In the overhead transmission line, the ground wire is above the phase lines. Why?

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     The ground wire in an overhead transmission line is positioned above the phase conductors (i.e. the power lines) because it serves as a protective shield against lightning strikes. When a lightning strike occurs, the current from the strike travels through the ground wire, which is connected to the earth at each tower in the transmission system. This helps to dissipate the energy of the lightning strike into the ground and prevent it from affecting the phase conductors below.

     The ground wire is typically made of steel because it does not need to conduct electricity, but rather just serves as a path for the lightning current to follow. In high voltage transmission lines, ground wires are often used in pairs for improved protection. The use of multiple ground wires can help to reduce the coupling effect of lightning surges, which can cause voltage spikes on the transmission line.

     In addition to the ground wire, other measures are also taken to protect overhead transmission lines from lightning strikes. These may include deep grounding rods or counterpoise wires, which are used to minimize the chances of fault due to flash-over of insulators on the towers. Proper grounding and earthing of the poles and towers is essential for effective protection against lightning strikes.

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