Recovery Rate Theory and Energy Balance Theory
The rate at which the dielectric strength get recovered and then it is compared with the rate at which the restriking the voltage across the contacts rises.If the rate of rising of re-striking voltage is rapid than the dielectric strength then the space breaks down and arc persists.Since arc consist of column of ionized gases. So to extinguish the arc the ions and the electrons are required to be removed from the gap immediately after the current reaches to zero. It can be removed by recombining the ions and electrons with neutral molecules or by using the insulating medium in gap it can be swept away when the ions are removed from the gap with a rate faster than the rate of ionization then the arc get interrupted.
Energy balance theory:
Immediately after current zero the space between the contacts contains some ionized gas due to which it has a finite part zero resistance, at this moment power is equal to zero because re-striking voltage is equal to zero. The power again becomes zero when the arc is finally extinguished then the gap is demonized and resistance becomes infinitely high between these the first power increase having the maximum value then decreases and lastly reaches to zero.
Recovering and Re striking voltage:-
When the arc persist the voltage across the contacts in a circuit breaker it is known as arc voltage, as soon as the arc is extinguished the voltage becomes system voltage and this arc basically extinguished at a current zero. When this arc is extinguished the breaker terminal voltage does not normalized initially but oscillates creating a transient condition, this transient voltage is known as resting voltage.
When this transient oscillation die out after the arc is finally extinguished the power frequency rms voltage is created across the breaker contacts known as recovery voltage.
The process of cooling, stretching, or spreading out the arc within the spark gap so as to prevent the previously ionized path from reigniting on reapplication of voltage. It is mostly applied to AC power arcs and RF spark gaps, and also to high voltage DC switching. Quenching a high voltage arc needs the arc current passing through zero for a period of time. Which can be done using the normally occurring AC current zeros and also during brief current zeros.