Methods of Arc Extinction in Circuit Breaker

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Methods of Arc Extinction in Circuit Breaker


As long as this arc is sustained in between the contacts the current through the circuit breaker will not be interrupted finally as because arc is itself a conductive path of electricity. For total interruption of current the circuit breaker it is essential to quench the arc as quick as possible.

  • The main designing criteria of a circuit breaker is to provide appropriate technology of arc quenching in circuit breaker to fulfill quick and safe current interruption.

Methods of Arc Extinction in Circuit Breaker

There are two methods of extinguishing the’arc in circuit breakers

1) High resistance method

In high resistance method, the arc resistance is made to increase gradually with the time so that the current force in between the two contacts is insufficient to maintain the arc. Hence the current is interrupted by with high resistance the arc is extinguished without creating any damage to the circuit breaker compartment.

  • The major work is to increase the resistance for the arc current. The following are the different ways to increase the resistance of the arc medium.

1. Reducing X-section of the arc – If the area of X-section of the arc is reduced, the voltage necessary to maintain the arc is increased. In other words, the resistance of the arc path is increased. The cross-section of the arc can be reduced by letting the arc pass through a narrow opening or by having smaller area of contacts.

2. Splitting the arc – The resistance of the arc can be increased by splitting the arc into a number of smaller arcs in series. Each one of these arcs experiences the effect of lengthening and cooling. The arc may be split by introducing some conducting plates between the contacts.
Lengthening the arc – The resistance of the arc is directly proportional to its length. The length of the arc can be increased by increasing the gap between contacts.

Arc Extinction in Circuit Breaker3. Arc Cooling method – Cooling arc medium helps in deionization of the medium which carries the arc current. This intern increases the arc resistance which prevents the arc to persist. Effective cooling may be the blasting type which forces the cooling element along the arc.

4. Increase the length of the arc – The resistance of the wire or any conductor can be increased by increasing the length of it. Here also the air (gap between conductors) acts as conductor so that by increasing the gap between the contacts then the resistance of the arc can be increased. I.e. the resistance of the arc is directly proportional to the length of the arc.

2)  Zero Current method.

  • This method is applicable only in AC circuit interruption because there are natural zero of current, 100 times in a second for 50Hz three-phase supply system.
  • This is one of the most significant advantages of AC circuit for arc interruption purpose because the current is not allowed to rise again.

Arc Extinction in Circuit Breaker - zero current method

In this method, the arc resistance is kept low until the current is zero where the arc extinguishes naturally, and it’s prevented from re-striking after it has gone out at a particular

  1. high pressure.

If the pressure in the vicinity of the arc, is increased, the density of the particles constituting the’ discharge also increases. The increased density of particles causes higher rate of de-ionisation and consequently the dielectric strength of the medium between contacts is increased.

2. Blast effect of ions

This is one of the best ways. In this method the ionized particles in the arc chamber are swept way at zero current point and replaces with the new ones, so these new particles offers high dielectric strength in between the circuit breaker contacts.

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