What is Circuit Breaker?
A circuit breaker is a switching device that is used for protecting electrical equipment during fault conditions. A circuit breaker is used for closing and opening electrical circuits during fault conditions and also in normal conditions.
A circuit breaker is a mechanical switch that is interrupted by a high arc current during fault conditions and a normal current during the normal closing opening operations.
1. AC Circuit Breaker
2. DC Circuit Breaker
AC Circuit Breakers are classified on basis of medium of arc Extinction:
1. Air Break Circuit Breaker
2. Oil Circuit Breaker
1. Low oil Circuit Breaker
2. Bulk Oil Circuit Breaker
3. Air Blast Circuit Breaker
4. Sulphur hexafluoride Circuit Breaker
5. Vaccum Circuit Breaker
1. Air Break Circuit Breaker:
Air Circuit breakers use normal air as an arc extinction medium. In air Circuit Breaker arc is created in air and extinct in static air. this type of circuit breaker is used only for low voltage applications. Air break circuit breakers are used up to the voltage level of 15Kv. Air break circuit breakers interrupt 500MVA power during a fault condition it is called rupturing capacity of breaker.
Air Break Circuit Breaker further classified as
1. Plain Break type circuit Breker
This circuit breaker has the shape of contact-like arcing horns. Air is available between the two horns and horns have short distances at one point and long-distance at another point. when the arc is produced at a short distance between the horns, the air between horns goes upward due to the heating of air.
Arc is gone from one tip to another tip of horns when horns are fully separated resulting in lengthening and cooling the arc between the horns. These types of circuit breakers are used only for low voltage applications like miniature circuit breakers.
2. Magnetic Blow Out type Circuit Breaker
In these types of circuit breakers blow out the coil, Arc Shields, and arc chutes are used to extinguish the arc. Blow-out coils are connected in series with the circuit to be interrupted. The magnetic field is produced by a magnetic blow-out coil due to arc current.
The magnetic field can not extinguish the arc, it only moves the arc into arc chutes where the arc is cooled, lengthened, and extinguished. Arc shied prevent arc to spread in the nearby area.
3. Arc Chute Circuit Breaker
Arc chutes are parallel sets of metals plates arranged inside the circuit breaker main contacts. During fault conditions, contacts of the circuit breaker are separated and due to contacts separation, the arc is produced between the circuit breaker's main and fixed contacts. this arc produced a large amount of heat that is capable for melting circuit breaker contacts. so arc chutes are provided between the circuit breaker contacts.
Arc chutes plates are made from a ferromagnetic material and have equal distances between each other. the arc is attracted towards the arc chutes and then the arc is split into small parts. this will increase the length of the arc and cooled down the arc. arc chutes are used to save the circuit breaker main contacts to melt and safely extinguish the arc.
2. Oil Circuit Breakers
Oil Circuit Breakers are used dielectric oil as an arc extinction medium. Oil circuit breakers are subdivided into the 1. low oil circuit breakers and 2. Bulk oil Circuit Breakers.
1. Low Oil Circuit Breaker
In a Low oil circuit Breaker, the oil is used for arc extinction purposes by oil blast action in the arc extinction chamber, and oil is not used for insulating breaker live part from the earth.
In this type of circuit breaker, Arc extinction chambers are provided in Hollow porcelain insulators which insulates the breaker live parts from the earth.
These Circuit Breakers are used for voltage levels between 33Kv to 220Kv. Low oil circuit Breakers interrupt 1500MVA to 7500MVA power during a fault condition.
2. Bulk Oil Circuit breaker
In the Bulk oil circuit Breakers. Oil is used for arc extinction medium in arc extinction chamber and also oil acts as an insulating medium between the current-conducting parts to earthed tanks.
This Types of circuit breakers are used for voltage ranges between 2.5 kV to 230 kV. Bulk oil circuit breakers interrupt 25MVA to 5000MVA Power during a fault condition.
3. Air Blast Circuit Breaker
In an Airblast circuit Breaker, a high-pressure air blast is used for arc extinction. In an air blast circuit breaker, compressed air is stored in tanks, released through the high-pressure nozzle, and used for the extinction of arc in the arc extinction chamber.
Air Blast Circuit Breakers are used for indoor services and medium-high voltage applications. Airblast circuit breakers are used for voltages up to 15 Kv and interrupt 2500MVA power during the Fault conditions. This circuit breaker is now used for high voltage applications and used up to 220kv Voltages.
Air Blast Circuit Breakers are classified as
1. Axil blast circuit breaker
2. Cross blast circuit breaker
3. Radial blast circuit breaker
4. Sulphure hexafluoride circuit breaker
This type of circuit breaker used high-pressure gas as arc extinction medium in the arc extinction chamber. Sulphure hexafluoride gas has a high arc extinguishing property and higher dielectric strength than oil and air. Sulfur hexafluoride circuit breakers are used in very high voltage application voltage range 66kv to765kv.
5. Vaccum Circuit Breaker
In this type of circuit breaker fixed and moving contacts are sealed inside the high-pressure vacuum bottle. In this type of circuit breaker, a high-pressure vacuum is used as an arc extinction medium. The Vacuum pressure inside the vacuum chamber is 10-6 bar.
The vacuum circuit breaker is used for voltage ranges of 11kv to 33kv. Moving contacts of circuit breaker move from fixed contacts from 5 to 10 mm depending upon the voltage levels.
2. DC Circuit Breaker
A circuit Breaker used for interrupting high voltage direct current is called a DC circuit breaker. DC is unidirectional and zero point is not possible in the DC system. For interrupting fault current in DC circuit Breaker some External method required for reducing a DC current to Zero.