A lightning arrester is a device used on electrical power systems and telecommunications systems to protect the insulation and conductors of the system from the damaging effects of lightning. The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth.
Lightning arresters, or surge arresters, since in this case the terms are somewhat interchangeable, are a device that is installed to protect homes, structures, and power lines from dangerous surges of power. As you might expect, the primary defense is against lightning and the damage it can cause, however residential surge arresters also provide defense against surges from other sources as well.
The device which is used for the protection of the equipment at the substations against travelling waves, such type of device is called lightning arrester or surge diverter. In other words, lightning arrester diverts the abnormals high voltage to the ground without affecting the continuity of supply. It is connected between the line and earth, i.e., in parallel with the equipment to be protected at the substation.