Power surges from lightning, grid switching, and motor startups damage equipment across residential and commercial facilities without warning. A voltage surge protector is an electrical product for over-voltage protection. It reacts to transients, blocking or transferring the excess energy to the ground. That way, it prevents surges from causing damage.

A surge may emanate from a lightning strike near power lines. It may also result from heavy loads, such as industrial motors, switching on and off. Other causes include grid outages and faults in the wiring.