A lightning arrester protects telecommunication and electrical power systems from damage during a lightning strike. It accomplishes this by redirecting the current in the lightning to the ground.
Lightning is caused by the movement of a large current from a region of high voltage to a region of low voltage. Lightning finds the path of least resistance to reach the ground. Telecommunications towers and electrical grids provide a path for lightning to travel, but the high voltage of the lightning can damage the components of the system. Adding a lightning arrester to the system redirects the charges in the lightning to the ground. One terminal of the arrester is connected to the device and the other terminal is connected to a rod or wire of low resistance that is buried in the ground. Between the two terminals is a gap of either air or a material of high resistance. This material prevents the normal signals from the telecommunication device from being redirected to the ground. Since lightning strikes have a high voltage, only the electrons from the lightning can cross the region of high resistance, thus diverting the strike away from sensitive devices such as televisions, radios and other telecommunications technology.