# Voltage in the transmission line

In a power transmission line, the voltage at any point in the transmission line (along the length)is said to be the sum of the incident and reflected wave components of voltage. And if it is such then there should be some point in the transmission line where the voltage might be zero all the time. But the voltage is same throughout the line as the sending end voltage if losses are neglected Does it have to something with the wavelength?

• Does it have to something with the wavelength <-- have you researched this on google? Commented Jun 6 at 15:24
• Yes and came up with nothing.
– Jina
Commented Jun 6 at 18:48

And if it is such then there should be some point in the transmission line where the voltage might be zero all the time.

This is only true if

1. The wave is completely reflected from the end of the line.

2. The line is at least 1/4 wavelength long.

Or if the line termination is nearly a short-circuit, which would put the point of 0 voltage right at the termination, but would probably be fairly dangerous in a realistic power transmission system.

But the voltage is same throughout the line as the sending end voltage if losses are neglected

This is only true if the length of the line is much less than the wavelength (say, less than 1/10 or 1/20 wavelength).

Does it have to something with the wavelength?

Yes. The line can not at the same time be more than 1/4 wavelength long to allow for production of a perfect antinode in the standing wave, and also less than 1/20 wavelength long to produce nearly uniform voltage on the line.

Note that at 50 Hz, the wavelength is about 6000 km, so the situation of a "short" line (less than 300 km) is more common than a "long" line (more than 1500 km).

• Thank you for answering. So, since the wavelength of the standing wave (sum of incident and reflected wave) is very high for a 50 Hz system, the voltage is same at an instant of time (losses neglected) for a practical system(which is few hundreds of km long), isn't it? (Apologies for asking again just need some clarity, also can you suggest some materials from where I can refer this topic?)
– Jina
Commented Jun 6 at 18:45