In overhead lines, this wire protects transmission line equipment from damage due to lightning surges.*Barbed WireGuy wireGuard wireEarth Wire

The wire that protects transmission line equipment from damage due to lightning surges in overhead lines is the Guard wire.

Here's a step-by-step explanation:

1. Overhead power lines are exposed to the environment, including lightning strikes.

2. To protect the transmission line equipment from lightning surges, a wire is installed above all the other wires on the transmission line.

3. This wire is known as the "Guard wire".

4. The guard wire is grounded, meaning it's connected to the earth at regular intervals.

5. When lightning strikes, it hits the guard wire first because it's the highest point.

6. The lightning surge is then directed to the ground, protecting the transmission line equipment from damage.