You can also install a "whole-house" surge arrestor. You generally install these units near your electric meter, where the power lines run to your building. This protects all the circuits in your house or office from a certain range of voltage surges. Units designed for whole-house protection are generally built for outdoor installation. Better surge arrestors can handle surges up to 20,000 volts, while standard outlet surge protectors can't handle more than 6,000 volts. Some high-end arrestors can actually monitor weather conditions and will shut down the power supply to more sensitive electronics when lightning is in the area.
A whole-house surge protector will suppress power surges stemming from outside sources -- utility company problems, transformer switching, etc. -- but won't do anything to suppress the high number of power surges that originate inside your house, due to the operations of your appliances.
Power surges occur when something boosts the electrical charge at some point in the power lines. This causes an increase in the electrical potential energy, which can increase the current flowing to your wall outlet. A number of different things can cause this to happen.
The most familiar source is probably lightning, though it's actually one of the least common causes. When lightning strikes near a power line, whether it's underground, in a building or running along poles, the electrical energy can boost electrical pressure by millions of volts. This causes an extremely large power surge that will overpower almost any surge protector. In a lightning storm, you should never rely on your surge protector to save your computer. The best protection is to unplug your computer.
A more common cause of power surges is the operation of high-power electrical devices, such as elevators, air conditioners and refrigerators. These high-powered pieces of equipment require a lot of energy to switch on and turn off components like compressors and motors. This switching creates sudden, brief demands for power, which upset the steady voltage flow in the electrical system. While these surges are nowhere near the intensity of a lightning surge, they can be severe enough to damage components, immediately or gradually, and they occur regularly in most building's electrical systems.
Other sources of power surges include faulty wiring, problems with the utility company's equipment, and downed power lines. The system of transformers and lines that brings electricity from a power generator to the outlets in our homes or offices is extraordinarily complex. There are dozens of possible points of failure, and many potential errors that can cause an uneven power flow. In today's system of electricity distribution, power surges are an unavoidable occurrence. In the next section, we'll see what this could mean to you.