In Railway applications ______ circuit breaker is used.
Right Answer is:
Air Blast Circuit Breaker
Air circuit breakers are normally only used at low voltage levels but are available with high current ratings up to 6,000 A and short circuit ratings up to 100 kA at 500 V. The physical size of such units, which contain large arc chutes, quickly makes them uneconomic as voltages increase above 3.6 kV.
The air-break circuit breakers are available in the range of 415 volts to 11 kV rating, the rated continuous current ranging from 100 to 4000 A and breaking current capacity up to 80000 A. As the name suggests, the insulation between the two contacts in air at normal temperature and pressure. The operating mechanism can be pneumatic, solenoid-operated or spring-operated. In the case of a spring-operated mechanism, the spring is to be charged by an induction motor (motor-operated spring mechanism). The performance and cost of the breaker are mainly decided by its breaking capacity. While breaking the fault currents, large electrodynamics forces are produced, not only due to high current but also due to the asymmetry of the fault current.
Application:- AC air-break circuit breakers are available in the voltage range 400 to 12 kV. They are widely used in low and medium-voltage systems. They are extensively used with electric furnaces, with large motors requiring frequent starting, in a place where chances of fire hazard exist, etc. Air-break circuit breakers are also used in dc circuits unto 12kV.
The air b circuit breakers are preferred for arc furnace duty and traction systems because they are suitable for repeated duty. These type of circuit breakers are finding their best application in systems operating in the range of 132 kV to 400 kV with breaker capacities upto 7000 MVA.