Electrical Engineering MCQs on Power System Protection
Breaking capacity of SF6 circuit breaker is not affected by:
- Pollution
- Atmospheric pressure
- Weather and moisture
- All of these
Correct answer: 4. All of these
Explanation:
SF6 belongs to the class of High Voltage Circuit breakers. At voltages 46 kV and above (classified as “high voltage” in the electrical power industry), the challenge of extinguishing the electric arc formed by separating breaker contacts becomes severe.
The gas inside the breaker’s tanks is sulfur hexafluoride, a very dense gas (about 5 times denser than air) with excellent electrical insulating and arc-extinguishing properties. SF6 gas is contained in these breaker contact chambers under pressure to maximize its dielectric breakdown strength (its ability to withstand high voltage without ionizing and passing current across the gap between the circuit breaker’s open contacts). SF6 gas is non-toxic and safe to handle. Continue reading here
Also see: Medium and Low Voltage Circuit breakers