AC Mains Transmission Tower question

In summary, the two smaller wires on the transmission towers are there to protect the line from lightning strikes and provide a fiber optic cable connection between the tower and the ground.
  • #1
phyzguy
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What are the extra two wires on the transmission towers.
Hi all. Many of you on the forum seem to be very knowledgeable on power transmission. I often notice transmission towers like this on. I know the three large wire groups are the three phases of the AC power, but the towers often have two smaller wires (red circle) on the top. Sometimes
they only have one. Does anyone know the function of these wires?
20220909_124249_resized.jpg
 
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  • #2
They are called shield wires. They protect the line from lightning strikes.
 
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  • #3
It is not clear to me how they work. Are the towers not grounded? Reference maybe?
 
  • #4
He said they protect the lines, not the towers. The towers are giant lighting rods anyway and are isolated from the lines. The lines of course can't be grounded...
 
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  • #5
Oh I missed the red circles. I thought there were lines lower down (they are on the background towers!). OK never mind. (But thanks!)
 
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  • #6
phyzguy said:
Summary: What are the extra two wires on the transmission towers.

Hi all. Many of you on the forum seem to be very knowledgeable on power transmission. I often notice transmission towers like this on. I know the three large wire groups are the three phases of the AC power, but the towers often have two smaller wires (red circle) on the top. Sometimes
they only have one. Does anyone know the function of these wires?
View attachment 314129
As others already said it's a ground wire that electrically connects every metal tower and serves as a "lightning rod" so that the bolt rather hits it first than any of the phases.

But since the 1980's it has also been used as a fiber optic cable. Most of these shield wires now are double purpose. The outer layer is metal strands that perform the shielding while inside there is a optical fiber cable for internet and communications.
It makes sense because fiber doesn't conduct so is immune from induced voltages and currents but it still passes light.

https://en.wikipedia.org/wiki/Optical_ground_wire
 
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hutchphd said:
It is not clear to me how they work. Are the towers not grounded? Reference maybe?
Towers are grounded, at least the ones I have seen all have ground bars that connect to one or more of the tower legs and run into ground/soil, but the upper shield wire connects each tower to the next, thereby I think it makes for a better ground and shield because not all towers stand on equally conductive ground.
 

Related to AC Mains Transmission Tower question

1. What is an AC Mains Transmission Tower?

An AC Mains Transmission Tower is a tall structure used to support high-voltage power lines for the transmission of electricity from power plants to substations and ultimately to homes and businesses.

2. How tall are AC Mains Transmission Towers?

The height of AC Mains Transmission Towers can vary, but they are typically between 100-200 feet tall. Some towers can reach heights of up to 500 feet.

3. How are AC Mains Transmission Towers built?

AC Mains Transmission Towers are typically constructed using steel or concrete. The tower is built in sections and then assembled on-site using cranes and other heavy equipment.

4. Why do AC Mains Transmission Towers have a lattice structure?

The lattice structure of AC Mains Transmission Towers allows for a strong and lightweight design that can withstand high winds and other environmental factors. It also allows for easy maintenance and repair of the power lines.

5. Are AC Mains Transmission Towers safe?

Yes, AC Mains Transmission Towers are designed and built to be safe. They are constructed to withstand extreme weather conditions and are regularly inspected and maintained to ensure their structural integrity.

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