Hello guys, welcome to my blog. Hope you are good and well. 

Today we will discuss about, 

  • What is the corona effect in transmission? 
  • How corona effect occurs in transmission? 
  • Advantage and disadvantages of Corona? 
  • Factors on which corona effect depends?  
  • How to minimize corona effect?

Corona effect in electrical transmission
Fig. Corona effect in electrical transmission


We have discussed about types of insulators used in transmission and about layout of power system in our previous article. 



Now let's go to understand,

What is the corona effect on the transmission line: -


In high voltage transmission lines, a violet glow with a hissing sound is produced, this is known as corona effect. 

How corona effect occurs in transmission lines?


Let first understand about,

What is air breakdown?


When the voltage more than 33KV pass through 1 cm of air, the air starts to ionize known as breakdown of air. 

Ionize means air behaves as a conductor. 
( below 30KV/cm air acts as an insulator. )

Now understand how corona occurs?


When a high voltage (33KV or above) passes through a conductor, an electrostatic field is produced surround the conductor. 

(As we know that in a transmission line, three phase system is used due to which three conductors are used and placed near to each other in the air supported by the towers.)

Due to this electrostatic field produce surrounds the conductors in the transmission line air breakdown occurs means now air will also work as a conductor. 

And due to this air breakdown there is a violet glow occurs with a hissing sound along with the conductor. This violet glow with hissing sound is known as corona effect. 

Note: -

The electrostatic field strength will reduce with distance. Means more electrostatic field near to the conductor surface, but when we go far away from the conductor surface it starts to decrease. 

Advantages and disadvantages of the corona effect: -


Advantages: -


1. As due to breakdown of air, air also conducts and therefore the diameter of the conductor increase virtually.

So if the value of the current increase in the conductor due to any reason or fault the current will pass through this virtual conductor and protect the conductor from the damage. 

2. When a surge come on a conductor it may damage the conductor or electrical equipments used in substation. So due to corona effect these surges are used in corona losses. 

Surge means the voltage more than the normal working voltage. 

When these surges comes across the conductor due to any reason, the voltage of transmission line increase due to which the corona effect is also increased.

As this corona effect occurred in the form of light and heat energy so these surges are utilized in corona losses and protect the conductors as well as equipments. 

Disadvantages: -


1. Due to corona effect the power loss occurs in the transmission line in the form of light. 

2. The Corona effect produces ozone gas, which is a harmful gas.

3. As it produces ozone gas, which further produce an acid on the conductor surface. Due to this acid on conductor surface the conductor gets corrode. And the life of the conductor has reduced due to this corrosion. 

4. due to corona effect a sound is produced whose frequency is more which disturb the nearby communication circuits or lines. 

Factors on which corona effect depends: -


1. Atmosphere: - 


The corona effect depends upon the surrounding atmospheric conditions of the conductor. 

In the rainy seasons the corona effect will be more because the moisture content will available in the air, which will decrease the breakdown voltage of the air which will increase the corona effect. 


2. Conductors shape and size: -


The corona effect also depends upon the conductor shape and size. 

If the conductor is smooth and uniform, then the corona effect occurs along with the transmission line. And it will be more at joints and rough points.


3. Line voltage: -


The Corona effect occurs on high voltage transmission lines.

Higher the voltage more will be the corona effect and vice versa. 


4. Spacing between conductors: -


We can reduce the corona effect by increasing the distance between conductors. 

More will be the space less will be the corona effect. 

Methods of reducing corona effect: -


1. By increasing the cross sectional area of the conductor: -


The corona effect can be minimized by increasing the cross sectional area of the conductor. If the cross sectional area of conductor is more there will be a less corona effect. Therefore, in transmission lines, ACSR conductor is used which has more cross sectional area as compared to other type of conductor. 


2. By decreasing the line voltage: -


As corona effect occurs on high voltage so this effect can be minimized by reducing the transmission voltage level.

But in real practice, we don't reduce the voltage level because if we reduce the voltage level, then the cost of transmission will increase. 


3. By increasing the spacing between conductors: -


As we have studied above, we can decrease the corona effect by decreasing the distance between conductors. 

But in real practice, we don't do it. Because if we increase the distance between conductors then the distance between the tower cross arms will also increase, which further increase the cost of supporting structures. 

4. By using bundle conductor: -


We can also decrease the corona effect by using bundle conductors. Bundle conductors are nothing but two or more conductors used for one phase in the transmission. 


5. Anti-Corona ring: -


The corona effect can be minimized by using the anti corona ring. This is a smooth circular ring which takes the electric charge and discharge through it.

So we studied today about,

What is the corona effect in transmission?

How corona effect occurs in transmission?

Factors on which corona effect depends?

Advantage and disadvantages of corona effect?

How to minimize corona effect?

If you have any doubt then tell me in a comment. 

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Thank you.

Hope article helps you.