The larger, more destructive surges, generally caused by lightning, can reach thousands of volts. Lightning doesn t have to strike the earth to cause damage. More common cloud to cloud strikes, even a mile away, can produce enormous magnetic fields that induce surges onto power, telephone and cable lines. Unchecked, such surges can quickly destroy wiring, appliances, telephones, and other electronic devices. Smaller surges may be caused by disturbances on the utility s transmission lines.
Proper grounding is the strongest prerequisite for proper surge protection.
Under normal conditions, MOVs offer high resistance to currents, preventing normal currents from discharging to ground. Surge strips, however, are not capable of suppressing a powerful surge, such as one caused by lightning, and most do not include any protection for telephone or coaxial cable lines. Although no product can protect a home against a direct lightning strike, the Institute of Electronics and Electrical Engineers recommends whole house surge suppression as the most effective way to protect against damage in the home. Whole house surge suppression devices protect the home where the electric, telephone, and cable lines enter the home. These devices serve as a first line of defense against surges and are installed directly at the circuit breaker panel or fuse box to protect all incoming lines.