Arcing Phenomenon in Circuit Breaker:
When a fault occurs, a large current flows in a system and hence through circuit breaker connected in circuit. The circuit breaker is opened by protective system. At the instant when contacts just begin to separate, the face-to-face contact area between contacts reduces rapidly and the large fault current gets concentrated on reduced contact area. This causes very large current density at reduced contact area, which in turn rises temperature of contacts. With further movement of contact, the area again reduces, giving higher current densities and higher temperature rise. The heat produced due to very high temperature heats the surrounding medium and ionizes the medium. This ionized medium act as a conductor and establishes the current through separated contacts. This current through media due to ionization is called arc.
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