Course: Power System ProtectionCourse Code: EEE4277Presented by:Md. Tareq Hasan (ID-EEE233)Ambarish Biswas (ID-EEE188)Saifur Rahaman Russel (ID-EEE189)Md. Rumon Shaharier (ID-EEE186)Md. Mahazuddin Sarkar (ID-EEE192)

Air Blast Circuit Breaker

OVERVIEW

INTRODUCTIONCLASSIFICATIONCONSTRUCTIONOPERATIONADVANTAGEDISADVANTAGEAPPLICATIONSFUTURE PERSPECTIVE

INTRODUCTION This 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.

CLASSIFICATIONTypes 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.

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

3.Radial-blast type:-In which the air-blast is directed radialy as shown in Fig.

1.AXIAL BLAST ABCB

2.CROSS BLAST ABCB

CONSTRUCTION

In air blast circuit breaker (also called compressed air circuit breaker) high pressure air is forced on the arc through a nozzle at the instant of contact separation. The ionized medium between the contacts is blown away by the blast of the air. After the arc extinction the chamber is filled with high pressure air, which prevents restrike. In some low capacity circuit breakers, the isolator is an integral part of the circuit breaker. The circuit breaker opens and immediately after that the isolator opens, to provide addition gap.

OPERATION

AdvantagesThe risk of fire is eliminated.The arcing products are completely removed by 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 requised.

DisadvantagesAir has relatively inferior arc extinguishing properties.

Air blast circuit breakers are very sensitive to the variation is the rate of restriking voltage.

Considerable maintenance is required for the compressor plant which supplies the air blast.

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

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

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