During overloading and short circuits, we require circuit-breakers to safeguard electric circuits. Circuit-breakers are automatic devices capable of making and breaking of electric circuits. Insulating fluids are used here to extinguish the arc produced due to the fault current interruption and to provide total insulation between the contacts and from each contact to earth. Some examples of insulating fluids are air, compressed air, hydrogen producing oil and sulphur hexafluoride gas. Insulating materials used in circuit-breakers should have high dielectric strength, thermal and chemical stability, high thermal conductivity, low dissociation temperature, should be non-flammable, should not produce carbon during arcing and should be commercially available. The arc between the circuit-breaker consists of ionized gas particles. By deionizing, we can execute arc interruption. This can be done by high pressure development, arc splitting or forced convention and turbulence. Switchgear can be used to execute current interruption.
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