Correct Answer - Option 3 : Arced gas is poisonous
Concept:
- SF6 gas has excellent insulating property and it has a high electronegativity.
- Due to high electronegativity, the recovery of dielectric strength after the arc interruption in the SF6 circuit breaker is very fast.
- It has a high affinity for absorbing free electrons.
- It absorbs electrons from a negative ion. The attachment of electron with SF6 molecules may occur in two different reactions as shown below,
- Ions are obviously much heavier than a free electron and the overall mobility of charged particles in SF6 gas is much less compared to the other common gases.
Advantages of SF6 Circuit Breaker:
- High dielectric strength
- Take minimum time in installation
- The gas is non-inflammable and chemically stable; The decomposition products are non-explosive
- It gives noiseless operation it does not make a sound like an air-blast circuit breaker during operation
- Minimum maintenance
- The same gas is re-circulated into the circuit thereby reducing the requirement of SF6 gas.
Disadvantages of SF6 Circuit Breaker:
-
The SF6 gas is identified as a greenhouse gas, safety regulation is being introduced in many countries in order to prevent its release into the atmosphere.
- Puffer type design of SF6 CB needs high mechanical energy which is almost five times greater than that of the oil circuit breaker.
