Overhead Ground Wire for Lightning Protection
A transmission ground wire hangs above power and data transmission cables. These static shields are so valuable that most electrical transmission and distribution systems use two overhead ground wires instead of one. In addition, static shields have a steel core. Since they only carry energy when struck by lightning, steel is a great material for these wires.
When lightning strikes, it hits the overhead electrical wire instead of the transmission cables below. The energy enters the steel core of the static shield and travels along the wire. Like transmission lines, the ground wire stretches between utility poles and support towers. At each structure, the wire discharges energy through grounding. Safely directed into the ground, the lightning's energy cannot damage the power line.
Without a static shield, lightning strikes cause a surge in the amount of energy in the transmission cables. Those high voltages can create flashovers between support towers.