Why do transmission lines use two wires instead of one?

In summary, transmission lines use two wires instead of just one because it takes two lines to complete the circuit and allow the current to flow back to the source. This is similar to a loop of pipe with water, where a straight pipe with no exit results in no flow. While some transmission lines have used only one wire and an Earth return, this is not as efficient as using two wires. Overall, using two wires is the safer, more reliable, and more cost-effective option for transmission lines.
  • #1
fran1942
80
0
Hello, a beginners question here.
Can someone please tell me why transmission lines use two wires instead of just one ?
 
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  • #2
It takes two lines to complete the circuit. With only one line the current wouldn't be able to get back to the source, which is required in a circuit.
Think of a loop of pipe that contains water. If you put a pump in there the water goes round and round. If you do the same in a straight pipe that's capped off, the water has nowhere to go, and doesn't flow. A similar effect happens with electricity.
 
  • #3
Yes and no...

dont forget that there are were many transmission lines both power and communications
that used just 1 wire and an Earth return

Dave
 
  • #4
If you do the same in a straight pipe that's capped off, the water has nowhere to go, and doesn't flow. A similar effect happens with electricity.
 
  • #5
davenn said:
Yes and no...

dont forget that there are were many transmission lines both power and communications
that used just 1 wire and an Earth return

Dave

True. Per wiki on Single-Wire Earth Return:

SWER is a good choice for a distribution system when conventional return current wiring would cost more than SWER’s isolation transformers and small power losses. Power engineers experienced with both SWER and conventional power lines rate SWER as equally safe, more reliable, less costly, but with slightly lower efficiency than conventional lines.

So I would say that the 2nd wire completes the circuit because it is more efficient than using the Earth as the return.
 

Related to Why do transmission lines use two wires instead of one?

What is a transmission line?

A transmission line is a specialized type of electrical circuit that is used to transfer power or signals from one location to another. It is made up of two conductors that are separated by a dielectric material.

What are the types of transmission lines?

The two main types of transmission lines are balanced and unbalanced. Balanced lines have two conductors with equal currents flowing in opposite directions, while unbalanced lines have a single conductor with a return path through ground or a second conductor.

How do transmission lines work?

Transmission lines work by guiding electromagnetic waves, which carry the power or signals, along their length. The waves travel at the speed of light and are reflected at the ends of the line. The goal is to minimize the amount of reflection to ensure efficient transfer of power or signals.

What are the key parameters of transmission lines?

The key parameters of a transmission line are impedance, capacitance, and inductance. Impedance is the measure of resistance to current flow, while capacitance is the ability to store electric charge, and inductance is the ability to store energy in a magnetic field.

What are the applications of transmission lines?

Transmission lines are used in a variety of applications, including telecommunications, power distribution, and radio frequency systems. They are also commonly used in high-speed digital circuits to transfer data between components with minimal distortion.

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