Difference between Corona Discharge and Dielectric Breakdown?

[jaumzaum]

What's the difference between Corona Discharge and Dielectric Breakdown? For me both stand for the same process, but wikipedia (as many other sites) says they are different. Actually they say corona discharge occurs when the electric gradient is high but not enough to create an electrical breakdown. But I still do not understand the difference about them. Can anyone help me?

 

[Drakkith]

From wiki:

Thermodynamically, a corona is a very nonequilibrium process, creating a non-thermal plasma. The avalanche mechanism does not release enough energy to heat the gas in the corona region generally and ionize it, as occurs in an electric arc or spark. Only a small number of gas molecules take part in the electron avalanches and are ionized, having energies close to the ionization energy of 1 - 3 ev, the rest of the surrounding gas is close to ambient temperature.

I think this is the key. Not only is the plasma different, in a dielectric breakdown you would get a spark or arc from current flowing through the ionized plasma. This doesn't seem to happen in coronal discharge. The field strength isn't high enough to cause such a high amount of breakdown.

 

[lunaloca]

Hi there,

Yes,I agree with Drakkith. Corona discharge is a weakly ionised non-equilibrium plasma based on the avalanche mechanism. If it reaches close distance with a conductive material or you increase the electrical field, it can create longer breakdown streamers and eventually create sparks. Can you please explain what you mean by dielectric breakdown?

 

[voko]

In a dielectric breakdown, two conductors are connected by a well conducting channel made of ionized air. The current in that channel can be very high. In a corona, conductors are not connected by a well conducting channel, the charge is carried by a relatively small number of ions and electrons slowly diffusing through largely neutral gas. The current afforded by that transport is not very high.