0 Air Blast Circuit Breaker under the guidance of:- Presented By:- Mr. B.R.Reddy Anuj Kumar Pandey EN-3 rd year Roll No Unrestricted

 INTRODUCTION  CLASSIFICATION  ADVANTAGES  DISADVANTAGES  APPLICATIONS  FUTURE PERSPECTIVE

 An electrical power system is very complex. It needs some form of switchgear in order that it may be safely and efficiently controlled or regulated under both normal and abnormal operating conditions.  Circuit breaker is an automatically operated electrical switch.  It protects an electrical circuit from damage caused by overload and short circuit.  Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.

 Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.  It can be of various size, from small device that protects the appliances of an household to large to protect the entire city.

 FUNCTIONS:-  It carries the full load current continuously without over heating or damage.  It opens and closes the circuit on no load.  It makes and breaks the normal operating current.  It makes and breaks the short circuit current of magnitude up to which it is designed for.

 The circuit breaker can be classified on the basis of the quenching (cooling) medium: 1. Air circuit breaker 2. Air blast circuit breaker 3. Tank type bulk oil circuit breaker 4. Minimum oil circuit breaker 5. SF 6 circuit breaker 6. Vacuum circuit breaker

 AIRBLAST CIRCUIT BREAKER

 These type of breakers employ ‘air blast’ as the quenching medium.  The contacts are opened by air blast produced by the opening of blast valve.  The air blast cools the arc and sweeps away the arcing products to the atmosphere.  This rapidly increases the dielectric strength of the medium between contacts and prevents from re-establishing the arc.  So the arc is extinguished and the flow of current is interrupted. 8

 Types of Air blast circuit breaker (1). Axial-blast type (2).Cross-blast type (3).Radial-blast type

1) Axial-blast type:- In which the air-blast is directed along the arc path as shown in Fig. 10

In which the air-blast is directed at right angles to the arc path as shown in Fig. 11 2) Cross-blast type:-

In which the air-blast is directed radially as shown in Fig 12 (3) Radial-blast type:-

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 The risk of fire is eliminated.  The arcing products are completely removed by the blast  The growth of dielectric strength is so rapid that final contact gap needed for arc extinction is very small. This reduces the size of device.  The arcing time is very small due to the rapid build up of dielectric strength between contacts  Due to lesser arc energy, ABCB are very suitable for conditions where frequent operation is required  The energy supplied for arc extinction is obtained from high pressure air & independent of the current to be interrupted 15

 Air has relatively inferior arc extinguishing properties.  Air blast circuit breakers are very sensitive to the variations in the rate of restriking voltage.  Considerable maintenance is required for the compressor plant which supplies the air blast. 16

 The air blast circuit breakers are finding wide applications in high voltage installations. Majority of the circuit breakers for voltages beyond 110 kV are of this type. 17

◦ In the near future, present interrupting technologies can be applied to circuit-breakers with the higher rated breaking currents (63 kA to 80 kA) required in some networks with increasing power generation.

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