Power surges, also know as transient voltage surges, are brief spikes of power that can permanently damage computers, televisions, fax machines and other home appliances that contain microprocessors and sensitive electronic components.
Surge suppressors can protect your equipment from voltage surges caused by unexpected occurrences such as a utility pole downed by a storm. Surges can also come from inside the home. Appliances such as furnaces, air conditioners and vacuum cleaners can cause power surges in your home electrical system when turned on or off. Remote lightning can also cause power surges. Underwriters’ Laboratory (UL) rated transient voltage surge suppressors can reduce the risk of such damage.
Some surge suppressors look very similar to multiple-outlet power strips but have the added feature of being able to suppress surges. Other surge suppressors resemble plug-in adaptors. Not all power strips and adapters, however, offer surge suppression so make sure the product and packaging clearly state that the product has a UL listed Transient Voltage Surge Suppressor. UL assesses surge suppressors for fire, electric shock and personal injury hazards and also categorizes the suppressors for how much voltage they can “clamp,” which prevents excess voltage from passing through to your electronic equipment. UL refers to this as a suppressed voltage rating with ranges from 330 volts to 4,000 volts.
Source: Underwriters’ Laboratory