Facts About Power Surges
What Are Power (Voltage) Surges?
A power surge is one form of electrical power disturbance. There are four main types of power
Power surges are generally considered to be the most destructive of the four types of electrical
Power surges are spikes in voltage. They are very brief, usually lasting millionths of a second.
Power surges can vary in duration and magnitude, varying from a few hundred volts to several
No matter where you live, your home experiences power surges.
How Does a Power Surge Cause Damage?
In the United States, most homes use electrical power in the form of 120-volt, 60 Hz, single
phase, alternating current. However, the voltage is not delivered at a constant 120-volts. With
alternating current the voltage rises and falls in a predetermined rhythm. The voltage oscillates
from 0 to a peak voltage of 169 volts.
Most appliances and electronics used in the United States
are designed to be powered by this form of generated electricity.
During a power surge, the voltage exceeds the peak voltage of 169 volts.
A spike in voltage can be harmful to appliances and electrical devices in your home. An increase
in voltage above an appliance’s normal operating voltage can cause an arc of electrical current
within the appliance. The heat generated in the arc causes damage to the electronic circuit
boards and other electrical components.
Smaller, repeated power surges may slowly damage your electronic equipment. Your computer
or stereo may continue to function after small surges occur until the integrity of the electronic
components finally erode and your satellite system, cordless phone, or answering machine
mysteriously stops working. Repeated, small power surges shorten the life of appliances and
Where Do Power Surges Come From?
There are several sources of power surges. They can originate from the electric utility company
during power grid switching. A common cause of power surges, especially the most powerful
ones, is lightning. Power surges can originate inside a home when large appliances like air
conditioners and refrigerator motors turn on and off.
_ Voltage dips (also called “sags” or “brownouts”)
_ Electromagnetic interference
_ Radio frequency interference
_ Power surges (also referred to as “voltage surges” or “transient voltages”)
There are over 20 million cloud-to-ground lightning strikes detected per year in the 48 contiguous
states of the US.1
Power surges can enter a home through several paths. In the case of lightning, it can take the
path of the cable TV or satellite dish cable, through the incoming telephone lines, or through the
incoming electrical service line.
Knowing that power surges can take several paths and do not have to enter through the electrical
panel indicates a good surge protection system should include:
When deciding on what type of and how much surge protection is needed, each house and its
contents should be assessed individually. An electrician knowledgeable about power surge
protection systems and the history of problems in your area is a valuable resource.