CORONA - MU IMP NOTES (PSA/MU/SEM VI)

What is Corona?

So basically it's produced on transmission lines of hv side , producing hissing sound .

The envelope (sorroundig the hv side) is basically of ozone later.

In case of ac vs dc

Ac : the glow around the +ve as well as -chester is uniform because the + and - changes alternatively in ac , 

but in case of DC the + have a uniform glow but not in -ve conductor wire .

Disruptive critical vtg : it is a potential diff btw conductors at which the electric field intensity at the surface of conductor increase or exceeds from critcial vtg and Corona is generated.

Visual critical vtg: it is a region up to which there is no visual or glow of Corona on the hv side of transmission lines or can be said that 

If the potential gradient is below this region: no glow 

Above this region : glow will occur 

Note : it is for single as well as 3 phase lines.

Factors affecting Corona:

1. Atmospheric condition : take it rain for example when it touches the conductor more ionization takes place ,hence more will be Corona 
2. Frequency: directly prooptional to frequency 
3. air density: inversly proptional to air density , for instance , at hilly region air density is less ( u can't breathe right?) Corona will be more than the cornoa on Downer region ,where conductor is flat .
4. Air conductivity: higher air conductivity ,higher is the corona
5. Bundling of conductor: it reduces corona

Methods to reduce corona?

1.inc the length of conductor

2.not always inc option is available ,so increase the diameter instead of conductor 

Ex: use of hollow cylinder.

3.lower the vtg gradient .

4. Corona rings : it absorbs the electric field intensity and distribute the charge accrosee wider area , ex: toroids.

Advantage and diasdvantage of Corona :

   So till now u may be thinking it's fkin bad right? But wait it's not always the case , it has some great adv too:

Advantages: 

1.one is , due to Corona the the surrounding of the conductor also start conducting , can say as a virtual conductor itself 

2.flashover is reduced .

3.reduces electrostatic stress.

Transient due to surges are reduced .

Disadvantages:

1.When the corona is produced , the surrounding of the conductor lossed it's iron capability, ie. The corrosion increases.

2.transmission efficiency decreases.

3. Causes interference with radio signals.

Types of Corona : what? Yes there are also types lol 😂. 

1 .pulse free type : which only have enrgy loss.

2.pusle type : which have engergy loss + radio interference property which is not good.