Why is the Ground Wire Always Positioned Above the Overhead Power Lines?
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:
Lightning Protection
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.
Visual Marker
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.
FAQ
Why ground wire is placed at the top of the pole?
Ground wires
The ground conductor is usually grounded (earthed) at the top of the supporting structure, to minimize the likelihood of direct lightning strikes to the phase conductors. In circuits with earthed neutral, it also serves as a parallel path with the earth for fault currents
Why do power lines need to be above ground?
The electric utilities will likely say that power lines are above ground because they are easier to repair and maintain. They will likely fail to mention it is also cheaper for them. Even though having power lines underground would save lives and protect equipment, the utilities do not want to make the investment
What is the wire placed on the top of a transmission line?
guard wire – Detailed Solution. A guard wire or earth wire is the topmost conductor in high voltage transmission lines. It is used mainly to protect lines from lightning. If in case lightning struck then it carries the excessive current inrush to the ground
What is the purpose of overhead ground wires?
Ground wires or earth wires are bare conductors supported at the top of transmission towers. They serve to shield the line and intercept lightning stroke before it hits the current carrying conductors below i.e. power lines
Why is the ground plug on top?
With the ground up, if the plug should work its way loose you have the ground prong on top to protect an object from falling across the hot and neutral prong. If the ground is down and the plug works it way loose the item that is plugged in is still grounded protecting the user
Where is the proper ground rod placement?
Picking a Location for the Rod
Make sure the spot is convenient to get to and has enough space for you to use tools to drive the rod into the ground. Keep the ground rod at least 2 feet (0.61 m) from the side of your house. This prevents the ground rod from hitting the foundation
Why are power lines above ground in Japan?
After World War II power lines were installed aboveground in Japan to save time as the nation eyed a quick recovery, even though gas and water lines remained underground. Since the 1970s, there have been increasing calls to move power lines underground, partly to improve scenery
Why do transmission lines have 3 wires?
As compared to a single-phase AC power supply that uses two current-carrying conductors (phase and neutral), a three-phase supply with no neutral and the same phase-to-ground voltage and current capacity per phase can transmit three times as much power by using just 1.5 times as many wires (i.e., three instead of two)
Why is the overhead transmission line the ground wire above the phase line?
By positioning the ground wire above the phase line, it helps intercept and conduct lightning currents safely to the ground, protecting the phase conductors from damage. This arrangement helps to reduce the risk of overvoltages and flashovers during lightning events
