than $10. These units typically use simple, inexpensive MOVs with fairly limited capacities, and won't protect your system from bigger surges or spikes.
Of course, high price doesn't promise quality. To find out what the unit is capable of, you need to check out its Underwriters Laboratories (UL) ratings. UL is an independent, not-for-profit company that tests electric and electronic products for safety. If a protector doesn't have have a UL listing, it's probably junk; there's a good chance it doesn't have any protection components at all. If it does use MOVs, they may be of inferior quality. Cheaper MOVs can easily overheat, setting the entire surge protector on fire. This is actually a fairly common occurrence!
Many UL-listed products are also of inferior quality, of course, but you're at least guaranteed that they have some surge protection capabilities and meet a marginal safety standard. Be sure that the product is listed as a transient voltage surge suppressor. This means that it meets the criteria for UL 1449, UL's minimum performance standard for surge suppressors. There are a lot of power strips listed by UL that have no surge protection components at all. They are listed only for their performance as extension cords.
No surge protector is 100 percent effective, and even top of the line equipment may have some serious problems. Electronics experts are actually somewhat divided over the best way to deal with power surges, and different manufacturers claim other technologies are inherently faulty.
Surge Protector Ratings
A Belkin SurgeMaster II mid-range surge protector with connections for phone lines
On a listed surge protector, you should find a couple of ratings. Look for:
- Clamping voltage - This tells you what voltage will cause the MOVs to conduct electricity to the ground line. A lower clamping voltage indicates better protection. There are three levels of protection in the UL rating -- 330 V, 400 V and 500 V. Generally, a clamping voltage more than 400 V is too high.
- Energy absorption/dissipation - This rating, given in joules, tells you how much energy the surge protector can absorb before it fails. A higher number indicates greater protection. Look for a protector that is at least rated at 200 to 400 joules. For better protection, look for a rating of 600 joules or more.
- Response time - Surge protectors don't kick in immediately; there is a very slight delay as they respond to the power surge. A longer response time tells you that your computer (or other equipment) will be exposed to the surge for a greater amount of time. Look for a surge protector that responds in less than one nanosecond.
You should also look for a protector with an indicator light that tells you if the protection components are functioning. All MOVs will burn out after repeated power surges, but the protector will still function as a power strip. Without an indicator light, you have no way of knowing if your protector is still functioning properly.
If you're interested in learning more about these issues, and finding out all the ways surge protection technology can fail, check out some of the sites listed in the links section on the next page. Surprisingly, surge protectors are an extremely controversial piece of technology, and they have sparked a great deal of debate on the Web.