What’s a surge?
The power you get from the wall outlet is known as “120 volts AC power.” It can be represented by a sine wave of voltage, as shown. The power companies try to keep that voltage uniform. Lightning, short-circuits, poles knocked down by cars, or some other accident can make the voltage jump to hundreds, even thousands of volts.
The voltage spike shown is what engineers call a “surge.” A surge will last only a few millionths of one second (the “blink of an eye” is thousands of times longer than the typical surge). It is enough to destroy or to upset your appliances.
What can a surge do to your appliances?
Your appliances are designed to run on the normal 120 volts AC supply, with some tolerance for more or less, but they can be damaged, or their controls can be upset by surges. The result is then frustration and repair bills, and even a fire in rare cases.
See the next section for a discussion of how sensitive your appliances can be to these surges.
Don’t give up!
You can do something about it, your electrician can help and even the power company can offer help, as this booklet will show you -the why’s and how’s.
Other disturbances. . .
. . . and what they can do to your appliances
In the normal operation of a power system, unavoidable disturbances other than surges also happen. They can upset electronic appliances, but are unlikely to cause permanent damage. This booklet is concerned with surges and how to protect your appliances against surges. However, just to give you an idea of what these other disturbances can be, the graphs and words below will give you the right words when you want to discuss a problem with your power company, your electrician, and (hopefully, not any longer) an electronics repair shop.
Normal – This is the voltage that we all take for granted, every second of the minute, every minute of the hour, every hour of the day, every day of the year. But occasionally, for a short time…
The voltage falls below normal: a sag. Sags are unlikely to damage most appliances, but they can make a computer crash, confuse some digital clocks and cause VCRs to forget their settings.
The reverse of a sag is called a swell: a short duration increase in the line voltage. This disturbance might upset sensitive appliances, and damage them if it is a very large or very long swell.
Noise is a catch word sometimes used to describe very small and persistent disturbances. These do not have damaging effects but can be a nuisance.
There is, of course, the ultimate disturbance: an outage -no voltage at all!
These disturbances are different from surges, but they should be mentioned because the remedies are generally different. As we will see later, some available devices can help overcome both.