Lightning Arrester :

According to most definitions, a Lightning Arrester is a Device Used on Power Systems above 1000V to Protect other Equipment from Lightning and Switching Surges.It is not a Lightning Rod. Although Lightning Rods are devices that divert lightning surges to ground, they are simple conductive terminals that are always at ground potential and are never energized.Other Devices Similar to Lightning Arrester are Surge Suppressor: This is also a surge diverter, but generally for voltages well below 1000 volts.TVSS(Transient Voltage Surge Suppressor) Again this is also a surge diverter, but generally for voltages well below 1000 volts.

How do Lightning Arrester Protect Power Systems?

When Lightning strikes the system equipment is damaged and the lights go out.However on a System With an Arrester When Lightning strikes Sensitive equipment is saved by the Arrester.

What exactly does a Lightning Arrester do?
•It Does not Absorb the Lightning
•It Does not Stop the Lightning
•It Does Divertthe Lightning to Ground
•It Does Clamp (limit) the Voltage produced by the Lightning
•It Only protects equipment electrically in parallel with it.

How does it divert lightning?

To Power System conductor. At the Heart of All Arresters is the Metal Oxide Varistor (MOV). The MOV Disk is a Semiconductor that is sensitive to Voltage. At normal Voltages the MOV disk is an insulator and will not conduct current. But at higher voltages caused by lightning it becomes a conductor.A lightning Arrester is essentially a collection of billions of microscopic junctions of Metal Oxide Grains that turn on and off in microseconds to form a current path from the top terminal to the ground terminal of the arrester.So there you have it. A Lightning Arrester is a device, used on power systems, that contains billions of electronic switches that divert lightning around sensitive equipment and saves them from damage.