In Railway applications ______ circuit breaker is used.

The correct answer is: SF6.

SF6 circuit breakers are used in railway applications because they are very reliable and have a long life. They are also very fast, which is important in railway applications where there is a risk of derailment if the power is interrupted.

Bulk oil circuit breakers are not used in railway applications because they are too heavy and bulky. Minimum oil circuit breakers are not used in railway applications because they are not as reliable as SF6 circuit breakers. Air break circuit breakers are not used in railway applications because they are not as fast as SF6 circuit breakers.

Here is a brief description of each option:

• SF6 (sulfur hexafluoride) is a gas that is used in circuit breakers because it is very good at interrupting high currents. It is also non-flammable and non-toxic, which makes it safe to use in railway applications.
• Bulk oil circuit breakers use oil to extinguish the arc that is created when the circuit is interrupted. Oil is a good conductor of heat, which helps to cool the arc and prevent it from reigniting. However, bulk oil circuit breakers are very heavy and bulky, which makes them impractical for use in railway applications.
• Minimum oil circuit breakers use a small amount of oil to extinguish the arc. This makes them lighter and more compact than bulk oil circuit breakers, but they are not as reliable.
• Air break circuit breakers use air to extinguish the arc. Air is a good insulator, which makes it difficult for the arc to form. However, air break circuit breakers are not as fast as SF6 circuit breakers, and they are not as reliable in high-current applications.