Hardware Reference
In-Depth Information
Power-Protection Systems
Power-protection systems do just what the name implies: They protect your equipment from the
effects of power surges and power failures. In particular, power surges and spikes can damage
computer equipment, and a loss of power can result in lost data. In this section, you learn about the
four primary types of power-protection devices available and when you should use them.
Before considering any further levels of power protection, you should know that a quality power
supply already affords you a substantial amount of protection. High-end power supplies from the
vendors I recommend are designed to provide protection from higher-than-normal voltages and
currents, and they provide a limited amount of power-line noise filtering. Some of the inexpensive
aftermarket power supplies probably do not have this sort of protection. If you have an inexpensive
computer, further protecting your system might be wise.
Caution
All the power-protection features in this chapter and the protection features in the power
supply inside your computer require that the computer's AC power cable be connected to a
ground.
Many older homes do not have three-prong (grounded) outlets to accommodate grounded
devices.
Do not use a three-pronged adapter (that bypasses the three-prong requirement and enables you
to connect to a two-prong socket) to plug a surge suppressor, computer, or UPS into a two-
pronged outlet. They often don't provide a good ground and can inhibit the capabilities of your
power-protection devices.
You also should test your power sockets to ensure they are grounded. Sometimes outlets,
despite having three-prong sockets, are not connected to a ground wire; an inexpensive socket
tester (available at most hardware stores) can detect this condition.
Of course, the easiest form of protection is to turn off and unplug your computer equipment (including
your modem) when a thunderstorm is imminent. However, when this is not possible, other
alternatives are available.
Power supplies should stay within operating specifications and continue to run a system even if any of
these power line disturbances occur:
• Voltage drop to 80V for up to 2 seconds
• Voltage drop to 70V for up to .5 seconds
• Voltage surge of up to 143V for up to 1 second
Most high-quality power supplies (or the attached systems) will not be damaged by the following
occurrences:
• Full power outage
• Any voltage drop (brownout)
• A spike of up to 2,500V
To verify the levels of protection built into the existing power supply in a computer system, an
independent laboratory subjected several unprotected PC systems to various spikes and surges of up
