Switchgear & Protection | State methods for arc extinction and explain working of any one method with neat circuit diagram.

Methods for Arc Extinction:

There are two methods of arc extinction: 

i) High resistance extinction method

ii) Low resistance or Zero current extinction method

High Resistance Arc Extinction Method:

In this method, the arc is so controlled that its effective resistance increases with time so that the current reduces to a value insufficient to maintain the arc. The currents tends to be in phase with the voltage so that at zero current instant, the restriking voltage appearing across the contacts is relatively low and arc cannot struck again. Arc path resistance is increased to reduce the current to low values while interrupting the arc. 

Arc resistance = v arc /i arc. The arc resistance mainly increased by:

i) Lengthening of the arc by arc  runners

ii) Splitting the arc by arc splitters: An appreciable voltage is absorbed at the contact  surface so that if the arc can be split into a number of small arcs in series, the voltage available for the actual arc column is reduced. 

iii) Arc cooling: The voltage required to maintain ionization increases with decrease of temperature of arc, so that cooling effectively increases the resistance. 

iv) Constraining the arc: If the arc can be constrained into a very narrow channel, the voltage necessary to maintain it is increased.