Surge arrestors - by Intermatic
Lightning and fluctuations in utility power (caused by grid switching, for example) are often assumed to be the main sources of power disturbances. However, the overwhelming cause is actually equipment, such as motors and appliances, turning on and off. Even simply switching lights on and off will cause electrical surges. In fact, it is estimated that 65% of all transient voltage surges are generated from inside sources, while only 35% come from outside.
Utility industry experts estimate that problems resulting from transient voltage surges cost U.S. companies a stunning $26 billion annually. This figure not only includes the high price of direct damage to electrical distribution systems, electronic equipment and microprocessor controllers, but also the crippling cost of lost productivity. This means that minimizing the risk of damage from electrical surges is an absolute priority for companies of all types, all across the globe.
A surge arrester acts like a trapdoor to excess electrical energy. Sometimes called over-voltages, or transients, or surges, unwanted bursts of electricity are lured to the trapdoor by what is called a low-impedance path to ground. The trapdoor is a metal oxide varistor, or MOV, which opens or "clamps" when the overvoltage exceeds a certain level, and safely diverts most of the excess energy to the ground rod.
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