The flow of electricity in a circuit sometimes gets interrupted, and when it starts again the power can surge, as electricity flows back into the system. The difference in voltage can vary from 5 to 10 volts or even thousands of volts when a transformer is struck by lightning.
Most power surges in homes are internal and can occur when devices start or stop, like motors in household equipment, and this diverts electricity from other devices in the home that are using electricity. The biggest problems are caused by power guzzlers like air conditioners, refrigerators, electric heaters and washing machines or dryers, whereas there may be minor surges when things like mixers or dryers are switched on. Power surges can also occur in a home, when the external source of power faces an interruption like branches of trees touching power lines, lightning strikes or even small animals touching terminals on a transformer. Power surges occur when power is restored after an outage of power, and can even enter homes through cable TV and telephone lines.
All electrical equipment is designed to work at particular voltages and when power surges occur they can disrupt their functioning. Instruments that contain microprocessors are especially vulnerable as even a small fluctuation in voltage can damage them or cause them to malfunction. The ill effects of power surges can be prevented by installing power surge protectors that guard the particular equipment from receiving more voltage than it is designed for. While these units can guard individual pieces of equipment it is also possible to
install power surge protection devices that can act as safety for the entire electrical circuits in a home.
Whole house surge protectors act as a form of insurance protection, so that all the equipment in your home is protected from any of the ill effects of power surges. The cost of installing such protectors must be balanced against the replacement cost of equipment that is damaged by power surges. These devices are best installed by qualified professional electricians, and need to be installed adjacent to the main electrical panel of the home. These devices will protect your electrical equipment from power surges coming from outside, but it makes sense to protect some very sensitive devices to extra individual protection, so that any power surges that occur within a home, by devices switching on and off, are also guarded against.
Devices that provide uninterrupted power to electrical items can also act as surge protectors, because they never allow the equipment to be starved of power, and ensure uninterrupted operations. This can be especially useful in computers that are connected to power mains. Most power surge protectors have a built in fuse and act to cut off power when the voltages in the power surge are very high. These protectors are rated in Joules, and those with higher Joule ratings will prevent higher surges. Most of this equipment is designed for the unit itself to fail when the power surges are beyond the rated capacity, and this cuts off the power supply and assures your attached circuit of complete protection.
Surge protection devices for the entire home are installed at the service entrance from where you get power, cable TV or telephone connections. This will protect all lights, switches, motors and any other systems that are hard wired to the mains supply. They however do not eliminate the damage that can be caused by internal power surges in a home. Most electrical systems have three wires ground, power and neutral and power surge systems must protect surges coming in on any one of these three wires.