Why humming sound in transmission line?


Friends, whenever you go near the transmission line, you hear sounds like zi.. zi.. zi… In technical language, this sound is called humming sound. Friends, now the question comes to everyone’s mind why does the humming sound come in the transmission line?

You must remember that the hissing sound is also called the humming sound in many places. Now understand what the reason behind the humming sound is.

Why Humming in Transmission line?

If we talk in starting of the post that why does the humming sound come? The reason for the humming sound is the corona effect. Some people say only purple light is seen around the transmission line due to the corona effect. transmission line corona effect
So friends, due to the corona effect, not only purple color light but these three effects are also produced:
  1. Violet Glow
  2. Hissing Sound
  3. Ozone

So you should always keep these three points in mind whenever an exam or interviewers ask what effect occurs due to corona. Then you can tell these three points produced due to the corona effect.

What is Corona Effect?

Friends, high voltage passes through the transmission line, and the transmission line is hung in the air with the help of a steel tower. We think that there is no current flow inside the air.

But friends, this is not true. Air is not a pure insulator, which means that current can flow through the air. Corona effect is the flow of current through the air or ionization of the air.

Now you will say that when this situation arises, that current starts flowing through the air?

corona effect in hindi »

So to find this, we need to know the dielectric strength of air. Dielectric strength means how much maximum voltage we can apply so that our air will remain normal or it will not ionize.

Now people will say, what is the meaning of ionizing? So let us understand the importance of ionizing once, then further, we will understand the corona effect further.

What is ionization?

So friends, the simple meaning of air ionization is that when current flows through a conductor, it starts flowing through the air around it. Friends, every insulator has a dielectric strength. If we give more voltage than its strength, then current starts flowing through that insulator.


For example, the dielectric strength of air is 30KV/cm. If 30KV is supplied in a line, then the current will start flowing around that wire. And as we increase the voltage, the area of ​​​​air current flow also increases.

Note: Critical voltage is the maximum voltage level. After that, in increasing voltage, Air breakdown will start.

Air breakdown means that the current starts flow in the air. Humming sound comes in the transmission line due to air breakdown.


Friends, if you are asked this question in the interview, then there is no need to tell all this.

You have to answer simply that the humming sound comes in the transmission line due to the corona effect. Now, if you are further asked why the humming sound comes from the corona effect.

So you can say that our air is not a pure insulator. It has a dielectric strength. If we connect a higher voltage than the critical voltage, which is 30KV/cm, then there will be a breakdown of the air.

With the breakdown of the air, current starts to flow in the air. So due to this, we hear the humming sound from our transmission line. Along with this, vibration is generated in the conductor and purple-colored light is seen around the conductor.
Note: Violet light is not always visible. It will be visible only when the corona effect is high, or it is rainy season.

So friends, we hope that in today’s post, you have got the answers to all the questions related to the corona effect and the humming sound of the transmission line.

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Thank You 🙂

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Aayush Sharma is an Assistant Engineer in a Semi-Government Company and Owner of "Engineering Dost" and the Electrical Dost YouTube Channel. He Provides you Engineering inquiry and support of engineering market facts with Practical experience.


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