vacuum CBs
- 2. WHAT IS A CIRCUIT BREAKER? A circuit breaker is an equipment that breaks a circuit either manually or automatically under all conditions at no load, full load or short circuit.
- 3. Vacuum interrupters installed in indoor switchgear and kiosks rated up to 36 KV. Vacuum circuit breakers can be classified in the following two categories: Vacuum circuit breakers suitable for outdoor installation and having two or more interrupters in series per pole.
- 4. VACUUM CIRCUIT BREAKER • Vacuum is used as an arc quenching medium. • Have greatest insulating strength. • 10-7 to 10-5 pressure is to be maintained. • Used in 11KV panel in control room of grid station.
- 6. •When contacts of a breaker are opened ,Vacuum is being used as the arc quenching medium. •Vacuum offers highest insulating strength. •The interruption occurs at first current zero with dielectric strength between the contacts building up at a rate thousands of times that obtained with other circuit breakers. ABOUT CIRCUIT BREAKER
- 7. PRINCIPLE: •When the contacts of the breaker are opened in vacuum , an arc is produced between the contacts by the ionization of metal vapours of contacts. •The arc is quickly extinguished because the metallic vapours, electrons, and ions produced during arc condense quickly on the surfaces of the circuit breaker contacts, resulting in quick recovery of dielectric strength.
- 8. CONSTRUCTION: • It consists of fixed contact, moving contact and arc shield mounted inside a vacuum chamber. •The movable member is connected to the control mechanism by stainless steel bellows . •This enables the permanent sealing of the vacuum chamber so as to eliminate the possibility of leak . •A glass vessel or ceramic vessel is used as the outer insulating body
- 10. WORKING: •When the breaker operates the moving contacts separates from the fixed contacts and an arc is struck between the contacts. •The production of arc is due to the ionization of metal ions and depends very much upon the material of contacts. •The arc is quickly extinguished because the metallic vapours, electrons and ions produced during arc are diffused in short time and seized by the surfaces of moving and fixed members and shields.
- 11. WORKING: . •Vacuum Circuit Breaker in a vacuum breaker occurs with a short contact separation.
- 12. ADVANTAGES • Compact, reliable and have longer life. • No fire hazards. • No generation of gas during and after operation. • Can interrupt any fault current. • No noise is produced while operating. • Require less power for control operation.
- 13. DISADVANTAGES • It needs additional surge suppressors. • vacuum circuit breakers are uneconomical above 36kV. • Advance technology is used for production of vacuum interrupters.
- 14. APPLICATIONS: • For outdoor applications ranging from 22 kV to 66 kV. • Suitable for majority of applications in rural area.