Voltage spike

Fast, short duration electrical transients (overvoltages) in the electric potential of a circuit are typically caused by[2] In the design of critical infrastructure and military hardware, one concern is of pulses produced by nuclear explosions, whose nuclear electromagnetic pulses distribute large energies in frequencies from 1 kHz into the gigahertz range through the atmosphere.

In semiconductor junctions, excessive electric current may destroy or severely weaken that device.

[3] Voltage spikes, also known as surges, may be created by a rapid buildup or decay of a magnetic field, which may induce energy into the associated circuit.

However voltage spikes can also have more mundane causes such as a fault in a transformer or higher-voltage (primary circuit) power wires falling onto lower-voltage (secondary circuit) power wires as a result of accident or storm damage.

Power increases or decreases which last multiple cycles are called swells or sags, respectively.