This is a short term (transient) condition causing a larger than normal amount of voltage to be applied to a circuit. Voltage spikes can often cause damage to an electric device if it is not properly protected.

Voltage spikes are fast, short duration electrical transients (overvoltages) in the electric potential of an circuit. These are typically caused by lightning strikes, although power outages, tripped circuit breakers, short circuits, power transitions in other large equipment on the same power line, and malfunctions caused by the power company can also cause them. Other transients can be created by an electromagnetic pulse (EMP) with electromagnetic energy distributed typically up to the 100 Khz and 1 Mhz frequency range.