The subject of ‘Switchgear’ is regarded as protecting all types of switching units equivalent to circuit-breakers, contactors and hand-operated switches, in addition to fuses and protecting devices like relays. Vacuum Circuit Breaker (VCB) is one where vacuum of the order of 10-6 to 10-10 torr is used as an arc quenching medium. Larger circuit breakers akin to those used in electrical power distribution might use vacuum, an inert fuel akin to sulfur hexafluoride or have contacts immersed in oil to suppress the arc. Not like other circuit breakers, they constantly monitor all secondary circuits. After the ultimate arc interruption, there is quickly build up of dielectric power which is peculiar of the vacuum breaker. As the present in the solenoid increases beyond the ranking of the circuit breaker, the solenoid’s pull releases the latch which then allows the contacts to open by spring motion. This excessive dielectric energy makes it doable to quench a vacuum arc inside very small contact hole. Our circuit breakers are applied in panelboards, switchboards, motor control facilities, management panels, mixture starters, individual enclosures, and bus duct plug-in models. The vacuum circuit breaker consists of fixed contact, transferring contact and arc defend mounted contained in the vacuum chamber. Typical domestic panel circuit breakers are rated to interrupt 10 kA (ten thousand A) quick-circuit current. When an arc is opened by moving aside the contacts in a vacuum, an interruption occurs at the first present zero. A direct current circuit breaker could have blow-out coils which generate a magnetic area that quickly stretches the arc when interrupting direct current. When the contacts of the breaker are opened in vacuum (10^-7 to 10^-5 torr), an arc is produced between the contacts by the ionisation of steel vapours of contacts. The introduction of the chrome copper contacts brought a discount of the chopping present to between 2 to chance of impermissible over voltages arising attributable to current chopping has been lowered to a negligible stage. Table 1. Traits of the SF6 and vacuum current interrupting applied sciences. Vacuum circuit breaker memiliki ruang hampa udara untuk memadamkan busur api, pada saat circuit breaker terbuka (open), sehingga dapat mengisolir hubungan setelah bunga api terjadi, akibat gangguan atau sengaja dilepas. The number of defective tripping occurred in whole life span of circuit breaker typically depends upon the location of the system, quality of atmosphere situation and system. Below short-circuit conditions, the calculated or measured most prospective brief-circuit present may be many times the normal, rated present of the circuit. This is because of the truth that at high voltages (above 38 kV) greater than two numbers of the circuit breaker are required to be linked in collection. As the present in the solenoid increases past the ranking of the circuit breaker, the solenoid’s pull releases the latch, which lets the contacts open by spring motion. At the moment it’s accepted that an oxygen free copper chromium alloy is the most effective material for High voltage circuit breaker. Miniature and molded case circuit breakers are normally discarded when the contacts are worn, however energy circuit breakers and excessive-voltage circuit breakers have replaceable contacts. The characteristics of MV breakers are given by international requirements comparable to IEC 62271 Medium-voltage circuit breakers nearly at all times use separate current sensors andprotective relays, as a substitute of counting on constructed-in thermal or magnetic overcurrent sensors. High-voltage AC circuit breakers are routinely out there with ratings as much as 765,000 volts. Low voltage circuit breakers are basically the protection in opposition to overloading, short circuits and earth leakage while medium voltage circuit breakers provide centralized control and safety for medium voltage power gear and circuitry in business and industrial installations together with transmission and distribution lines. These new kinds of breakers are cumbersome and cumbersome. In this method, the vacuum circuit breaker prevents the restoration of the arc by producing a high dielectric energy within the contact area after the current zero.