A power surge is a transient voltage spike in a power or data line. The most familiar cause is lightning strikes, but this is actually just one of several common causes.
More frequent causes include the switching on and off of high-powered machinery, such as elevator motors or air conditioners. The resulting changes in magnetic or electrical fields around these high-power lines can lead to voltage transients in surrounding cabling.
Surges can also occur as a result of faulty equipment or downed power lines. In today’s complex power distribution system, this kind of event should be considered inevitable.
As electronic equipment gets ever more compact, the modern, delicate components contained therein become increasingly sensitive to excessive variations in current and voltage. If a sufficiently powerful transient enters the equipment, it may become irrevocably damaged and even catch fire.