In New Zealand the effective AC utility voltage is 240 volts. Transients, which arise from various causes, commonly reach peak levels of several hundred volts more. These pulses are of short duration, measured in microseconds, but in that time, they can cause hardware to malfunction or data to get scrambled. The worst type of transient occurs when lightning strikes nearby (it is not necessary for a power line to be directly hit). Such a "spike" can peak at thousands of volts and cause permanent damage to equipment.

A surge suppressor prevents the peak AC voltage from going above a certain point. The power line is effectively short-circuited to electrical ground for transient pulses exceeding the threshold, while the flow of normal 60-Hz current is unaffected. For the suppressor to work, a 3-wire AC power connection must be used. "Cheater" adapters, which allow 3-wire appliances to be used with 2-wire outlets or extension cords, defeat the electrical ground connection and render most surge suppressors ineffective.

Surge suppressors should be used as a matter of habit with electronic and computer hardware, including peripherals such as printers, monitors, external disk drives, and modems. However, the suppressor should not be relied upon to provide protection against lightning-induced transients. The safest procedure, inconvenient though it be, is to ensure that all susceptible hardware is plugged into the suppressor box, and to unplug the suppressor's main power cord and data (phone) cord when the equipment is not in use if you live in a thunderstorm-prone area.

Some Quick Facts and Figures on Lightning

• Each lightning strike is composed of a number of surges ranging from two and as many 20 or 30 surges.
• Average duration of peak current in a lightning discharge: 1/1000 sec.
• There are 100 flashes of lightning per second on earth

Everyone in the country has had problems with their weather at some point and time. Computers must be protected with a Surge Protector or UPS to survive today’s power disruptions.

Next Week: Surge Protectors vs UPS