What is surge divertor?

Surge diverters are normally located on the terminal pole of an overhead line system, and are intended to protect terminal equipment (e.g. Transformers, cables, etc.) from sudden surges in voltage. Each of the line conductors is normally connected to earth, via the surge diverter.

Under normal circumstances, the internal resistance of the surge diverter is high enough to insulate the line conductor from earth. However, if a voltage surge occurs due, for example, to a lightning strike, then the resistance of the surge diverter will collapse, 'diverting' the surge to earth.