Electricity is a funny thing. When it's flowing normally through the power lines and into our homes and electronic devices, it's wonderful. But, sometimes, that electricity can turn against us.
How? A lightning storm, a bird or animal hitting a power line or transformer, or a freak accident. Any of those incidents, and many others, can cause a power surge, which is a spike in the amount of electricity that's moving through the power lines into your home. A surge can bring with it anywhere from five to 10 times the normal amount of electricity.
As you've probably guessed, a power surge can play havoc with electronics like desktop computers, printers, televisions and audio systems. So much so that the surge can damage or destroy the delicate insides of those devices.
You can, however, prevent or minimize the damage done by power surges using a surge protector.
Surge protectors, and how they work
A surge protector (also called a surge suppressor or a power strip) diverts power away from your delicate electronics. You've probably seen one, or even own one: a white rectangular strip about a foot long, which plugs into a wall socket. On the strip are anywhere from six to eight sockets for your electronics, along with a power switch.
It's not what's on the outside that protects your devices. It's what's on the inside that really counts. A surge protector contains two lines: a main line that carries power from the wall socket to your devices, and a ground line that routes any excess voltage into the earth.
When a power surge hits, the surge connection – which links the main and ground lines – comes into play. A device within the surge protector, called a varistor (or a MOV), is what diverts the electricity. The varistor is a semiconductor made from metal oxide that has a variable resistance. When the voltage is at normal levels, the varistor doesn't conduct electricity very well. But when the voltage increases, the varistor becomes a very good conductor.
It's the varistor that shunts the excess electricity from a power surge from the main line to the ground line. Once the surge passes, the main line returns to normal.
Problems with surge protectors
There are a few. First, a power surge can carry a lot of electricity. The varistor in some surge protectors might not be able to handle all of that energy. It probably won't be able to if the surge lasts for more than a few fractions of a second. Some excess electricity may get to the device or devices that you're trying to protect.
No matter how good it is, a surge protector won't do its job at the exact moment a power surge hits. There's a short delay while the surge protector kicks in. During that interval, some excess electricity may hit your devices. With any luck the damage will be minimal, but you never can tell.
What to look for in a surge protector
When shopping for surge protectors, you really need to read the label (or the side of the box). That's where you'll find the information you need to make your choice.
Here are four things to look for when buying surge protectors:
First, the clamping voltage. This is the voltage at which the varistor will kick in. Common clamping voltages are 500 volts, 400 volts, and 330 volts. A surge protector with a clamping voltage of 400 volts or 330 volts will give you the best protection.
Second, consider the response time (also called the clamping response time). This is how quickly the varistor will kick in. Obviously, you want the fastest response time that you can get. Most surge protectors have a response time of a few nanoseconds (billionths of a second). That's pretty fast. But if you want better protection, go with a surge protector that has a response time of a few picoseconds (trillionths of a second).
Third, look at the energy absorption and dissipation rating of the surge protector. This is the amount of energy, measured in joules that the surge protector can handle before it's overloaded. Look for a protector with a minimum rating of 300 to 400 joules. A rating of 600 joules or higher will give you better protection.
Finally, remember the warranty. Things happen, and even really good surge protectors fail. Look for a surge protector with a lifetime warranty and which offers replacements for damaged or destroyed equipment.
As for brands, APC makes some of the best surge protectors on the market. Belkin's surge protectors vary in quality, but some of their higher-end models work very well. Dynex also offers some solid surge protectors for both your home office and home electronics.
You've probably spent quite a bit of money on the electronics in your home. A power surge can do nasty things to those devices. To protect your investment, try to buy the best surge protector that you can afford. If the worst happens, the price will be well worth what you paid.
This Tech Tip is brought to you by the Business and Technology Section ... IT solutions for today's CPAs. For more information and to view an archive of previous Tech Tips, please visit us here.
Do you have specific topics you would like to see covered in Tech Tips? Email any suggestions to firstname.lastname@example.org.
LAST UPDATED 6/16/2010