High Voltage Protection of Electronics


A high-voltage surge on a power line can destroy electronics in a fraction of a second. Although a home or commercial power outlet typically delivers between 110 to 120 V, on rare occasions it briefly rises to thousands of volts -- far beyond the safe operating range for electronic equipment. You can protect your electronics with a variety of devices that prevent high-voltage energy from causing damage.

Voltage Surge

  • Because homes and businesses depend on reliable power, power companies strive to keep power line voltage tightly regulated; however, conditions such as lightning, bad wiring and the operation of industrial equipment are beyond the utilities' control. A lightning strike near a power transformer, for example, induces a pulse of electrical and magnetic energy in the equipment. In a few millionths of a second, the transformer undergoes a rise of thousands of volts, and the lines connected to the transformer carry this surge into homes and offices. Although a surge typically lasts only a few thousandths of a second, it carries enough energy to burn out sensitive electronic components.

Surge Suppressor

  • The lowest-cost option for high voltage protection of electronics is the surge suppressor, commonly found in power strips and other electronic equipment. The surge suppressor is a device called a Metal Oxide Varistor, a component that changes its electrical resistance in response to a sudden rise in voltage. Under normal conditions, the MOV has a high electrical resistance and plays no role in an electrical circuit. When the voltage exceeds a rated value, the MOV's resistance drops in a few trillionths of a second. Because current takes the path of least resistance, the MOV traps the surge and dissipates its energy. Although a severe surge will destroy an MOV, it is less expensive to replace than the electronic equipment it protects.


  • Constant Voltage Transformers regulate the voltage of the electric power passing through them. The CVT's input connects to a large-amperage power outlet; its output has standard AC outlets into which you plug your electronic equipment. Although more expensive than a surge suppressor, a CVT eliminates minor brownouts and other temporary voltage fluctuations in addition to blocking surges. A CVT makes sense when you need to protect expensive and electrically sensitive electronics.


  • An Uninterruptible Power Supply is a device that provides backup electricity when the main power fails. When the AC line voltage falls below a threshold value, such as 100 V, the UPS automatically turns the direct current, or DC, stored in an internal battery into 60-Hz AC, or alternating current, that's suitable for computers, medical electronics and other critical equipment. The UPS switches over rapidly, so the equipment keeps running without interruption. In addition to battery backup capability, a UPS protects against high-voltage surges.

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