Why is the Ground Wire Above the Phase Lines in the Overhead Transmission Line?
The ground wire (also known as earth wire or OPGW) above the phase lines in overhead transmission lines primarily serves as a protective and safety measure, providing lightning protection, ground fault protection, and helping to prevent disruptions to the electrical system.
In overhead transmission lines, the positioning of the ground wire above the phase lines serves a specific purpose related to the safety and performance of the electrical distribution system. This configuration is typically known as a “shield wire” or “static wire,” and it has several important functions as follows:
One of the primary purposes of the ground wire being above the phase lines is to provide lightning protection to the overhead power transmissions lines. Lightning is a natural phenomenon that can strike tall structures like transmission towers.
By placing the earth wire above the phase conductors, It intercepts and safely carries lightning strikes to the ground through the transmission towers and grounding system, keeping them away from the phase conductors. This reduces the risk of damage or power interruptions caused by lightning strikes.
Ground Fault Protection
The ground wire, which is grounded at intervals, helps to maintain the electrical system’s integrity by providing a low-resistance path to the ground. This is important for quickly diverting fault currents to the ground in the event of a ground fault. By positioning the ground wire above the phase conductors, it minimizes the risk of phase-to-ground faults that can disrupt the system.
Protecting Against Wildlife Contact
Overhead transmission lines are at risk of wildlife coming into contact with the conductors. Placing the ground wire above the phase lines can act as a deterrent to birds and other animals that might otherwise land on the conductors and create potential faults.
The ground or earth wire, often colored brightly and easily visible, serves as a visual marker for aircraft, helping to prevent collisions with the transmission lines.
Good to know: Ground wire above the overhead power lines serves as a communication cable known as Optical Ground Wire (OPGW). The optical fiber composite overhead grounding wire is used for both communications and grounding purposes.
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