An overhead line earth wire, also known as a shield wire or static wire, is a conductor installed at the very top of an overhead transmission tower, positioned above the phase conductors. Its primary purpose is to provide lightning protection for the transmission line. When lightning strikes the overhead line, it will most likely hit the highest point, which is the earth wire. The earth wire is grounded at each tower, providing a low-resistance path for the lightning's high current to safely dissipate into the ground, thus protecting the energized phase conductors below from a direct strike. This helps prevent power outages and damage to expensive equipment.