Category: CIRCUIT BREAKERS

Circuit Breaker Ratings

Circuit Breaker Ratings: A Circuit Breaker Ratings may be called upon to operate under all conditions. However, major duties are imposed on the circuit breaker when there is a fault on the system in which it is connected. Under fault conditions, a circuit breaker is required to perform the following three duties : It must […]

Resistance Switching Circuit Breaker

Resistance Switching Circuit Breaker: We already know that current chopping, capacitive current breaking etc. give rise to severe voltage oscillations. These excessive voltage surges during circuit interruption can be prevented by the use of shunt resistance R connected across the circuit breaker contacts as shown in the equivalent circuit in Fig. 19.22. This is known […]

Switchgear Components in Circuit Breakers

Switchgear Components in Circuit Breakers: The following are some important components common to Switchgear Components in Circuit Breakers : Bushings Circuit breaker contacts Instrument transformers Bus-bars and conductors 1. Bushings: When a high voltage conductor passes through a metal sheet or frame which is at earth potential, the necessary insulation is provided in the form of […]

Vacuum Circuit Breakers

Vacuum Circuit Breakers (VCB): In Vacuum Circuit Breakers, vacuum (degree of vacuum being in the range from 10-7 to 10-5 torr) is used as the arc quenching medium. Since vacuum offers the highest insulating strength, it has far superior arc quenching properties than any other medium. For example, when contacts of a breaker are opened in […]

Sulphur Hexafluoride Circuit Breaker

Sulphur Hexafluoride Circuit Breaker: In Sulphur Hexafluoride Circuit Breaker (SF6) gas is used as the arc quenching medium. The SF6 is an electro-negative gas and has a strong tendency to absorb free electrons. The contacts of the breaker are opened in a high pressure flow of SF6 gas and an arc is struck between them. […]

Air Blast Circuit Breakers

Air Blast Circuit Breakers: These breakers employ a high pressure air-blast as an arc quenching medium. The contacts are opened in a flow of air-blast established by the opening of blast valve. The Air Blast Circuit Breakers cools the arc and sweeps away the arcing products to the atmosphere. This rapidly increases the dielectric strength […]