A power surge is a temporary increase in voltage on a power line. Surges typically have less voltage than power spikes (usually 10% to 35% above the normal line voltage) but last much longer, from 15 milliseconds up to several minutes. Surges are common when power is supplied from lower quality generators. Sometimes surges are preceded or followed by spikes. Most modern power supplies can provide sufficient voltage regulation to protect equipment from everyday surges, but with very sensitive equipment and/or critical applications additional regulation is warranted. Voltage clamping devices such as spike protectors can help against some power surges, but this typically falls in the domain of something best handled by more of a voltage regulator.