Spikes and transients are fast-moving, high-energy bursts lasting for just a few milliseconds that are superimposed onto the normal mains power supply.
They range from a few volts to several thousand volts (some can 6 kV or higher) and are caused by the sudden release of stored energy. Spikes and transients are common during electrical storms and following lightning strikes. They can also be caused by local load shedding and inductive motor loads such as lifts, escalators and fridge-freezers.
Spikes and transients differ to power surges because they are larger in magnitude yet much shorter in duration. These sudden bursts of energy can result in circuit board or processor damage, memory loss and data corruption.